diff --git a/.gitignore b/.gitignore
index 7219675..253639d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,6 +21,7 @@
 shell_g
 /build/gyp
 /obj/
+/out/
 /test/es5conform/data/
 /test/mozilla/data/
 /test/sputnik/sputniktests/
@@ -31,5 +32,4 @@
 /tools/visual_studio/Release
 /xcodebuild/
 TAGS
-Makefile
 *.Makefile
diff --git a/Android.libv8.mk b/Android.libv8.mk
index e2978c7..96d632e 100644
--- a/Android.libv8.mk
+++ b/Android.libv8.mk
@@ -16,6 +16,7 @@
 # and V8_LOCAL_JS_LIBRARY_FILES
 V8_LOCAL_SRC_FILES :=
 V8_LOCAL_JS_LIBRARY_FILES :=
+V8_LOCAL_EXPERIMENTAL_JS_LIBRARY_FILES :=
 include $(LOCAL_PATH)/Android.v8common.mk
 
 # Target can only be linux
@@ -26,7 +27,7 @@
 LOCAL_SRC_FILES := $(V8_LOCAL_SRC_FILES)
 
 LOCAL_JS_LIBRARY_FILES := $(addprefix $(LOCAL_PATH)/, $(V8_LOCAL_JS_LIBRARY_FILES))
-LOCAL_JS_EXPERIMENTAL_LIBRARY_FILES := $(addprefix $(LOCAL_PATH)/, src/proxy.js)
+LOCAL_JS_EXPERIMENTAL_LIBRARY_FILES := $(addprefix $(LOCAL_PATH)/, $(V8_LOCAL_EXPERIMENTAL_JS_LIBRARY_FILES))
 
 # Copy js2c.py to intermediates directory and invoke there to avoid generating
 # jsmin.pyc in the source directory
diff --git a/Android.mksnapshot.mk b/Android.mksnapshot.mk
index 8f54be7..07da14b 100644
--- a/Android.mksnapshot.mk
+++ b/Android.mksnapshot.mk
@@ -12,6 +12,7 @@
 
 V8_LOCAL_SRC_FILES :=
 V8_LOCAL_JS_LIBRARY_FILES :=
+V8_LOCAL_JS_EXPERIMENTAL_LIBRARY_FILES :=
 include $(LOCAL_PATH)/Android.v8common.mk
 
 V8_LOCAL_SRC_FILES += \
@@ -33,7 +34,7 @@
 LOCAL_SRC_FILES := $(V8_LOCAL_SRC_FILES)
 
 LOCAL_JS_LIBRARY_FILES := $(addprefix $(LOCAL_PATH)/, $(V8_LOCAL_JS_LIBRARY_FILES))
-LOCAL_JS_EXPERIMENTAL_LIBRARY_FILES := $(addprefix $(LOCAL_PATH)/, src/proxy.js)
+LOCAL_JS_EXPERIMENTAL_LIBRARY_FILES := $(addprefix $(LOCAL_PATH)/, $(V8_LOCAL_EXPERIMENTAL_JS_LIBRARY_FILES))
 
 # Copy js2c.py to intermediates directory and invoke there to avoid generating
 # jsmin.pyc in the source directory
diff --git a/Android.v8common.mk b/Android.v8common.mk
index d318f0a..cb64a81 100644
--- a/Android.v8common.mk
+++ b/Android.v8common.mk
@@ -29,6 +29,7 @@
 	src/disassembler.cc \
 	src/diy-fp.cc \
 	src/dtoa.cc \
+	src/elements.cc \
 	src/execution.cc \
 	src/extensions/externalize-string-extension.cc \
 	src/extensions/gc-extension.cc \
@@ -136,7 +137,7 @@
 	src/uri.js \
 	src/math.js \
 	src/messages.js \
-	src/apinatives.js
+	src/apinatives.js 
 
 # These JS library sources must follow the above sources but their order is not
 # important.
@@ -150,3 +151,8 @@
 
 V8_LOCAL_JS_LIBRARY_FILES += \
 	src/macros.py
+
+V8_LOCAL_JS_EXPERIMENTAL_LIBRARY_FILES := \
+	src/proxy.js \
+	src/weakmap.js
+
diff --git a/ChangeLog b/ChangeLog
index 6901729..02d0ebb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,8 +1,134 @@
+2011-08-31: Version 3.5.10
+
+        Added dependency of v8_base on WinSocket2 Windows library in
+        the GYP-build.
+
+        Various bugfixes.
+
+
+2011-08-29: Version 3.5.9
+
+        Made FromPropertyDescriptor not trigger inherited setters.
+
+        Fixed .gyp files to work on the ARM simulator.
+
+        Fixed shared library build warnings for MSVS.
+
+
+2011-08-24: Version 3.5.8
+
+        Added V8EXPORT attributes for v8::Array::CheckCast and
+        v8::Number::CheckCast.
+
+        Made a slight API change enabling opting out from null termination
+        in String::Write*().
+
+        Fixed arm build for gcc-4.6.
+
+
+2011-08-22: Version 3.5.7
+
+        Make scanner handle invalid unicode escapes in identifiers correctly.
+
+        Make regexp flag parsing stricter.
+
+        Fix several memory leaks.
+
+
+2011-08-17: Version 3.5.6
+
+        Fixed issue that could cause crashes when running with --heap-stats.
+
+        Fixed compilation on Linux 2.6.9 and older.
+
+        Fixed live-object-list to work with isolates.
+
+        Fixed memory leaks in zones and isolates.
+
+        Fixed a performance regression for TypedArrays on x64.
+
+        Stability improvements on all platforms.
+
+
+2011-08-15: Version 3.5.5
+
+        Fixed bugs involving negative zero and the optimizing compiler.
+
+        Fixed optimized version of Function.apply(x, arguments). (issue 1592)
+
+        Eliminated uses of deprecated ARM instructions.
+
+        Sped up Math.floor by using SSE 4.1 roundsd instruction on ia32.
+
+        Removed restriction on the size of disassembled code that is printed.
+
+
+2011-08-10: Version 3.5.4
+
+        Added a preliminary implementation of ES Harmony weak maps.  Weak
+        maps can be enabled by the flag --harmony-weakmaps.
+
+        Introduced a toplevel Makefile to support GYP-based building.  GYP
+        can be obtained from http://gyp.googlecode.com.
+
+        Fixed a bug in the length property of functions created by
+        Function.prototype.bind.
+
+        Reduced malloc heap allocation on process startup.
+
+        Several important code generation bug fixes.
+
+        Performance improvements on all platforms.
+
+
+2011-08-03: Version 3.5.3
+
+        MIPS: Port of fix to ClassOf check from ARM.
+        Patch from Paul Lind <plind44@gmail.com>.
+
+        Stopped using mprotect on Cygwin.
+        Avoided uninitialized member warning on gcc 4.3.4
+        Both patches by Bert Belder.
+
+        Bug fixes and performance improvements on all platforms.
+
+
+2011-08-01: Version 3.5.2
+
+        Performance improvements on all platforms.
+
+
+2011-07-28: Version 3.5.1
+
+        Fixed setting the readonly flag on the prototype property using the
+        API call FunctionTemplate::SetPrototypeAttributes (issue 1539).
+
+        Changed the tools/test.py script to use d8 instead of shell for
+        testing.
+
+        Fixed crash in ToBooleanStub when GC happens during invocation.
+
+        Enabled automatic unboxing of double arrays.
+
+        Performance improvements on all platforms.
+
+
+2011-07-25: Version 3.5.0
+
+        Implemented Object.prototype.{hasOwnProperty, propertyIsEnumerable} for
+        proxies.
+
+        Removed logging to memory support.
+
+        Bugfixes and performance work.
+
+
 2011-07-20: Version 3.4.14
 
         Fix the debugger for strict-mode functions. (Chromium issue 89236)
 
-        Add GetPropertyAttribute method for Object in the API. (Patch by Peter Varga)
+        Add GetPropertyAttribute method for Object in the API. (Patch by 
+        Peter Varga)
 
         Fix -Wunused-but-set-variable for gcc-4.6 on x64. (Issue 1291)
 
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..3008779
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,171 @@
+# Copyright 2011 the V8 project authors. All rights reserved.
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+#     * Neither the name of Google Inc. nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+# Variable default definitions. Override them by exporting them in your shell.
+CXX ?= "g++"  # For distcc: export CXX="distcc g++"
+LINK ?= "g++"
+OUTDIR ?= out
+TESTJOBS ?= -j16
+GYPFLAGS ?=
+
+# Special build flags. Use them like this: "make library=shared"
+
+# library=shared || component=shared_library
+ifeq ($(library), shared)
+  GYPFLAGS += -Dcomponent=shared_library
+endif
+ifdef component
+  GYPFLAGS += -Dcomponent=$(component)
+endif
+# console=readline
+ifdef console
+  GYPFLAGS += -Dconsole=$(console)
+endif
+# disassembler=on
+ifeq ($(disassembler), on)
+  GYPFLAGS += -Dv8_enable_disassembler=1
+endif
+# snapshot=off
+ifeq ($(snapshot), off)
+  GYPFLAGS += -Dv8_use_snapshot='false'
+endif
+# gdbjit=on
+ifeq ($(gdbjit), on)
+  GYPFLAGS += -Dv8_enable_gdbjit=1
+endif
+# liveobjectlist=on
+ifeq ($(liveobjectlist), on)
+  GYPFLAGS += -Dv8_use_liveobjectlist=true
+endif
+# vfp3=off
+ifeq ($(vfp3), off)
+  GYPFLAGS += -Dv8_can_use_vfp_instructions=false
+else
+  GYPFLAGS += -Dv8_can_use_vfp_instructions=true
+endif
+
+# ----------------- available targets: --------------------
+# - any arch listed in ARCHES (see below)
+# - any mode listed in MODES
+# - every combination <arch>.<mode>, e.g. "ia32.release"
+# - any of the above with .check appended, e.g. "ia32.release.check"
+# - default (no target specified): build all ARCHES and MODES
+# - "check": build all targets and run all tests
+# - "<arch>.clean" for any <arch> in ARCHES
+# - "clean": clean all ARCHES
+
+# ----------------- internal stuff ------------------------
+
+# Architectures and modes to be compiled. Consider these to be internal
+# variables, don't override them (use the targets instead).
+ARCHES = ia32 x64 arm
+MODES = release debug
+
+# List of files that trigger Makefile regeneration:
+GYPFILES = build/all.gyp build/common.gypi build/standalone.gypi \
+           preparser/preparser.gyp samples/samples.gyp src/d8.gyp \
+           test/cctest/cctest.gyp tools/gyp/v8.gyp
+
+# Generates all combinations of ARCHES and MODES, e.g. "ia32.release".
+BUILDS = $(foreach mode,$(MODES),$(addsuffix .$(mode),$(ARCHES)))
+# Generates corresponding test targets, e.g. "ia32.release.check".
+CHECKS = $(addsuffix .check,$(BUILDS))
+# File where previously used GYPFLAGS are stored.
+ENVFILE = $(OUTDIR)/environment
+
+.PHONY: all clean $(ENVFILE).new \
+        $(ARCHES) $(MODES) $(BUILDS) $(addsuffix .clean,$(ARCHES))
+
+# Target definitions. "all" is the default.
+all: $(MODES)
+
+# Compile targets. MODES and ARCHES are convenience targets.
+.SECONDEXPANSION:
+$(MODES): $(addsuffix .$$@,$(ARCHES))
+
+$(ARCHES): $(addprefix $$@.,$(MODES))
+
+# Defines how to build a particular target (e.g. ia32.release).
+$(BUILDS): $(OUTDIR)/Makefile-$$(basename $$@)
+	@$(MAKE) -C "$(OUTDIR)" -f Makefile-$(basename $@) \
+	         CXX="$(CXX)" LINK="$(LINK)" \
+	         BUILDTYPE=$(shell echo $(subst .,,$(suffix $@)) | \
+	                     python -c "print raw_input().capitalize()") \
+	         builddir="$(shell pwd)/$(OUTDIR)/$@"
+
+# Test targets.
+check: all
+	@tools/test-wrapper-gypbuild.py $(TESTJOBS) --outdir=$(OUTDIR)
+
+$(addsuffix .check,$(MODES)): $$(basename $$@)
+	@tools/test-wrapper-gypbuild.py $(TESTJOBS) --outdir=$(OUTDIR) \
+	    --mode=$(basename $@)
+
+$(addsuffix .check,$(ARCHES)): $$(basename $$@)
+	@tools/test-wrapper-gypbuild.py $(TESTJOBS) --outdir=$(OUTDIR) \
+	    --arch=$(basename $@)
+
+$(CHECKS): $$(basename $$@)
+	@tools/test-wrapper-gypbuild.py $(TESTJOBS) --outdir=$(OUTDIR) \
+	    --arch-and-mode=$(basename $@)
+
+# Clean targets. You can clean each architecture individually, or everything.
+$(addsuffix .clean,$(ARCHES)):
+	rm -f $(OUTDIR)/Makefile-$(basename $@)
+	rm -rf $(OUTDIR)/$(basename $@).release
+	rm -rf $(OUTDIR)/$(basename $@).debug
+	find $(OUTDIR) -regex '.*\(host\|target\)-$(basename $@)\.mk' -delete
+
+clean: $(addsuffix .clean,$(ARCHES))
+
+# GYP file generation targets.
+$(OUTDIR)/Makefile-ia32: $(GYPFILES) $(ENVFILE)
+	build/gyp/gyp --generator-output="$(OUTDIR)" build/all.gyp \
+	              -Ibuild/standalone.gypi --depth=. -Dtarget_arch=ia32 \
+	              -S-ia32 $(GYPFLAGS)
+
+$(OUTDIR)/Makefile-x64: $(GYPFILES) $(ENVFILE)
+	build/gyp/gyp --generator-output="$(OUTDIR)" build/all.gyp \
+	              -Ibuild/standalone.gypi --depth=. -Dtarget_arch=x64 \
+	              -S-x64 $(GYPFLAGS)
+
+$(OUTDIR)/Makefile-arm: $(GYPFILES) $(ENVFILE)
+	build/gyp/gyp --generator-output="$(OUTDIR)" build/all.gyp \
+	              -Ibuild/standalone.gypi --depth=. -Ibuild/armu.gypi \
+	              -S-arm $(GYPFLAGS)
+
+# Replaces the old with the new environment file if they're different, which
+# will trigger GYP to regenerate Makefiles.
+$(ENVFILE): $(ENVFILE).new
+	@if test -r $(ENVFILE) && cmp $(ENVFILE).new $(ENVFILE) >/dev/null; \
+	    then rm $(ENVFILE).new; \
+	    else mv $(ENVFILE).new $(ENVFILE); fi
+
+# Stores current GYPFLAGS in a file.
+$(ENVFILE).new:
+	@mkdir -p $(OUTDIR); echo "GYPFLAGS=$(GYPFLAGS)" > $(ENVFILE).new;
diff --git a/SConstruct b/SConstruct
index 8e16a78..f9c33ca 100644
--- a/SConstruct
+++ b/SConstruct
@@ -153,13 +153,19 @@
         }
       },
       'armeabi:softfp' : {
-        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=0', 'CAN_USE_VFP_INSTRUCTIONS'],
+        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=0'],
+        'vfp3:on': {
+          'CPPDEFINES' : ['CAN_USE_VFP_INSTRUCTIONS']
+        },
         'simulator:none': {
           'CCFLAGS':     ['-mfloat-abi=softfp'],
         }
       },
       'armeabi:hard' : {
-        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1', 'CAN_USE_VFP_INSTRUCTIONS'],
+        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1'],
+        'vfp3:on': {
+          'CPPDEFINES' : ['CAN_USE_VFP_INSTRUCTIONS']
+        },
         'simulator:none': {
           'CCFLAGS':     ['-mfloat-abi=hard'],
         }
@@ -436,7 +442,7 @@
     },
     'arch:x64': {
       'CPPDEFINES':   ['V8_TARGET_ARCH_X64'],
-      'LINKFLAGS': ['/STACK:2091752']
+      'LINKFLAGS': ['/STACK:2097152']
     },
   }
 }
@@ -496,7 +502,10 @@
         }
       },
       'armeabi:hard' : {
-        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1', 'CAN_USE_VFP_INSTRUCTIONS'],
+        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1'],
+        'vfp3:on': {
+          'CPPDEFINES' : ['CAN_USE_VFP_INSTRUCTIONS']
+        },
         'simulator:none': {
           'CCFLAGS':     ['-mfloat-abi=hard'],
         }
@@ -601,7 +610,7 @@
     },
     'arch:x64': {
       'CPPDEFINES': ['V8_TARGET_ARCH_X64', 'WIN32'],
-      'LINKFLAGS': ['/MACHINE:X64', '/STACK:2091752']
+      'LINKFLAGS': ['/MACHINE:X64', '/STACK:2097152']
     },
     'mode:debug': {
       'CCFLAGS':    ['/Od'],
@@ -756,7 +765,7 @@
     },
     'arch:x64': {
       'CPPDEFINES': ['V8_TARGET_ARCH_X64', 'WIN32'],
-      'LINKFLAGS': ['/MACHINE:X64', '/STACK:2091752']
+      'LINKFLAGS': ['/MACHINE:X64', '/STACK:2097152']
     },
     'mode:debug': {
       'CCFLAGS':    ['/Od'],
@@ -822,6 +831,57 @@
   'msvc': {
     'all': {
       'LIBS': ['winmm', 'ws2_32']
+    },
+    'verbose:off': {
+      'CCFLAGS': ['/nologo'],
+      'LINKFLAGS': ['/NOLOGO']
+    },
+    'verbose:on': {
+      'LINKFLAGS': ['/VERBOSE']
+    },
+    'prof:on': {
+      'LINKFLAGS': ['/MAP']
+    },
+    'mode:release': {
+      'CCFLAGS':   ['/O2'],
+      'LINKFLAGS': ['/OPT:REF', '/OPT:ICF'],
+      'msvcrt:static': {
+        'CCFLAGS': ['/MT']
+      },
+      'msvcrt:shared': {
+        'CCFLAGS': ['/MD']
+      },
+      'msvcltcg:on': {
+        'CCFLAGS':      ['/GL'],
+        'pgo:off': {
+          'LINKFLAGS':    ['/LTCG'],
+        },
+      },
+      'pgo:instrument': {
+        'LINKFLAGS':    ['/LTCG:PGI']
+      },
+      'pgo:optimize': {
+        'LINKFLAGS':    ['/LTCG:PGO']
+      }
+    },
+    'arch:ia32': {
+      'CPPDEFINES': ['V8_TARGET_ARCH_IA32', 'WIN32'],
+      'LINKFLAGS': ['/MACHINE:X86']
+    },
+    'arch:x64': {
+      'CPPDEFINES': ['V8_TARGET_ARCH_X64', 'WIN32'],
+      'LINKFLAGS': ['/MACHINE:X64', '/STACK:2097152']
+    },
+    'mode:debug': {
+      'CCFLAGS':    ['/Od'],
+      'LINKFLAGS':  ['/DEBUG'],
+      'CPPDEFINES': ['DEBUG'],
+      'msvcrt:static': {
+        'CCFLAGS':  ['/MTd']
+      },
+      'msvcrt:shared': {
+        'CCFLAGS':  ['/MDd']
+      }
     }
   }
 }
@@ -1039,6 +1099,12 @@
     'default': 'off',
     'help': 'compress startup data (snapshot) [Linux only]'
   },
+  'vfp3': {
+    'values': ['on', 'off'],
+    'default': 'on',
+    'help': 'use vfp3 instructions when building the snapshot [Arm only]'
+  },
+
 }
 
 ALL_OPTIONS = dict(PLATFORM_OPTIONS, **SIMPLE_OPTIONS)
@@ -1343,10 +1409,12 @@
     env['SONAME'] = soname
 
   # Build the object files by invoking SCons recursively.
+  d8_env = Environment(tools=tools)
+  d8_env.Replace(**context.flags['d8'])
   (object_files, shell_files, mksnapshot, preparser_files) = env.SConscript(
     join('src', 'SConscript'),
     build_dir=join('obj', target_id),
-    exports='context tools',
+    exports='context tools d8_env',
     duplicate=False
   )
 
@@ -1375,8 +1443,6 @@
   context.library_targets.append(library)
   context.library_targets.append(preparser_library)
 
-  d8_env = Environment(tools=tools)
-  d8_env.Replace(**context.flags['d8'])
   context.ApplyEnvOverrides(d8_env)
   if context.options['library'] == 'static':
     shell = d8_env.Program('d8' + suffix, object_files + shell_files)
diff --git a/V8_MERGE_REVISION b/V8_MERGE_REVISION
index ff5fd5d..8caa544 100644
--- a/V8_MERGE_REVISION
+++ b/V8_MERGE_REVISION
@@ -1,2 +1,2 @@
-V8 3.4.14.35
-http://v8.googlecode.com/svn/branches/3.4@9839
+V8 3.5.10.24
+http://v8.googlecode.com/svn/branches/3.5@9918
diff --git a/build/all.gyp b/build/all.gyp
index 38287e3..9c0f05c 100644
--- a/build/all.gyp
+++ b/build/all.gyp
@@ -1,4 +1,4 @@
-# Copyright (c) 2010 The Chromium Authors. All rights reserved.
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -8,6 +8,7 @@
       'target_name': 'All',
       'type': 'none',
       'dependencies': [
+        '../preparser/preparser.gyp:*',
         '../samples/samples.gyp:*',
         '../src/d8.gyp:d8',
       ],
diff --git a/build/armu.gypi b/build/armu.gypi
index 3f874c0..d15b8ab 100644
--- a/build/armu.gypi
+++ b/build/armu.gypi
@@ -32,5 +32,5 @@
     'armv7': 1,
     'arm_neon': 0,
     'arm_fpu': 'vfpv3',
-  }
+  },
 }
diff --git a/build/common.gypi b/build/common.gypi
index 7020495..834516f 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -1,4 +1,4 @@
-# Copyright 2010 the V8 project authors. All rights reserved.
+# Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
@@ -25,159 +25,266 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+# Shared definitions for all V8-related targets.
+
 {
   'variables': {
-    'library%': 'static_library',
-    'component%': 'static_library',
-    'visibility%': 'hidden',
-    'variables': {
-      'conditions': [
-        [ 'OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
-          # This handles the Linux platforms we generally deal with. Anything
-          # else gets passed through, which probably won't work very well; such
-          # hosts should pass an explicit target_arch to gyp.
-          'host_arch%':
-            '<!(uname -m | sed -e "s/i.86/ia32/;s/x86_64/x64/;s/amd64/x64/;s/arm.*/arm/")',
-        }, {  # OS!="linux" and OS!="freebsd" and OS!="openbsd"
-          'host_arch%': 'ia32',
-        }],
-      ],
-    },
-    'host_arch%': '<(host_arch)',
-    'target_arch%': '<(host_arch)',
+    'use_system_v8%': 0,
+    'msvs_use_common_release': 0,
+    'gcc_version%': 'unknown',
+    'v8_compress_startup_data%': 'off',
     'v8_target_arch%': '<(target_arch)',
+
+    # Setting 'v8_can_use_unaligned_accesses' to 'true' will allow the code
+    # generated by V8 to do unaligned memory access, and setting it to 'false'
+    # will ensure that the generated code will always do aligned memory
+    # accesses. The default value of 'default' will try to determine the correct
+    # setting. Note that for Intel architectures (ia32 and x64) unaligned memory
+    # access is allowed for all CPUs.
+    'v8_can_use_unaligned_accesses%': 'default',
+
+    # Setting 'v8_can_use_vfp_instructions' to 'true' will enable use of ARM VFP
+    # instructions in the V8 generated code. VFP instructions will be enabled
+    # both for the snapshot and for the ARM target. Leaving the default value
+    # of 'false' will avoid VFP instructions in the snapshot and use CPU feature
+    # probing when running on the target.
+    'v8_can_use_vfp_instructions%': 'false',
+
+    # Setting v8_use_arm_eabi_hardfloat to true will turn on V8 support for ARM
+    # EABI calling convention where double arguments are passed in VFP
+    # registers. Note that the GCC flag '-mfloat-abi=hard' should be used as
+    # well when compiling for the ARM target.
+    'v8_use_arm_eabi_hardfloat%': 'false',
+
+    'v8_enable_debugger_support%': 1,
+
+    'v8_enable_disassembler%': 0,
+
+    'v8_enable_gdbjit%': 0,
+
+    # Enable profiling support. Only required on Windows.
+    'v8_enable_prof%': 0,
+
+    # Chrome needs this definition unconditionally. For standalone V8 builds,
+    # it's handled in build/standalone.gypi.
+    'want_separate_host_toolset%': 1,
+
+    'v8_use_snapshot%': 'true',
+    'host_os%': '<(OS)',
+    'v8_use_liveobjectlist%': 'false',
   },
   'target_defaults': {
-    'default_configuration': 'Debug',
+    'conditions': [
+      ['v8_enable_debugger_support==1', {
+        'defines': ['ENABLE_DEBUGGER_SUPPORT',],
+      }],
+      ['v8_enable_disassembler==1', {
+        'defines': ['ENABLE_DISASSEMBLER',],
+      }],
+      ['v8_enable_gdbjit==1', {
+        'defines': ['ENABLE_GDB_JIT_INTERFACE',],
+      }],
+      ['OS!="mac"', {
+        # TODO(mark): The OS!="mac" conditional is temporary. It can be
+        # removed once the Mac Chromium build stops setting target_arch to
+        # ia32 and instead sets it to mac. Other checks in this file for
+        # OS=="mac" can be removed at that time as well. This can be cleaned
+        # up once http://crbug.com/44205 is fixed.
+        'conditions': [
+          ['v8_target_arch=="arm"', {
+            'defines': [
+              'V8_TARGET_ARCH_ARM',
+            ],
+            'conditions': [
+              [ 'v8_can_use_unaligned_accesses=="true"', {
+                'defines': [
+                  'CAN_USE_UNALIGNED_ACCESSES=1',
+                ],
+              }],
+              [ 'v8_can_use_unaligned_accesses=="false"', {
+                'defines': [
+                  'CAN_USE_UNALIGNED_ACCESSES=0',
+                ],
+              }],
+              [ 'v8_can_use_vfp_instructions=="true"', {
+                'defines': [
+                  'CAN_USE_VFP_INSTRUCTIONS',
+                ],
+              }],
+              [ 'v8_use_arm_eabi_hardfloat=="true"', {
+                'defines': [
+                  'USE_EABI_HARDFLOAT=1',
+                  'CAN_USE_VFP_INSTRUCTIONS',
+                ],
+                'cflags': [
+                  '-mfloat-abi=hard',
+                ],
+              }, {
+                'defines': [
+                  'USE_EABI_HARDFLOAT=0',
+                ],
+              }],
+              # The ARM assembler assumes the host is 32 bits,
+              # so force building 32-bit host tools.
+              ['host_arch=="x64"', {
+                'target_conditions': [
+                  ['_toolset=="host"', {
+                    'cflags': ['-m32'],
+                    'ldflags': ['-m32'],
+                  }],
+                ],
+              }],
+            ],
+          }],
+          ['v8_target_arch=="ia32"', {
+            'defines': [
+              'V8_TARGET_ARCH_IA32',
+            ],
+          }],
+          ['v8_target_arch=="mips"', {
+            'defines': [
+              'V8_TARGET_ARCH_MIPS',
+            ],
+          }],
+          ['v8_target_arch=="x64"', {
+            'defines': [
+              'V8_TARGET_ARCH_X64',
+            ],
+          }],
+        ],
+      }],
+      ['v8_use_liveobjectlist=="true"', {
+        'defines': [
+          'ENABLE_DEBUGGER_SUPPORT',
+          'INSPECTOR',
+          'OBJECT_PRINT',
+          'LIVEOBJECTLIST',
+        ],
+      }],
+      ['v8_compress_startup_data=="bz2"', {
+        'defines': [
+          'COMPRESS_STARTUP_DATA_BZ2',
+        ],
+      }],
+      ['OS=="win" and v8_enable_prof==1', {
+        'msvs_settings': {
+          'VCLinkerTool': {
+            'GenerateMapFile': 'true',
+          },
+        },
+      }],
+    ],
     'configurations': {
       'Debug': {
-        'cflags': [ '-g', '-O0' ],
-        'defines': [ 'ENABLE_DISASSEMBLER', 'DEBUG' ],
+        'defines': [
+          'DEBUG',
+          'ENABLE_DISASSEMBLER',
+          'V8_ENABLE_CHECKS',
+          'OBJECT_PRINT',
+        ],
+        'msvs_settings': {
+          'VCCLCompilerTool': {
+            'Optimization': '0',
+
+            'conditions': [
+              ['OS=="win" and component=="shared_library"', {
+                'RuntimeLibrary': '3',  # /MDd
+              }, {
+                'RuntimeLibrary': '1',  # /MTd
+              }],
+            ],
+          },
+          'VCLinkerTool': {
+            'LinkIncremental': '2',
+            # For future reference, the stack size needs to be increased
+            # when building for Windows 64-bit, otherwise some test cases
+            # can cause stack overflow.
+            # 'StackReserveSize': '297152',
+          },
+        },
+        'conditions': [
+          ['OS=="freebsd" or OS=="openbsd"', {
+            'cflags': [ '-I/usr/local/include' ],
+          }],
+          ['OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
+            'cflags': [ '-Wall', '-Werror', '-W', '-Wno-unused-parameter',
+                        '-Wnon-virtual-dtor' ],
+          }],
+        ],
       },
       'Release': {
-        'cflags': [ '-O3', '-fomit-frame-pointer', '-fdata-sections', '-ffunction-sections' ],
+        'conditions': [
+          ['OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
+            'cflags!': [
+              '-O2',
+              '-Os',
+            ],
+            'cflags': [
+              '-fdata-sections',
+              '-ffunction-sections',
+              '-fomit-frame-pointer',
+              '-O3',
+            ],
+            'conditions': [
+              [ 'gcc_version==44', {
+                'cflags': [
+                  # Avoid crashes with gcc 4.4 in the v8 test suite.
+                  '-fno-tree-vrp',
+                ],
+              }],
+            ],
+          }],
+          ['OS=="freebsd" or OS=="openbsd"', {
+            'cflags': [ '-I/usr/local/include' ],
+          }],
+          ['OS=="mac"', {
+            'xcode_settings': {
+              'GCC_OPTIMIZATION_LEVEL': '3',  # -O3
+
+              # -fstrict-aliasing.  Mainline gcc
+              # enables this at -O2 and above,
+              # but Apple gcc does not unless it
+              # is specified explicitly.
+              'GCC_STRICT_ALIASING': 'YES',
+            },
+          }],
+          ['OS=="win"', {
+            'msvs_configuration_attributes': {
+              'OutputDirectory': '$(SolutionDir)$(ConfigurationName)',
+              'IntermediateDirectory': '$(OutDir)\\obj\\$(ProjectName)',
+              'CharacterSet': '1',
+            },
+            'msvs_settings': {
+              'VCCLCompilerTool': {
+                'Optimization': '2',
+                'InlineFunctionExpansion': '2',
+                'EnableIntrinsicFunctions': 'true',
+                'FavorSizeOrSpeed': '0',
+                'OmitFramePointers': 'true',
+                'StringPooling': 'true',
+
+                'conditions': [
+                  ['OS=="win" and component=="shared_library"', {
+                    'RuntimeLibrary': '2',  #/MD
+                  }, {
+                    'RuntimeLibrary': '0',  #/MT
+                  }],
+                ],
+              },
+              'VCLinkerTool': {
+                'LinkIncremental': '1',
+                'OptimizeReferences': '2',
+                'OptimizeForWindows98': '1',
+                'EnableCOMDATFolding': '2',
+                # For future reference, the stack size needs to be
+                # increased when building for Windows 64-bit, otherwise
+                # some test cases can cause stack overflow.
+                # 'StackReserveSize': '297152',
+              },
+            },
+          }],
+        ],
       },
     },
   },
-  'conditions': [
-    [ 'OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"', {
-      'target_defaults': {
-        'cflags': [ '-Wall', '-pthread', '-fno-rtti', '-fno-exceptions' ],
-        'ldflags': [ '-pthread', ],
-        'conditions': [
-          [ 'target_arch=="ia32"', {
-            'cflags': [ '-m32' ],
-            'ldflags': [ '-m32' ],
-          }],
-          [ 'OS=="linux"', {
-            'cflags': [ '-ansi' ],
-          }],
-          [ 'visibility=="hidden"', {
-            'cflags': [ '-fvisibility=hidden' ],
-          }],
-        ],
-      },
-    }],  # 'OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"'
-    ['OS=="win"', {
-      'target_defaults': {
-        'defines': [
-          'WIN32',
-          '_CRT_SECURE_NO_DEPRECATE',
-          '_CRT_NONSTDC_NO_DEPRECATE',
-        ],
-        'conditions': [
-          ['component=="static_library"', {
-            'defines': [
-              '_HAS_EXCEPTIONS=0',
-            ],
-          }],
-        ],        
-        'msvs_cygwin_dirs': ['<(DEPTH)/third_party/cygwin'],
-        'msvs_disabled_warnings': [4355, 4800],
-        'msvs_settings': {
-          'VCCLCompilerTool': {
-            'MinimalRebuild': 'false',
-            'BufferSecurityCheck': 'true',
-            'EnableFunctionLevelLinking': 'true',
-            'RuntimeTypeInfo': 'false',
-            'WarningLevel': '3',
-            'WarnAsError': 'true',
-            'DebugInformationFormat': '3',
-            'Detect64BitPortabilityProblems': 'false',
-            'conditions': [
-              [ 'msvs_multi_core_compile', {
-                'AdditionalOptions': ['/MP'],
-              }],
-              ['component=="shared_library"', {
-                'ExceptionHandling': '1',  # /EHsc
-              }, {
-                'ExceptionHandling': '0',
-              }],
-            ],
-          },
-          'VCLibrarianTool': {
-            'AdditionalOptions': ['/ignore:4221'],
-          },
-          'VCLinkerTool': {
-            'AdditionalDependencies': [
-              'ws2_32.lib',
-            ],
-            'GenerateDebugInformation': 'true',
-            'MapFileName': '$(OutDir)\\$(TargetName).map',
-            'ImportLibrary': '$(OutDir)\\lib\\$(TargetName).lib',
-            'FixedBaseAddress': '1',
-            # LinkIncremental values:
-            #   0 == default
-            #   1 == /INCREMENTAL:NO
-            #   2 == /INCREMENTAL
-            'LinkIncremental': '1',
-            # SubSystem values:
-            #   0 == not set
-            #   1 == /SUBSYSTEM:CONSOLE
-            #   2 == /SUBSYSTEM:WINDOWS
-            'SubSystem': '1',
-          },
-        },
-      },
-    }],  # OS=="win"
-    ['OS=="mac"', {
-      'target_defaults': {
-        'xcode_settings': {
-          'ALWAYS_SEARCH_USER_PATHS': 'NO',
-          'GCC_C_LANGUAGE_STANDARD': 'ansi',        # -ansi
-          'GCC_CW_ASM_SYNTAX': 'NO',                # No -fasm-blocks
-          'GCC_DYNAMIC_NO_PIC': 'NO',               # No -mdynamic-no-pic
-                                                    # (Equivalent to -fPIC)
-          'GCC_ENABLE_CPP_EXCEPTIONS': 'NO',        # -fno-exceptions
-          'GCC_ENABLE_CPP_RTTI': 'NO',              # -fno-rtti
-          'GCC_ENABLE_PASCAL_STRINGS': 'NO',        # No -mpascal-strings
-          # GCC_INLINES_ARE_PRIVATE_EXTERN maps to -fvisibility-inlines-hidden
-          'GCC_INLINES_ARE_PRIVATE_EXTERN': 'YES',
-          'GCC_SYMBOLS_PRIVATE_EXTERN': 'YES',      # -fvisibility=hidden
-          'GCC_THREADSAFE_STATICS': 'NO',           # -fno-threadsafe-statics
-          'GCC_TREAT_WARNINGS_AS_ERRORS': 'YES',    # -Werror
-          'GCC_VERSION': '4.2',
-          'GCC_WARN_ABOUT_MISSING_NEWLINE': 'YES',  # -Wnewline-eof
-          'MACOSX_DEPLOYMENT_TARGET': '10.4',       # -mmacosx-version-min=10.4
-          'PREBINDING': 'NO',                       # No -Wl,-prebind
-          'USE_HEADERMAP': 'NO',
-          'OTHER_CFLAGS': [
-            '-fno-strict-aliasing',
-          ],
-          'WARNING_CFLAGS': [
-            '-Wall',
-            '-Wendif-labels',
-            '-W',
-            '-Wno-unused-parameter',
-            '-Wnon-virtual-dtor',
-          ],
-        },
-        'target_conditions': [
-          ['_type!="static_library"', {
-            'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
-          }],
-        ],  # target_conditions
-      },  # target_defaults
-    }],  # OS=="mac"
-  ],
 }
diff --git a/build/gyp_v8 b/build/gyp_v8
index 61b54c2..dfdbe3f 100755
--- a/build/gyp_v8
+++ b/build/gyp_v8
@@ -92,8 +92,8 @@
     if os.path.realpath(path) not in specified_includes:
       result.append(path)
 
-  # Always include common.gypi & features_override.gypi
-  AddInclude(os.path.join(script_dir, 'common.gypi'))
+  # Always include standalone.gypi
+  AddInclude(os.path.join(script_dir, 'standalone.gypi'))
 
   # Optionally add supplemental .gypi files if present.
   supplements = glob.glob(os.path.join(v8_root, '*', 'supplement.gypi'))
diff --git a/build/standalone.gypi b/build/standalone.gypi
new file mode 100644
index 0000000..81909f1
--- /dev/null
+++ b/build/standalone.gypi
@@ -0,0 +1,200 @@
+# Copyright 2011 the V8 project authors. All rights reserved.
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+#     * Neither the name of Google Inc. nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# Definitions to be used when building stand-alone V8 binaries.
+
+{
+  'variables': {
+    'library%': 'static_library',
+    'component%': 'static_library',
+    'visibility%': 'hidden',
+    'msvs_multi_core_compile%': '1',
+    'variables': {
+      'variables': {
+        'conditions': [
+          [ 'OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
+            # This handles the Linux platforms we generally deal with. Anything
+            # else gets passed through, which probably won't work very well; such
+            # hosts should pass an explicit target_arch to gyp.
+            'host_arch%':
+              '<!(uname -m | sed -e "s/i.86/ia32/;s/x86_64/x64/;s/amd64/x64/;s/arm.*/arm/")',
+          }, {  # OS!="linux" and OS!="freebsd" and OS!="openbsd"
+            'host_arch%': 'ia32',
+          }],
+        ],
+      },
+      'host_arch%': '<(host_arch)',
+      'target_arch%': '<(host_arch)',
+      'v8_target_arch%': '<(target_arch)',
+    },
+    'host_arch%': '<(host_arch)',
+    'target_arch%': '<(target_arch)',
+    'v8_target_arch%': '<(v8_target_arch)',
+    'conditions': [
+      ['(v8_target_arch=="arm" and host_arch!="arm") or \
+        (v8_target_arch=="x64" and host_arch!="x64")', {
+        'want_separate_host_toolset': 1,
+      }, {
+        'want_separate_host_toolset': 0,
+      }],
+    ],
+  },
+  'target_defaults': {
+    'default_configuration': 'Debug',
+    'configurations': {
+      'Debug': {
+        'cflags': [ '-g', '-O0' ],
+      },
+    },
+  },
+  'conditions': [
+    [ 'OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"', {
+      'target_defaults': {
+        'cflags': [ '-Wall', '-Werror', '-W', '-Wno-unused-parameter',
+                    '-Wnon-virtual-dtor', '-pthread', '-fno-rtti',
+                    '-fno-exceptions', '-pedantic' ],
+        'ldflags': [ '-pthread', ],
+        'conditions': [
+          [ 'target_arch=="ia32"', {
+            'cflags': [ '-m32' ],
+            'ldflags': [ '-m32' ],
+          }],
+          [ 'OS=="linux"', {
+            'cflags': [ '-ansi' ],
+          }],
+          [ 'visibility=="hidden"', {
+            'cflags': [ '-fvisibility=hidden' ],
+          }],
+          [ 'component=="shared_library"', {
+            'cflags': [ '-fPIC', ],
+          }],
+        ],
+      },
+    }],  # 'OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"'
+    ['OS=="win"', {
+      'target_defaults': {
+        'defines': [
+          'WIN32',
+          '_CRT_SECURE_NO_DEPRECATE',
+          '_CRT_NONSTDC_NO_DEPRECATE',
+        ],
+        'conditions': [
+          ['component=="static_library"', {
+            'defines': [
+              '_HAS_EXCEPTIONS=0',
+            ],
+          }],
+        ],
+        'msvs_cygwin_dirs': ['<(DEPTH)/third_party/cygwin'],
+        'msvs_disabled_warnings': [4355, 4800],
+        'msvs_settings': {
+          'VCCLCompilerTool': {
+            'MinimalRebuild': 'false',
+            'BufferSecurityCheck': 'true',
+            'EnableFunctionLevelLinking': 'true',
+            'RuntimeTypeInfo': 'false',
+            'WarningLevel': '3',
+            'WarnAsError': 'true',
+            'DebugInformationFormat': '3',
+            'Detect64BitPortabilityProblems': 'false',
+            'conditions': [
+              [ 'msvs_multi_core_compile', {
+                'AdditionalOptions': ['/MP'],
+              }],
+              ['component=="shared_library"', {
+                'ExceptionHandling': '1',  # /EHsc
+              }, {
+                'ExceptionHandling': '0',
+              }],
+            ],
+          },
+          'VCLibrarianTool': {
+            'AdditionalOptions': ['/ignore:4221'],
+          },
+          'VCLinkerTool': {
+            'AdditionalDependencies': [
+              'ws2_32.lib',
+            ],
+            'GenerateDebugInformation': 'true',
+            'MapFileName': '$(OutDir)\\$(TargetName).map',
+            'ImportLibrary': '$(OutDir)\\lib\\$(TargetName).lib',
+            'FixedBaseAddress': '1',
+            # LinkIncremental values:
+            #   0 == default
+            #   1 == /INCREMENTAL:NO
+            #   2 == /INCREMENTAL
+            'LinkIncremental': '1',
+            # SubSystem values:
+            #   0 == not set
+            #   1 == /SUBSYSTEM:CONSOLE
+            #   2 == /SUBSYSTEM:WINDOWS
+            'SubSystem': '1',
+          },
+        },
+      },
+    }],  # OS=="win"
+    ['OS=="mac"', {
+      'target_defaults': {
+        'xcode_settings': {
+          'ALWAYS_SEARCH_USER_PATHS': 'NO',
+          'GCC_C_LANGUAGE_STANDARD': 'ansi',        # -ansi
+          'GCC_CW_ASM_SYNTAX': 'NO',                # No -fasm-blocks
+          'GCC_DYNAMIC_NO_PIC': 'NO',               # No -mdynamic-no-pic
+                                                    # (Equivalent to -fPIC)
+          'GCC_ENABLE_CPP_EXCEPTIONS': 'NO',        # -fno-exceptions
+          'GCC_ENABLE_CPP_RTTI': 'NO',              # -fno-rtti
+          'GCC_ENABLE_PASCAL_STRINGS': 'NO',        # No -mpascal-strings
+          # GCC_INLINES_ARE_PRIVATE_EXTERN maps to -fvisibility-inlines-hidden
+          'GCC_INLINES_ARE_PRIVATE_EXTERN': 'YES',
+          'GCC_SYMBOLS_PRIVATE_EXTERN': 'YES',      # -fvisibility=hidden
+          'GCC_THREADSAFE_STATICS': 'NO',           # -fno-threadsafe-statics
+          'GCC_TREAT_WARNINGS_AS_ERRORS': 'YES',    # -Werror
+          'GCC_VERSION': '4.2',
+          'GCC_WARN_ABOUT_MISSING_NEWLINE': 'YES',  # -Wnewline-eof
+          'MACOSX_DEPLOYMENT_TARGET': '10.4',       # -mmacosx-version-min=10.4
+          'PREBINDING': 'NO',                       # No -Wl,-prebind
+          'USE_HEADERMAP': 'NO',
+          'OTHER_CFLAGS': [
+            '-fno-strict-aliasing',
+          ],
+          'WARNING_CFLAGS': [
+            '-Wall',
+            '-Wendif-labels',
+            '-W',
+            '-Wno-unused-parameter',
+            '-Wnon-virtual-dtor',
+          ],
+        },
+        'target_conditions': [
+          ['_type!="static_library"', {
+            'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
+          }],
+        ],  # target_conditions
+      },  # target_defaults
+    }],  # OS=="mac"
+  ],
+}
diff --git a/build/v8-features.gypi b/build/v8-features.gypi
deleted file mode 100644
index 4037452..0000000
--- a/build/v8-features.gypi
+++ /dev/null
@@ -1,125 +0,0 @@
-# Copyright 2011 the V8 project authors. All rights reserved.
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are
-# met:
-#
-#     * Redistributions of source code must retain the above copyright
-#       notice, this list of conditions and the following disclaimer.
-#     * Redistributions in binary form must reproduce the above
-#       copyright notice, this list of conditions and the following
-#       disclaimer in the documentation and/or other materials provided
-#       with the distribution.
-#     * Neither the name of Google Inc. nor the names of its
-#       contributors may be used to endorse or promote products derived
-#       from this software without specific prior written permission.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-# TODO(sgjesse): This is currently copied from v8.gyp, should probably
-# be refactored.
-{
-  'variables': {
-    'use_system_v8%': 0,
-    'msvs_use_common_release': 0,
-    'gcc_version%': 'unknown',
-    'v8_compress_startup_data%': 'off',
-    'v8_target_arch%': '<(target_arch)',
-
-    # Setting 'v8_can_use_unaligned_accesses' to 'true' will allow the code
-    # generated by V8 to do unaligned memory access, and setting it to 'false'
-    # will ensure that the generated code will always do aligned memory
-    # accesses. The default value of 'default' will try to determine the correct
-    # setting. Note that for Intel architectures (ia32 and x64) unaligned memory
-    # access is allowed for all CPUs.
-    'v8_can_use_unaligned_accesses%': 'default',
-
-    # Setting 'v8_can_use_vfp_instructions' to 'true' will enable use of ARM VFP
-    # instructions in the V8 generated code. VFP instructions will be enabled
-    # both for the snapshot and for the ARM target. Leaving the default value
-    # of 'false' will avoid VFP instructions in the snapshot and use CPU feature
-    # probing when running on the target.
-    'v8_can_use_vfp_instructions%': 'false',
-
-    # Setting v8_use_arm_eabi_hardfloat to true will turn on V8 support for ARM
-    # EABI calling convention where double arguments are passed in VFP
-    # registers. Note that the GCC flag '-mfloat-abi=hard' should be used as
-    # well when compiling for the ARM target.
-    'v8_use_arm_eabi_hardfloat%': 'false',
-
-    'v8_use_snapshot%': 'true',
-    'host_os%': '<(OS)',
-    'v8_use_liveobjectlist%': 'false',
-  },
-  'target_defaults': {
-    'conditions': [
-      ['OS!="mac"', {
-        'conditions': [
-          ['v8_target_arch=="arm"', {
-            'defines': [
-              'V8_TARGET_ARCH_ARM',
-            ],
-            'conditions': [
-              [ 'v8_can_use_unaligned_accesses=="true"', {
-                'defines': [
-                  'CAN_USE_UNALIGNED_ACCESSES=1',
-                ],
-              }],
-              [ 'v8_can_use_unaligned_accesses=="false"', {
-                'defines': [
-                  'CAN_USE_UNALIGNED_ACCESSES=0',
-                ],
-              }],
-              [ 'v8_can_use_vfp_instructions=="true"', {
-                'defines': [
-                  'CAN_USE_VFP_INSTRUCTIONS',
-                ],
-              }],
-              [ 'v8_use_arm_eabi_hardfloat=="true"', {
-                'defines': [
-                  'USE_EABI_HARDFLOAT=1',
-                  'CAN_USE_VFP_INSTRUCTIONS',
-                ],
-              }],
-            ],
-          }],
-          ['v8_target_arch=="ia32"', {
-            'defines': [
-              'V8_TARGET_ARCH_IA32',
-            ],
-          }],
-          ['v8_target_arch=="mips"', {
-            'defines': [
-              'V8_TARGET_ARCH_MIPS',
-            ],
-          }],
-          ['v8_target_arch=="x64"', {
-            'defines': [
-              'V8_TARGET_ARCH_X64',
-            ],
-          }],
-        ],
-      }],
-    ],
-    'configurations': {
-      'Debug': {
-        'defines': [
-          'DEBUG',
-          '_DEBUG',
-          'ENABLE_DISASSEMBLER',
-          'V8_ENABLE_CHECKS',
-          'OBJECT_PRINT',
-        ],
-      }
-    }
-  }
-}
diff --git a/include/v8-debug.h b/include/v8-debug.h
old mode 100755
new mode 100644
diff --git a/include/v8-profiler.h b/include/v8-profiler.h
index 4febcb9..f67646f 100644
--- a/include/v8-profiler.h
+++ b/include/v8-profiler.h
@@ -307,6 +307,12 @@
    * path from the snapshot root to the current node.
    */
   const HeapGraphNode* GetDominatorNode() const;
+
+  /**
+   * Finds and returns a value from the heap corresponding to this node,
+   * if the value is still reachable.
+   */
+  Handle<Value> GetHeapValue() const;
 };
 
 
diff --git a/include/v8.h b/include/v8.h
index f4f81e4..5a78160 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -171,12 +171,12 @@
   /**
    * Creates an empty handle.
    */
-  inline Handle();
+  inline Handle() : val_(0) {}
 
   /**
    * Creates a new handle for the specified value.
    */
-  inline explicit Handle(T* val) : val_(val) { }
+  inline explicit Handle(T* val) : val_(val) {}
 
   /**
    * Creates a handle for the contents of the specified handle.  This
@@ -203,14 +203,14 @@
    */
   inline bool IsEmpty() const { return val_ == 0; }
 
-  inline T* operator->() const { return val_; }
-
-  inline T* operator*() const { return val_; }
-
   /**
    * Sets the handle to be empty. IsEmpty() will then return true.
    */
-  inline void Clear() { this->val_ = 0; }
+  inline void Clear() { val_ = 0; }
+
+  inline T* operator->() const { return val_; }
+
+  inline T* operator*() const { return val_; }
 
   /**
    * Checks whether two handles are the same.
@@ -1039,29 +1039,30 @@
    * \param length The number of characters to copy from the string.  For
    *    WriteUtf8 the number of bytes in the buffer.
    * \param nchars_ref The number of characters written, can be NULL.
-   * \param hints Various hints that might affect performance of this or
+   * \param options Various options that might affect performance of this or
    *    subsequent operations.
    * \return The number of characters copied to the buffer excluding the null
    *    terminator.  For WriteUtf8: The number of bytes copied to the buffer
-   *    including the null terminator.
+   *    including the null terminator (if written).
    */
-  enum WriteHints {
-    NO_HINTS = 0,
-    HINT_MANY_WRITES_EXPECTED = 1
+  enum WriteOptions {
+    NO_OPTIONS = 0,
+    HINT_MANY_WRITES_EXPECTED = 1,
+    NO_NULL_TERMINATION = 2
   };
 
   V8EXPORT int Write(uint16_t* buffer,
                      int start = 0,
                      int length = -1,
-                     WriteHints hints = NO_HINTS) const;  // UTF-16
+                     int options = NO_OPTIONS) const;  // UTF-16
   V8EXPORT int WriteAscii(char* buffer,
                           int start = 0,
                           int length = -1,
-                          WriteHints hints = NO_HINTS) const;  // ASCII
+                          int options = NO_OPTIONS) const;  // ASCII
   V8EXPORT int WriteUtf8(char* buffer,
                          int length = -1,
                          int* nchars_ref = NULL,
-                         WriteHints hints = NO_HINTS) const;  // UTF-8
+                         int options = NO_OPTIONS) const;  // UTF-8
 
   /**
    * A zero length string.
@@ -1335,7 +1336,7 @@
   static inline Number* Cast(v8::Value* obj);
  private:
   V8EXPORT Number();
-  static void CheckCast(v8::Value* obj);
+  V8EXPORT static void CheckCast(v8::Value* obj);
 };
 
 
@@ -1709,7 +1710,7 @@
   static inline Array* Cast(Value* obj);
  private:
   V8EXPORT Array();
-  static void CheckCast(Value* obj);
+  V8EXPORT static void CheckCast(Value* obj);
 };
 
 
@@ -2231,11 +2232,10 @@
   void SetHiddenPrototype(bool value);
 
   /**
-   * Sets the property attributes of the 'prototype' property of functions
-   * created from this FunctionTemplate. Can be any combination of ReadOnly,
-   * DontEnum and DontDelete.
+   * Sets the ReadOnly flag in the attributes of the 'prototype' property
+   * of functions created from this FunctionTemplate to true.
    */
-  void SetPrototypeAttributes(int attributes);
+  void ReadOnlyPrototype();
 
   /**
    * Returns true if the given object is an instance of this function
@@ -3607,7 +3607,7 @@
   /**
    * Returns whether v8::Locker is being used by this V8 instance.
    */
-  static bool IsActive() { return active_; }
+  static bool IsActive();
 
  private:
   bool has_lock_;
@@ -3828,10 +3828,6 @@
 
 
 template <class T>
-Handle<T>::Handle() : val_(0) { }
-
-
-template <class T>
 Local<T>::Local() : Handle<T>() { }
 
 
diff --git a/preparser/preparser.gyp b/preparser/preparser.gyp
new file mode 100644
index 0000000..0b03382
--- /dev/null
+++ b/preparser/preparser.gyp
@@ -0,0 +1,42 @@
+# Copyright 2011 the V8 project authors. All rights reserved.
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+#     * Neither the name of Google Inc. nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+{
+  'includes': ['../build/common.gypi'],
+  'targets': [
+    {
+      'target_name': 'preparser',
+      'type': 'executable',
+      'dependencies': [
+        '../tools/gyp/v8.gyp:preparser_lib',
+      ],
+      'sources': [
+        'preparser-process.cc',
+      ],
+    },
+  ],
+}
diff --git a/samples/samples.gyp b/samples/samples.gyp
index f383ee2..55b2a98 100644
--- a/samples/samples.gyp
+++ b/samples/samples.gyp
@@ -1,4 +1,4 @@
-# Copyright 2010 the V8 project authors. All rights reserved.
+# Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
@@ -26,23 +26,25 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 {
+  'includes': ['../build/common.gypi'],
+  'target_defaults': {
+    'type': 'executable',
+    'dependencies': [
+      '../tools/gyp/v8.gyp:v8',
+    ],
+    'include_dirs': [
+      '../include',
+    ],
+  },
   'targets': [
     {
       'target_name': 'shell',
-      'type': 'executable',
-      'dependencies': [
-        '../tools/gyp/v8.gyp:v8',
-      ],
       'sources': [
         'shell.cc',
       ],
     },
     {
       'target_name': 'process',
-      'type': 'executable',
-      'dependencies': [
-        '../tools/gyp/v8.gyp:v8',
-      ],
       'sources': [
         'process.cc',
       ],
diff --git a/samples/shell.cc b/samples/shell.cc
index f37e731..8ed9d03 100644
--- a/samples/shell.cc
+++ b/samples/shell.cc
@@ -26,39 +26,28 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <v8.h>
-#include <v8-testing.h>
 #include <assert.h>
-#ifdef COMPRESS_STARTUP_DATA_BZ2
-#include <bzlib.h>
-#endif
 #include <fcntl.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 
-// When building with V8 in a shared library we cannot use functions which
-// is not explicitly a part of the public V8 API. This extensive use of
-// #ifndef USING_V8_SHARED/#endif is a hack until we can resolve whether to
-// still use the shell sample for testing or change to use the developer
-// shell d8 TODO(1272).
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-#include "../src/v8.h"
-#endif  // USING_V8_SHARED
-
-#if !defined(_WIN32) && !defined(_WIN64)
-#include <unistd.h>  // NOLINT
+#ifdef COMPRESS_STARTUP_DATA_BZ2
+#error Using compressed startup data is not supported for this sample
 #endif
 
-static void ExitShell(int exit_code) {
-  // Use _exit instead of exit to avoid races between isolate
-  // threads and static destructors.
-  fflush(stdout);
-  fflush(stderr);
-  _exit(exit_code);
-}
+/**
+ * This sample program shows how to implement a simple javascript shell
+ * based on V8.  This includes initializing V8 with command line options,
+ * creating global functions, compiling and executing strings.
+ *
+ * For a more sophisticated shell, consider using the debug shell D8.
+ */
+
 
 v8::Persistent<v8::Context> CreateShellContext();
 void RunShell(v8::Handle<v8::Context> context);
+int RunMain(int argc, char* argv[]);
 bool ExecuteString(v8::Handle<v8::String> source,
                    v8::Handle<v8::Value> name,
                    bool print_result,
@@ -68,305 +57,28 @@
 v8::Handle<v8::Value> Load(const v8::Arguments& args);
 v8::Handle<v8::Value> Quit(const v8::Arguments& args);
 v8::Handle<v8::Value> Version(const v8::Arguments& args);
-v8::Handle<v8::Value> Int8Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Uint8Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Int16Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Uint16Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Int32Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Uint32Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Float32Array(const v8::Arguments& args);
-v8::Handle<v8::Value> Float64Array(const v8::Arguments& args);
-v8::Handle<v8::Value> PixelArray(const v8::Arguments& args);
 v8::Handle<v8::String> ReadFile(const char* name);
 void ReportException(v8::TryCatch* handler);
 
 
-static bool last_run = true;
-
-class SourceGroup {
- public:
-  SourceGroup() :
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-                  next_semaphore_(v8::internal::OS::CreateSemaphore(0)),
-                  done_semaphore_(v8::internal::OS::CreateSemaphore(0)),
-                  thread_(NULL),
-#endif  // USING_V8_SHARED
-                  argv_(NULL),
-                  begin_offset_(0),
-                  end_offset_(0) { }
-
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-  ~SourceGroup() {
-    delete next_semaphore_;
-    delete done_semaphore_;
-  }
-#endif  // USING_V8_SHARED
-
-  void Begin(char** argv, int offset) {
-    argv_ = const_cast<const char**>(argv);
-    begin_offset_ = offset;
-  }
-
-  void End(int offset) { end_offset_ = offset; }
-
-  void Execute() {
-    for (int i = begin_offset_; i < end_offset_; ++i) {
-      const char* arg = argv_[i];
-      if (strcmp(arg, "-e") == 0 && i + 1 < end_offset_) {
-        // Execute argument given to -e option directly.
-        v8::HandleScope handle_scope;
-        v8::Handle<v8::String> file_name = v8::String::New("unnamed");
-        v8::Handle<v8::String> source = v8::String::New(argv_[i + 1]);
-        if (!ExecuteString(source, file_name, false, true)) {
-          ExitShell(1);
-          return;
-        }
-        ++i;
-      } else if (arg[0] == '-') {
-        // Ignore other options. They have been parsed already.
-      } else {
-        // Use all other arguments as names of files to load and run.
-        v8::HandleScope handle_scope;
-        v8::Handle<v8::String> file_name = v8::String::New(arg);
-        v8::Handle<v8::String> source = ReadFile(arg);
-        if (source.IsEmpty()) {
-          printf("Error reading '%s'\n", arg);
-          continue;
-        }
-        if (!ExecuteString(source, file_name, false, true)) {
-          ExitShell(1);
-          return;
-        }
-      }
-    }
-  }
-
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-  void StartExecuteInThread() {
-    if (thread_ == NULL) {
-      thread_ = new IsolateThread(this);
-      thread_->Start();
-    }
-    next_semaphore_->Signal();
-  }
-
-  void WaitForThread() {
-    if (thread_ == NULL) return;
-    if (last_run) {
-      thread_->Join();
-      thread_ = NULL;
-    } else {
-      done_semaphore_->Wait();
-    }
-  }
-#endif  // USING_V8_SHARED
-
- private:
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-  static v8::internal::Thread::Options GetThreadOptions() {
-    v8::internal::Thread::Options options;
-    options.name = "IsolateThread";
-    // On some systems (OSX 10.6) the stack size default is 0.5Mb or less
-    // which is not enough to parse the big literal expressions used in tests.
-    // The stack size should be at least StackGuard::kLimitSize + some
-    // OS-specific padding for thread startup code.
-    options.stack_size = 2 << 20;  // 2 Mb seems to be enough
-    return options;
-  }
-
-  class IsolateThread : public v8::internal::Thread {
-   public:
-    explicit IsolateThread(SourceGroup* group)
-        : v8::internal::Thread(GetThreadOptions()), group_(group) {}
-
-    virtual void Run() {
-      group_->ExecuteInThread();
-    }
-
-   private:
-    SourceGroup* group_;
-  };
-
-  void ExecuteInThread() {
-    v8::Isolate* isolate = v8::Isolate::New();
-    do {
-      if (next_semaphore_ != NULL) next_semaphore_->Wait();
-      {
-        v8::Isolate::Scope iscope(isolate);
-        v8::HandleScope scope;
-        v8::Persistent<v8::Context> context = CreateShellContext();
-        {
-          v8::Context::Scope cscope(context);
-          Execute();
-        }
-        context.Dispose();
-      }
-      if (done_semaphore_ != NULL) done_semaphore_->Signal();
-    } while (!last_run);
-    isolate->Dispose();
-  }
-
-  v8::internal::Semaphore* next_semaphore_;
-  v8::internal::Semaphore* done_semaphore_;
-  v8::internal::Thread* thread_;
-#endif  // USING_V8_SHARED
-
-  const char** argv_;
-  int begin_offset_;
-  int end_offset_;
-};
+static bool run_shell;
 
 
-static SourceGroup* isolate_sources = NULL;
-
-
-#ifdef COMPRESS_STARTUP_DATA_BZ2
-class BZip2Decompressor : public v8::StartupDataDecompressor {
- public:
-  virtual ~BZip2Decompressor() { }
-
- protected:
-  virtual int DecompressData(char* raw_data,
-                             int* raw_data_size,
-                             const char* compressed_data,
-                             int compressed_data_size) {
-    ASSERT_EQ(v8::StartupData::kBZip2,
-              v8::V8::GetCompressedStartupDataAlgorithm());
-    unsigned int decompressed_size = *raw_data_size;
-    int result =
-        BZ2_bzBuffToBuffDecompress(raw_data,
-                                   &decompressed_size,
-                                   const_cast<char*>(compressed_data),
-                                   compressed_data_size,
-                                   0, 1);
-    if (result == BZ_OK) {
-      *raw_data_size = decompressed_size;
-    }
-    return result;
-  }
-};
-#endif
-
-
-int RunMain(int argc, char* argv[]) {
+int main(int argc, char* argv[]) {
   v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
+  run_shell = (argc == 1);
   v8::HandleScope handle_scope;
   v8::Persistent<v8::Context> context = CreateShellContext();
-  // Enter the newly created execution environment.
-  context->Enter();
   if (context.IsEmpty()) {
     printf("Error creating context\n");
     return 1;
   }
-
-  bool run_shell = (argc == 1);
-  int num_isolates = 1;
-  for (int i = 1; i < argc; i++) {
-    if (strcmp(argv[i], "--isolate") == 0) {
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-      ++num_isolates;
-#else  // USING_V8_SHARED
-      printf("Error: --isolate not supported when linked with shared "
-             "library\n");
-      ExitShell(1);
-#endif  // USING_V8_SHARED
-    }
-  }
-  if (isolate_sources == NULL) {
-    isolate_sources = new SourceGroup[num_isolates];
-    SourceGroup* current = isolate_sources;
-    current->Begin(argv, 1);
-    for (int i = 1; i < argc; i++) {
-      const char* str = argv[i];
-      if (strcmp(str, "--isolate") == 0) {
-        current->End(i);
-        current++;
-        current->Begin(argv, i + 1);
-      } else if (strcmp(str, "--shell") == 0) {
-        run_shell = true;
-      } else if (strcmp(str, "-f") == 0) {
-        // Ignore any -f flags for compatibility with the other stand-
-        // alone JavaScript engines.
-        continue;
-      } else if (strncmp(str, "--", 2) == 0) {
-        printf("Warning: unknown flag %s.\nTry --help for options\n", str);
-      }
-    }
-    current->End(argc);
-  }
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-  for (int i = 1; i < num_isolates; ++i) {
-    isolate_sources[i].StartExecuteInThread();
-  }
-#endif  // USING_V8_SHARED
-  isolate_sources[0].Execute();
+  context->Enter();
+  int result = RunMain(argc, argv);
   if (run_shell) RunShell(context);
-#if !(defined(USING_V8_SHARED) || defined(V8_SHARED))
-  for (int i = 1; i < num_isolates; ++i) {
-    isolate_sources[i].WaitForThread();
-  }
-#endif  // USING_V8_SHARED
-  if (last_run) {
-    delete[] isolate_sources;
-    isolate_sources = NULL;
-  }
   context->Exit();
   context.Dispose();
-  return 0;
-}
-
-
-int main(int argc, char* argv[]) {
-  // Figure out if we're requested to stress the optimization
-  // infrastructure by running tests multiple times and forcing
-  // optimization in the last run.
-  bool FLAG_stress_opt = false;
-  bool FLAG_stress_deopt = false;
-  for (int i = 0; i < argc; i++) {
-    if (strcmp(argv[i], "--stress-opt") == 0) {
-      FLAG_stress_opt = true;
-      argv[i] = NULL;
-    } else if (strcmp(argv[i], "--stress-deopt") == 0) {
-      FLAG_stress_deopt = true;
-      argv[i] = NULL;
-    } else if (strcmp(argv[i], "--noalways-opt") == 0) {
-      // No support for stressing if we can't use --always-opt.
-      FLAG_stress_opt = false;
-      FLAG_stress_deopt = false;
-      break;
-    }
-  }
-
-#ifdef COMPRESS_STARTUP_DATA_BZ2
-  BZip2Decompressor startup_data_decompressor;
-  int bz2_result = startup_data_decompressor.Decompress();
-  if (bz2_result != BZ_OK) {
-    fprintf(stderr, "bzip error code: %d\n", bz2_result);
-    exit(1);
-  }
-#endif
-
-  v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
-  int result = 0;
-  if (FLAG_stress_opt || FLAG_stress_deopt) {
-    v8::Testing::SetStressRunType(FLAG_stress_opt
-                                  ? v8::Testing::kStressTypeOpt
-                                  : v8::Testing::kStressTypeDeopt);
-    int stress_runs = v8::Testing::GetStressRuns();
-    for (int i = 0; i < stress_runs && result == 0; i++) {
-      printf("============ Stress %d/%d ============\n",
-             i + 1, stress_runs);
-      v8::Testing::PrepareStressRun(i);
-      last_run = (i == stress_runs - 1);
-      result = RunMain(argc, argv);
-    }
-    printf("======== Full Deoptimization =======\n");
-    v8::Testing::DeoptimizeAll();
-  } else {
-    result = RunMain(argc, argv);
-  }
   v8::V8::Dispose();
-
   return result;
 }
 
@@ -393,26 +105,6 @@
   // Bind the 'version' function
   global->Set(v8::String::New("version"), v8::FunctionTemplate::New(Version));
 
-  // Bind the handlers for external arrays.
-  global->Set(v8::String::New("Int8Array"),
-              v8::FunctionTemplate::New(Int8Array));
-  global->Set(v8::String::New("Uint8Array"),
-              v8::FunctionTemplate::New(Uint8Array));
-  global->Set(v8::String::New("Int16Array"),
-              v8::FunctionTemplate::New(Int16Array));
-  global->Set(v8::String::New("Uint16Array"),
-              v8::FunctionTemplate::New(Uint16Array));
-  global->Set(v8::String::New("Int32Array"),
-              v8::FunctionTemplate::New(Int32Array));
-  global->Set(v8::String::New("Uint32Array"),
-              v8::FunctionTemplate::New(Uint32Array));
-  global->Set(v8::String::New("Float32Array"),
-              v8::FunctionTemplate::New(Float32Array));
-  global->Set(v8::String::New("Float64Array"),
-              v8::FunctionTemplate::New(Float64Array));
-  global->Set(v8::String::New("PixelArray"),
-              v8::FunctionTemplate::New(PixelArray));
-
   return v8::Context::New(NULL, global);
 }
 
@@ -486,7 +178,9 @@
   // If not arguments are given args[0] will yield undefined which
   // converts to the integer value 0.
   int exit_code = args[0]->Int32Value();
-  ExitShell(exit_code);
+  fflush(stdout);
+  fflush(stderr);
+  exit(exit_code);
   return v8::Undefined();
 }
 
@@ -496,113 +190,6 @@
 }
 
 
-void ExternalArrayWeakCallback(v8::Persistent<v8::Value> object, void* data) {
-  free(data);
-  object.Dispose();
-}
-
-
-v8::Handle<v8::Value> CreateExternalArray(const v8::Arguments& args,
-                                          v8::ExternalArrayType type,
-                                          size_t element_size) {
-  assert(element_size == 1 ||
-         element_size == 2 ||
-         element_size == 4 ||
-         element_size == 8);
-  if (args.Length() != 1) {
-    return v8::ThrowException(
-        v8::String::New("Array constructor needs one parameter."));
-  }
-  static const int kMaxLength = 0x3fffffff;
-  size_t length = 0;
-  if (args[0]->IsUint32()) {
-    length = args[0]->Uint32Value();
-  } else if (args[0]->IsNumber()) {
-    double raw_length = args[0]->NumberValue();
-    if (raw_length < 0) {
-      return v8::ThrowException(
-          v8::String::New("Array length must not be negative."));
-    }
-    if (raw_length > kMaxLength) {
-      return v8::ThrowException(
-          v8::String::New("Array length exceeds maximum length."));
-    }
-    length = static_cast<size_t>(raw_length);
-  } else {
-    return v8::ThrowException(
-        v8::String::New("Array length must be a number."));
-  }
-  if (length > static_cast<size_t>(kMaxLength)) {
-    return v8::ThrowException(
-        v8::String::New("Array length exceeds maximum length."));
-  }
-  void* data = calloc(length, element_size);
-  if (data == NULL) {
-    return v8::ThrowException(v8::String::New("Memory allocation failed."));
-  }
-  v8::Handle<v8::Object> array = v8::Object::New();
-  v8::Persistent<v8::Object> persistent_array =
-      v8::Persistent<v8::Object>::New(array);
-  persistent_array.MakeWeak(data, ExternalArrayWeakCallback);
-  persistent_array.MarkIndependent();
-  array->SetIndexedPropertiesToExternalArrayData(data, type, length);
-  array->Set(v8::String::New("length"), v8::Int32::New(length),
-             v8::ReadOnly);
-  array->Set(v8::String::New("BYTES_PER_ELEMENT"),
-             v8::Int32::New(element_size));
-  return array;
-}
-
-
-v8::Handle<v8::Value> Int8Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalByteArray, sizeof(int8_t));
-}
-
-
-v8::Handle<v8::Value> Uint8Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalUnsignedByteArray,
-                             sizeof(uint8_t));
-}
-
-
-v8::Handle<v8::Value> Int16Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalShortArray, sizeof(int16_t));
-}
-
-
-v8::Handle<v8::Value> Uint16Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalUnsignedShortArray,
-                             sizeof(uint16_t));
-}
-
-v8::Handle<v8::Value> Int32Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalIntArray, sizeof(int32_t));
-}
-
-
-v8::Handle<v8::Value> Uint32Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalUnsignedIntArray,
-                             sizeof(uint32_t));
-}
-
-
-v8::Handle<v8::Value> Float32Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalFloatArray,
-                             sizeof(float));  // NOLINT
-}
-
-
-v8::Handle<v8::Value> Float64Array(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalDoubleArray,
-                             sizeof(double));  // NOLINT
-}
-
-
-v8::Handle<v8::Value> PixelArray(const v8::Arguments& args) {
-  return CreateExternalArray(args, v8::kExternalPixelArray, sizeof(uint8_t));
-}
-
-
 // Reads a file into a v8 string.
 v8::Handle<v8::String> ReadFile(const char* name) {
   FILE* file = fopen(name, "rb");
@@ -625,9 +212,41 @@
 }
 
 
+// Process remaining command line arguments and execute files
+int RunMain(int argc, char* argv[]) {
+  for (int i = 1; i < argc; i++) {
+    const char* str = argv[i];
+    if (strcmp(str, "--shell") == 0) {
+      run_shell = true;
+    } else if (strcmp(str, "-f") == 0) {
+      // Ignore any -f flags for compatibility with the other stand-
+      // alone JavaScript engines.
+      continue;
+    } else if (strncmp(str, "--", 2) == 0) {
+      printf("Warning: unknown flag %s.\nTry --help for options\n", str);
+    } else if (strcmp(str, "-e") == 0 && i + 1 < argc) {
+      // Execute argument given to -e option directly.
+      v8::Handle<v8::String> file_name = v8::String::New("unnamed");
+      v8::Handle<v8::String> source = v8::String::New(argv[++i]);
+      if (!ExecuteString(source, file_name, false, true)) return 1;
+    } else {
+      // Use all other arguments as names of files to load and run.
+      v8::Handle<v8::String> file_name = v8::String::New(str);
+      v8::Handle<v8::String> source = ReadFile(str);
+      if (source.IsEmpty()) {
+        printf("Error reading '%s'\n", str);
+        continue;
+      }
+      if (!ExecuteString(source, file_name, false, true)) return 1;
+    }
+  }
+  return 0;
+}
+
+
 // The read-eval-execute loop of the shell.
 void RunShell(v8::Handle<v8::Context> context) {
-  printf("V8 version %s\n", v8::V8::GetVersion());
+  printf("V8 version %s [sample shell]\n", v8::V8::GetVersion());
   static const int kBufferSize = 256;
   // Enter the execution environment before evaluating any code.
   v8::Context::Scope context_scope(context);
diff --git a/src/SConscript b/src/SConscript
old mode 100755
new mode 100644
index b45a567..453a7c6
--- a/src/SConscript
+++ b/src/SConscript
@@ -32,6 +32,7 @@
 import js2c
 Import('context')
 Import('tools')
+Import('d8_env')
 
 
 SOURCES = {
@@ -65,6 +66,7 @@
     disassembler.cc
     diy-fp.cc
     dtoa.cc
+    elements.cc
     execution.cc
     factory.cc
     flags.cc
@@ -307,6 +309,7 @@
 
 EXPERIMENTAL_LIBRARY_FILES = '''
 proxy.js
+weakmap.js
 '''.split()
 
 
@@ -338,7 +341,7 @@
   else:
     d8_files = context.GetRelevantSources(D8_FULL_FILES)
     d8_objs = [d8_js_obj]
-  d8_objs.append(context.ConfigureObject(env, [d8_files]))
+  d8_objs.append(context.ConfigureObject(d8_env, [d8_files]))
 
   # Combine the JavaScript library files into a single C++ file and
   # compile it.
diff --git a/src/api.cc b/src/api.cc
index b0e9775..5bda725 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -35,6 +35,7 @@
 #include "debug.h"
 #include "deoptimizer.h"
 #include "execution.h"
+#include "flags.h"
 #include "global-handles.h"
 #include "heap-profiler.h"
 #include "messages.h"
@@ -84,7 +85,7 @@
     if (has_pending_exception) {                                               \
       if (handle_scope_implementer->CallDepthIsZero() &&                       \
           (isolate)->is_out_of_memory()) {                                     \
-        if (!handle_scope_implementer->ignore_out_of_memory())                 \
+        if (!(isolate)->ignore_out_of_memory())                                \
           i::V8::FatalProcessOutOfMemory(NULL);                                \
       }                                                                        \
       bool call_depth_is_zero = handle_scope_implementer->CallDepthIsZero();   \
@@ -877,7 +878,6 @@
       i::Handle<i::FunctionTemplateInfo> info) {
   info->set_tag(i::Smi::FromInt(Consts::FUNCTION_TEMPLATE));
   info->set_flag(0);
-  info->set_prototype_attributes(i::Smi::FromInt(v8::None));
 }
 
 
@@ -1100,14 +1100,13 @@
 }
 
 
-void FunctionTemplate::SetPrototypeAttributes(int attributes) {
+void FunctionTemplate::ReadOnlyPrototype() {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   if (IsDeadCheck(isolate, "v8::FunctionTemplate::SetPrototypeAttributes()")) {
     return;
   }
   ENTER_V8(isolate);
-  Utils::OpenHandle(this)->set_prototype_attributes(
-      i::Smi::FromInt(attributes));
+  Utils::OpenHandle(this)->set_read_only_prototype(true);
 }
 
 
@@ -1407,7 +1406,7 @@
 ScriptData* ScriptData::PreCompile(const char* input, int length) {
   i::Utf8ToUC16CharacterStream stream(
       reinterpret_cast<const unsigned char*>(input), length);
-  return i::ParserApi::PreParse(&stream, NULL);
+  return i::ParserApi::PreParse(&stream, NULL, i::FLAG_harmony_block_scoping);
 }
 
 
@@ -1416,10 +1415,10 @@
   if (str->IsExternalTwoByteString()) {
     i::ExternalTwoByteStringUC16CharacterStream stream(
       i::Handle<i::ExternalTwoByteString>::cast(str), 0, str->length());
-    return i::ParserApi::PreParse(&stream, NULL);
+    return i::ParserApi::PreParse(&stream, NULL, i::FLAG_harmony_block_scoping);
   } else {
     i::GenericStringUC16CharacterStream stream(str, 0, str->length());
-    return i::ParserApi::PreParse(&stream, NULL);
+    return i::ParserApi::PreParse(&stream, NULL, i::FLAG_harmony_block_scoping);
   }
 }
 
@@ -3165,10 +3164,9 @@
   i::Object* constructor = object->map()->constructor();
   i::JSFunction* function;
   if (!constructor->IsJSFunction()) {
-    // API functions have null as a constructor,
+    // Functions have null as a constructor,
     // but any JSFunction knows its context immediately.
-    ASSERT(object->IsJSFunction() &&
-           i::JSFunction::cast(object)->shared()->IsApiFunction());
+    ASSERT(object->IsJSFunction());
     function = i::JSFunction::cast(object);
   } else {
     function = i::JSFunction::cast(constructor);
@@ -3194,39 +3192,7 @@
   ENTER_V8(isolate);
   i::HandleScope scope(isolate);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
-  i::Handle<i::Object> hidden_props_obj(i::GetHiddenProperties(self, true));
-  if (!hidden_props_obj->IsJSObject()) {
-    // We failed to create hidden properties.  That's a detached
-    // global proxy.
-    ASSERT(hidden_props_obj->IsUndefined());
-    return 0;
-  }
-  i::Handle<i::JSObject> hidden_props =
-      i::Handle<i::JSObject>::cast(hidden_props_obj);
-  i::Handle<i::String> hash_symbol = isolate->factory()->identity_hash_symbol();
-  if (hidden_props->HasLocalProperty(*hash_symbol)) {
-    i::Handle<i::Object> hash = i::GetProperty(hidden_props, hash_symbol);
-    CHECK(!hash.is_null());
-    CHECK(hash->IsSmi());
-    return i::Smi::cast(*hash)->value();
-  }
-
-  int hash_value;
-  int attempts = 0;
-  do {
-    // Generate a random 32-bit hash value but limit range to fit
-    // within a smi.
-    hash_value = i::V8::Random(self->GetIsolate()) & i::Smi::kMaxValue;
-    attempts++;
-  } while (hash_value == 0 && attempts < 30);
-  hash_value = hash_value != 0 ? hash_value : 1;  // never return 0
-  CHECK(!i::SetLocalPropertyIgnoreAttributes(
-          hidden_props,
-          hash_symbol,
-          i::Handle<i::Object>(i::Smi::FromInt(hash_value)),
-          static_cast<PropertyAttributes>(None)).is_null());
-
-  return hash_value;
+  return i::GetIdentityHash(self);
 }
 
 
@@ -3237,7 +3203,9 @@
   ENTER_V8(isolate);
   i::HandleScope scope(isolate);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
-  i::Handle<i::Object> hidden_props(i::GetHiddenProperties(self, true));
+  i::Handle<i::Object> hidden_props(i::GetHiddenProperties(
+      self,
+      i::JSObject::ALLOW_CREATION));
   i::Handle<i::Object> key_obj = Utils::OpenHandle(*key);
   i::Handle<i::Object> value_obj = Utils::OpenHandle(*value);
   EXCEPTION_PREAMBLE(isolate);
@@ -3259,7 +3227,9 @@
              return Local<v8::Value>());
   ENTER_V8(isolate);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
-  i::Handle<i::Object> hidden_props(i::GetHiddenProperties(self, false));
+  i::Handle<i::Object> hidden_props(i::GetHiddenProperties(
+      self,
+      i::JSObject::OMIT_CREATION));
   if (hidden_props->IsUndefined()) {
     return v8::Local<v8::Value>();
   }
@@ -3281,7 +3251,9 @@
   ENTER_V8(isolate);
   i::HandleScope scope(isolate);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
-  i::Handle<i::Object> hidden_props(i::GetHiddenProperties(self, false));
+  i::Handle<i::Object> hidden_props(i::GetHiddenProperties(
+      self,
+      i::JSObject::OMIT_CREATION));
   if (hidden_props->IsUndefined()) {
     return true;
   }
@@ -3649,7 +3621,7 @@
 int String::WriteUtf8(char* buffer,
                       int capacity,
                       int* nchars_ref,
-                      WriteHints hints) const {
+                      int options) const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::WriteUtf8()")) return 0;
   LOG_API(isolate, "String::WriteUtf8");
@@ -3657,7 +3629,7 @@
   i::StringInputBuffer& write_input_buffer = *isolate->write_input_buffer();
   i::Handle<i::String> str = Utils::OpenHandle(this);
   isolate->string_tracker()->RecordWrite(str);
-  if (hints & HINT_MANY_WRITES_EXPECTED) {
+  if (options & HINT_MANY_WRITES_EXPECTED) {
     // Flatten the string for efficiency.  This applies whether we are
     // using StringInputBuffer or Get(i) to access the characters.
     str->TryFlatten();
@@ -3697,7 +3669,8 @@
     }
   }
   if (nchars_ref != NULL) *nchars_ref = nchars;
-  if (i == len && (capacity == -1 || pos < capacity))
+  if (!(options & NO_NULL_TERMINATION) &&
+      (i == len && (capacity == -1 || pos < capacity)))
     buffer[pos++] = '\0';
   return pos;
 }
@@ -3706,7 +3679,7 @@
 int String::WriteAscii(char* buffer,
                        int start,
                        int length,
-                       WriteHints hints) const {
+                       int options) const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::WriteAscii()")) return 0;
   LOG_API(isolate, "String::WriteAscii");
@@ -3715,7 +3688,7 @@
   ASSERT(start >= 0 && length >= -1);
   i::Handle<i::String> str = Utils::OpenHandle(this);
   isolate->string_tracker()->RecordWrite(str);
-  if (hints & HINT_MANY_WRITES_EXPECTED) {
+  if (options & HINT_MANY_WRITES_EXPECTED) {
     // Flatten the string for efficiency.  This applies whether we are
     // using StringInputBuffer or Get(i) to access the characters.
     str->TryFlatten();
@@ -3731,7 +3704,7 @@
     if (c == '\0') c = ' ';
     buffer[i] = c;
   }
-  if (length == -1 || i < length)
+  if (!(options & NO_NULL_TERMINATION) && (length == -1 || i < length))
     buffer[i] = '\0';
   return i;
 }
@@ -3740,7 +3713,7 @@
 int String::Write(uint16_t* buffer,
                   int start,
                   int length,
-                  WriteHints hints) const {
+                  int options) const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::Write()")) return 0;
   LOG_API(isolate, "String::Write");
@@ -3748,7 +3721,7 @@
   ASSERT(start >= 0 && length >= -1);
   i::Handle<i::String> str = Utils::OpenHandle(this);
   isolate->string_tracker()->RecordWrite(str);
-  if (hints & HINT_MANY_WRITES_EXPECTED) {
+  if (options & HINT_MANY_WRITES_EXPECTED) {
     // Flatten the string for efficiency.  This applies whether we are
     // using StringInputBuffer or Get(i) to access the characters.
     str->TryFlatten();
@@ -3758,7 +3731,8 @@
     end = str->length();
   if (end < 0) return 0;
   i::String::WriteToFlat(*str, buffer, start, end);
-  if (length == -1 || end - start < length) {
+  if (!(options & NO_NULL_TERMINATION) &&
+      (length == -1 || end - start < length)) {
     buffer[end - start] = '\0';
   }
   return end - start;
@@ -4146,7 +4120,7 @@
 
 v8::Local<v8::Context> Context::GetEntered() {
   i::Isolate* isolate = i::Isolate::Current();
-  if (IsDeadCheck(isolate, "v8::Context::GetEntered()")) {
+  if (!EnsureInitializedForIsolate(isolate, "v8::Context::GetEntered()")) {
     return Local<Context>();
   }
   i::Handle<i::Object> last =
@@ -4287,8 +4261,8 @@
 Local<Value> v8::External::Wrap(void* data) {
   i::Isolate* isolate = i::Isolate::Current();
   STATIC_ASSERT(sizeof(data) == sizeof(i::Address));
-  LOG_API(isolate, "External::Wrap");
   EnsureInitializedForIsolate(isolate, "v8::External::Wrap()");
+  LOG_API(isolate, "External::Wrap");
   ENTER_V8(isolate);
 
   v8::Local<v8::Value> result = CanBeEncodedAsSmi(data)
@@ -4332,8 +4306,8 @@
 Local<External> v8::External::New(void* data) {
   STATIC_ASSERT(sizeof(data) == sizeof(i::Address));
   i::Isolate* isolate = i::Isolate::Current();
-  LOG_API(isolate, "External::New");
   EnsureInitializedForIsolate(isolate, "v8::External::New()");
+  LOG_API(isolate, "External::New");
   ENTER_V8(isolate);
   return ExternalNewImpl(data);
 }
@@ -4825,8 +4799,7 @@
 
 
 void V8::IgnoreOutOfMemoryException() {
-  EnterIsolateIfNeeded()->handle_scope_implementer()->set_ignore_out_of_memory(
-      true);
+  EnterIsolateIfNeeded()->set_ignore_out_of_memory(true);
 }
 
 
@@ -5793,6 +5766,16 @@
 }
 
 
+v8::Handle<v8::Value> HeapGraphNode::GetHeapValue() const {
+  i::Isolate* isolate = i::Isolate::Current();
+  IsDeadCheck(isolate, "v8::HeapGraphNode::GetHeapValue");
+  i::Handle<i::HeapObject> object = ToInternal(this)->GetHeapObject();
+  return v8::Handle<Value>(!object.is_null() ?
+                           ToApi<Value>(object) : ToApi<Value>(
+                               isolate->factory()->undefined_value()));
+}
+
+
 static i::HeapSnapshot* ToInternal(const HeapSnapshot* snapshot) {
   return const_cast<i::HeapSnapshot*>(
       reinterpret_cast<const i::HeapSnapshot*>(snapshot));
diff --git a/src/api.h b/src/api.h
index 8d2e778..07723cb 100644
--- a/src/api.h
+++ b/src/api.h
@@ -404,9 +404,12 @@
         entered_contexts_(0),
         saved_contexts_(0),
         spare_(NULL),
-        ignore_out_of_memory_(false),
         call_depth_(0) { }
 
+  ~HandleScopeImplementer() {
+    DeleteArray(spare_);
+  }
+
   // Threading support for handle data.
   static int ArchiveSpacePerThread();
   char* RestoreThread(char* from);
@@ -437,10 +440,6 @@
   inline bool HasSavedContexts();
 
   inline List<internal::Object**>* blocks() { return &blocks_; }
-  inline bool ignore_out_of_memory() { return ignore_out_of_memory_; }
-  inline void set_ignore_out_of_memory(bool value) {
-    ignore_out_of_memory_ = value;
-  }
 
  private:
   void ResetAfterArchive() {
@@ -448,7 +447,6 @@
     entered_contexts_.Initialize(0);
     saved_contexts_.Initialize(0);
     spare_ = NULL;
-    ignore_out_of_memory_ = false;
     call_depth_ = 0;
   }
 
@@ -473,7 +471,6 @@
   // Used as a stack to keep track of saved contexts.
   List<Context*> saved_contexts_;
   Object** spare_;
-  bool ignore_out_of_memory_;
   int call_depth_;
   // This is only used for threading support.
   v8::ImplementationUtilities::HandleScopeData handle_scope_data_;
diff --git a/src/apinatives.js b/src/apinatives.js
index 193863f..e94da9f 100644
--- a/src/apinatives.js
+++ b/src/apinatives.js
@@ -49,7 +49,10 @@
       return InstantiateFunction(data, name);
     case kNewObjectTag:
       var Constructor = %GetTemplateField(data, kApiConstructorOffset);
-      var result = Constructor ? new (Instantiate(Constructor))() : {};
+      // Note: Do not directly use a function template as a condition, our
+      // internal ToBoolean doesn't handle that!
+      var result = typeof Constructor === 'undefined' ?
+          {} : new (Instantiate(Constructor))();
       ConfigureTemplateInstance(result, data);
       result = %ToFastProperties(result);
       return result;
@@ -73,18 +76,19 @@
       if (name) %FunctionSetName(fun, name);
       cache[serialNumber] = fun;
       var prototype = %GetTemplateField(data, kApiPrototypeTemplateOffset);
-      var attributes = %GetTemplateField(data, kApiPrototypeAttributesOffset);
-      if (attributes != NONE) {
-        %IgnoreAttributesAndSetProperty(
-            fun, "prototype",
-            prototype ? Instantiate(prototype) : {},
-            attributes);
-      } else {
-        fun.prototype = prototype ? Instantiate(prototype) : {};
+      var flags = %GetTemplateField(data, kApiFlagOffset);
+      // Note: Do not directly use an object template as a condition, our
+      // internal ToBoolean doesn't handle that!
+      fun.prototype = typeof prototype === 'undefined' ?
+          {} : Instantiate(prototype);
+      if (flags & (1 << kReadOnlyPrototypeBit)) {
+        %FunctionSetReadOnlyPrototype(fun);
       }
       %SetProperty(fun.prototype, "constructor", fun, DONT_ENUM);
       var parent = %GetTemplateField(data, kApiParentTemplateOffset);
-      if (parent) {
+      // Note: Do not directly use a function template as a condition, our
+      // internal ToBoolean doesn't handle that!
+      if (!(typeof parent === 'undefined')) {
         var parent_fun = Instantiate(parent);
         fun.prototype.__proto__ = parent_fun.prototype;
       }
diff --git a/src/arm/assembler-arm.cc b/src/arm/assembler-arm.cc
index 89df079..0ec3692 100644
--- a/src/arm/assembler-arm.cc
+++ b/src/arm/assembler-arm.cc
@@ -692,11 +692,11 @@
 void Assembler::next(Label* L) {
   ASSERT(L->is_linked());
   int link = target_at(L->pos());
-  if (link > 0) {
-    L->link_to(link);
-  } else {
-    ASSERT(link == kEndOfChain);
+  if (link == kEndOfChain) {
     L->Unuse();
+  } else {
+    ASSERT(link >= 0);
+    L->link_to(link);
   }
 }
 
diff --git a/src/arm/assembler-arm.h b/src/arm/assembler-arm.h
index 97d4226..9a58693 100644
--- a/src/arm/assembler-arm.h
+++ b/src/arm/assembler-arm.h
@@ -377,6 +377,9 @@
   // immediate
   INLINE(explicit Operand(int32_t immediate,
          RelocInfo::Mode rmode = RelocInfo::NONE));
+  INLINE(static Operand Zero()) {
+    return Operand(static_cast<int32_t>(0));
+  }
   INLINE(explicit Operand(const ExternalReference& f));
   explicit Operand(Handle<Object> handle);
   INLINE(explicit Operand(Smi* value));
diff --git a/src/arm/builtins-arm.cc b/src/arm/builtins-arm.cc
index 328102b..a35380c 100644
--- a/src/arm/builtins-arm.cc
+++ b/src/arm/builtins-arm.cc
@@ -138,7 +138,7 @@
   __ str(scratch1, FieldMemOperand(result, JSArray::kElementsOffset));
 
   // Clear the heap tag on the elements array.
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ sub(scratch1, scratch1, Operand(kHeapObjectTag));
 
   // Initialize the FixedArray and fill it with holes. FixedArray length is
@@ -207,7 +207,7 @@
   // Allocate the JSArray object together with space for a FixedArray with the
   // requested number of elements.
   __ bind(&not_empty);
-  ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
   __ mov(elements_array_end,
          Operand((JSArray::kSize + FixedArray::kHeaderSize) / kPointerSize));
   __ add(elements_array_end,
@@ -243,7 +243,7 @@
          FieldMemOperand(result, JSArray::kElementsOffset));
 
   // Clear the heap tag on the elements array.
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ sub(elements_array_storage,
          elements_array_storage,
          Operand(kHeapObjectTag));
@@ -255,7 +255,7 @@
   __ LoadRoot(scratch1, Heap::kFixedArrayMapRootIndex);
   ASSERT_EQ(0 * kPointerSize, FixedArray::kMapOffset);
   __ str(scratch1, MemOperand(elements_array_storage, kPointerSize, PostIndex));
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ tst(array_size, array_size);
   // Length of the FixedArray is the number of pre-allocated elements if
   // the actual JSArray has length 0 and the size of the JSArray for non-empty
@@ -272,7 +272,7 @@
   // result: JSObject
   // elements_array_storage: elements array element storage
   // array_size: smi-tagged size of elements array
-  ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
   __ add(elements_array_end,
          elements_array_storage,
          Operand(array_size, LSL, kPointerSizeLog2 - kSmiTagSize));
@@ -337,14 +337,14 @@
   __ bind(&argc_one_or_more);
   __ cmp(r0, Operand(1));
   __ b(ne, &argc_two_or_more);
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ ldr(r2, MemOperand(sp));  // Get the argument from the stack.
   __ and_(r3, r2, Operand(kIntptrSignBit | kSmiTagMask), SetCC);
   __ b(ne, call_generic_code);
 
   // Handle construction of an empty array of a certain size. Bail out if size
   // is too large to actually allocate an elements array.
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ cmp(r2, Operand(JSObject::kInitialMaxFastElementArray << kSmiTagSize));
   __ b(ge, call_generic_code);
 
@@ -571,7 +571,7 @@
   // Is it a String?
   __ ldr(r2, FieldMemOperand(r0, HeapObject::kMapOffset));
   __ ldrb(r3, FieldMemOperand(r2, Map::kInstanceTypeOffset));
-  ASSERT(kNotStringTag != 0);
+  STATIC_ASSERT(kNotStringTag != 0);
   __ tst(r3, Operand(kIsNotStringMask));
   __ b(ne, &convert_argument);
   __ mov(argument, r0);
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index eaad9f2..09d2c17 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -549,7 +549,7 @@
     // | s |   exp   |              mantissa               |
 
     // Check for zero.
-    __ cmp(int_scratch, Operand(0));
+    __ cmp(int_scratch, Operand::Zero());
     __ mov(dst2, int_scratch);
     __ mov(dst1, int_scratch);
     __ b(eq, &done);
@@ -557,7 +557,7 @@
     // Preload the sign of the value.
     __ and_(dst2, int_scratch, Operand(HeapNumber::kSignMask), SetCC);
     // Get the absolute value of the object (as an unsigned integer).
-    __ rsb(int_scratch, int_scratch, Operand(0), SetCC, mi);
+    __ rsb(int_scratch, int_scratch, Operand::Zero(), SetCC, mi);
 
     // Get mantisssa[51:20].
 
@@ -589,7 +589,7 @@
     __ mov(scratch2, Operand(int_scratch, LSL, scratch2));
     __ orr(dst2, dst2, scratch2);
     // Set dst1 to 0.
-    __ mov(dst1, Operand(0));
+    __ mov(dst1, Operand::Zero());
   }
   __ bind(&done);
 }
@@ -657,7 +657,7 @@
     // Check for 0 and -0.
     __ bic(scratch1, dst1, Operand(HeapNumber::kSignMask));
     __ orr(scratch1, scratch1, Operand(dst2));
-    __ cmp(scratch1, Operand(0));
+    __ cmp(scratch1, Operand::Zero());
     __ b(eq, &done);
 
     // Check that the value can be exactly represented by a 32-bit integer.
@@ -730,7 +730,7 @@
     // Check for 0 and -0.
     __ bic(dst, scratch1, Operand(HeapNumber::kSignMask));
     __ orr(dst, scratch2, Operand(dst));
-    __ cmp(dst, Operand(0));
+    __ cmp(dst, Operand::Zero());
     __ b(eq, &done);
 
     DoubleIs32BitInteger(masm, scratch1, scratch2, dst, scratch3, not_int32);
@@ -747,7 +747,7 @@
     // Set the sign.
     __ ldr(scratch1, FieldMemOperand(object, HeapNumber::kExponentOffset));
     __ tst(scratch1, Operand(HeapNumber::kSignMask));
-    __ rsb(dst, dst, Operand(0), LeaveCC, mi);
+    __ rsb(dst, dst, Operand::Zero(), LeaveCC, mi);
   }
 
   __ bind(&done);
@@ -1603,83 +1603,113 @@
 }
 
 
-// The stub returns zero for false, and a non-zero value for true.
+// The stub expects its argument in the tos_ register and returns its result in
+// it, too: zero for false, and a non-zero value for true.
 void ToBooleanStub::Generate(MacroAssembler* masm) {
   // This stub uses VFP3 instructions.
   CpuFeatures::Scope scope(VFP3);
 
-  Label false_result, true_result, not_string;
+  Label patch;
   const Register map = r9.is(tos_) ? r7 : r9;
 
-  // undefined -> false
-  __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-  __ cmp(tos_, ip);
-  __ b(eq, &false_result);
+  // undefined -> false.
+  CheckOddball(masm, UNDEFINED, Heap::kUndefinedValueRootIndex, false);
 
-  // Boolean -> its value
-  __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-  __ cmp(tos_, ip);
-  __ b(eq, &false_result);
-  __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-  __ cmp(tos_, ip);
-  // "tos_" is a register and contains a non-zero value.  Hence we implicitly
-  // return true if the equal condition is satisfied.
-  __ Ret(eq);
+  // Boolean -> its value.
+  CheckOddball(masm, BOOLEAN, Heap::kFalseValueRootIndex, false);
+  CheckOddball(masm, BOOLEAN, Heap::kTrueValueRootIndex, true);
 
-  // Smis: 0 -> false, all other -> true
-  __ tst(tos_, tos_);
-  __ b(eq, &false_result);
-  __ tst(tos_, Operand(kSmiTagMask));
-  // "tos_" is a register and contains a non-zero value.  Hence we implicitly
-  // return true if the not equal condition is satisfied.
-  __ Ret(eq);
+  // 'null' -> false.
+  CheckOddball(masm, NULL_TYPE, Heap::kNullValueRootIndex, false);
 
-  // 'null' -> false
-  __ LoadRoot(ip, Heap::kNullValueRootIndex);
-  __ cmp(tos_, ip);
-  __ b(eq, &false_result);
+  if (types_.Contains(SMI)) {
+    // Smis: 0 -> false, all other -> true
+    __ tst(tos_, Operand(kSmiTagMask));
+    // tos_ contains the correct return value already
+    __ Ret(eq);
+  } else if (types_.NeedsMap()) {
+    // If we need a map later and have a Smi -> patch.
+    __ JumpIfSmi(tos_, &patch);
+  }
 
-  // Get the map of the heap object.
-  __ ldr(map, FieldMemOperand(tos_, HeapObject::kMapOffset));
+  if (types_.NeedsMap()) {
+    __ ldr(map, FieldMemOperand(tos_, HeapObject::kMapOffset));
 
-  // Undetectable -> false.
-  __ ldrb(ip, FieldMemOperand(map, Map::kBitFieldOffset));
-  __ tst(ip, Operand(1 << Map::kIsUndetectable));
-  __ b(&false_result, ne);
+    if (types_.CanBeUndetectable()) {
+      __ ldrb(ip, FieldMemOperand(map, Map::kBitFieldOffset));
+      __ tst(ip, Operand(1 << Map::kIsUndetectable));
+      // Undetectable -> false.
+      __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, ne);
+      __ Ret(ne);
+    }
+  }
 
-  // JavaScript object -> true.
-  __ CompareInstanceType(map, ip, FIRST_SPEC_OBJECT_TYPE);
-  // "tos_" is a register and contains a non-zero value. Hence we implicitly
-  // return true if the greater than condition is satisfied.
-  __ Ret(ge);
+  if (types_.Contains(SPEC_OBJECT)) {
+    // Spec object -> true.
+    __ CompareInstanceType(map, ip, FIRST_SPEC_OBJECT_TYPE);
+    // tos_ contains the correct non-zero return value already.
+    __ Ret(ge);
+  }
 
-  // String value -> false iff empty.
+  if (types_.Contains(STRING)) {
+    // String value -> false iff empty.
   __ CompareInstanceType(map, ip, FIRST_NONSTRING_TYPE);
-  __ b(&not_string, ge);
-  __ ldr(tos_, FieldMemOperand(tos_, String::kLengthOffset));
-  // Return string length as boolean value, i.e. return false iff length is 0.
-  __ Ret();
+  __ ldr(tos_, FieldMemOperand(tos_, String::kLengthOffset), lt);
+  __ Ret(lt);  // the string length is OK as the return value
+  }
 
-  __ bind(&not_string);
-  // HeapNumber -> false iff +0, -0, or NaN.
-  __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
-  __ b(&true_result, ne);
-  __ vldr(d1, FieldMemOperand(tos_, HeapNumber::kValueOffset));
-  __ VFPCompareAndSetFlags(d1, 0.0);
-  // "tos_" is a register, and contains a non zero value by default.
-  // Hence we only need to overwrite "tos_" with zero to return false for
-  // FP_ZERO or FP_NAN cases. Otherwise, by default it returns true.
-  __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, eq);  // for FP_ZERO
-  __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, vs);  // for FP_NAN
-  __ Ret();
+  if (types_.Contains(HEAP_NUMBER)) {
+    // Heap number -> false iff +0, -0, or NaN.
+    Label not_heap_number;
+    __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
+    __ b(ne, &not_heap_number);
+    __ vldr(d1, FieldMemOperand(tos_, HeapNumber::kValueOffset));
+    __ VFPCompareAndSetFlags(d1, 0.0);
+    // "tos_" is a register, and contains a non zero value by default.
+    // Hence we only need to overwrite "tos_" with zero to return false for
+    // FP_ZERO or FP_NAN cases. Otherwise, by default it returns true.
+    __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, eq);  // for FP_ZERO
+    __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, vs);  // for FP_NAN
+    __ Ret();
+    __ bind(&not_heap_number);
+  }
 
-  // Return 1/0 for true/false in tos_.
-  __ bind(&true_result);
-  __ mov(tos_, Operand(1, RelocInfo::NONE));
-  __ Ret();
-  __ bind(&false_result);
-  __ mov(tos_, Operand(0, RelocInfo::NONE));
-  __ Ret();
+  __ bind(&patch);
+  GenerateTypeTransition(masm);
+}
+
+
+void ToBooleanStub::CheckOddball(MacroAssembler* masm,
+                                 Type type,
+                                 Heap::RootListIndex value,
+                                 bool result) {
+  if (types_.Contains(type)) {
+    // If we see an expected oddball, return its ToBoolean value tos_.
+    __ LoadRoot(ip, value);
+    __ cmp(tos_, ip);
+    // The value of a root is never NULL, so we can avoid loading a non-null
+    // value into tos_ when we want to return 'true'.
+    if (!result) {
+      __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, eq);
+    }
+    __ Ret(eq);
+  }
+}
+
+
+void ToBooleanStub::GenerateTypeTransition(MacroAssembler* masm) {
+  if (!tos_.is(r3)) {
+    __ mov(r3, Operand(tos_));
+  }
+  __ mov(r2, Operand(Smi::FromInt(tos_.code())));
+  __ mov(r1, Operand(Smi::FromInt(types_.ToByte())));
+  __ Push(r3, r2, r1);
+  // Patch the caller to an appropriate specialized stub and return the
+  // operation result to the caller of the stub.
+  __ TailCallExternalReference(
+      ExternalReference(IC_Utility(IC::kToBoolean_Patch), masm->isolate()),
+      3,
+      1);
 }
 
 
@@ -2394,7 +2424,6 @@
   Register left = r1;
   Register right = r0;
   Register scratch1 = r7;
-  Register scratch2 = r9;
 
   // Perform combined smi check on both operands.
   __ orr(scratch1, left, Operand(right));
@@ -2588,7 +2617,7 @@
           __ b(mi, &return_heap_number);
           // Check for minus zero. Return heap number for minus zero.
           Label not_zero;
-          __ cmp(scratch1, Operand(0));
+          __ cmp(scratch1, Operand::Zero());
           __ b(ne, &not_zero);
           __ vmov(scratch2, d5.high());
           __ tst(scratch2, Operand(HeapNumber::kSignMask));
@@ -3080,7 +3109,6 @@
 
     Label no_update;
     Label skip_cache;
-    const Register heap_number_map = r5;
 
     // Call C function to calculate the result and update the cache.
     // Register r0 holds precalculated cache entry address; preserve
@@ -3551,7 +3579,7 @@
   ExternalReference js_entry_sp(Isolate::k_js_entry_sp_address, isolate);
   __ mov(r5, Operand(ExternalReference(js_entry_sp)));
   __ ldr(r6, MemOperand(r5));
-  __ cmp(r6, Operand(0));
+  __ cmp(r6, Operand::Zero());
   __ b(ne, &non_outermost_js);
   __ str(fp, MemOperand(r5));
   __ mov(ip, Operand(Smi::FromInt(StackFrame::OUTERMOST_JSENTRY_FRAME)));
@@ -3626,7 +3654,7 @@
   __ pop(r5);
   __ cmp(r5, Operand(Smi::FromInt(StackFrame::OUTERMOST_JSENTRY_FRAME)));
   __ b(ne, &non_outermost_js_2);
-  __ mov(r6, Operand(0));
+  __ mov(r6, Operand::Zero());
   __ mov(r5, Operand(ExternalReference(js_entry_sp)));
   __ str(r6, MemOperand(r5));
   __ bind(&non_outermost_js_2);
@@ -3827,7 +3855,7 @@
     __ Push(r0, r1);
     __ InvokeBuiltin(Builtins::INSTANCE_OF, CALL_FUNCTION);
     __ LeaveInternalFrame();
-    __ cmp(r0, Operand(0));
+    __ cmp(r0, Operand::Zero());
     __ LoadRoot(r0, Heap::kTrueValueRootIndex, eq);
     __ LoadRoot(r0, Heap::kFalseValueRootIndex, ne);
     __ Ret(HasArgsInRegisters() ? 0 : 2);
@@ -3961,7 +3989,7 @@
       FixedArray::kHeaderSize + 2 * kPointerSize;
   // If there are no mapped parameters, we do not need the parameter_map.
   __ cmp(r1, Operand(Smi::FromInt(0)));
-  __ mov(r9, Operand(0), LeaveCC, eq);
+  __ mov(r9, Operand::Zero(), LeaveCC, eq);
   __ mov(r9, Operand(r1, LSL, 1), LeaveCC, ne);
   __ add(r9, r9, Operand(kParameterMapHeaderSize), LeaveCC, ne);
 
@@ -3985,7 +4013,7 @@
 
   __ ldr(r4, MemOperand(r8, Context::SlotOffset(Context::GLOBAL_INDEX)));
   __ ldr(r4, FieldMemOperand(r4, GlobalObject::kGlobalContextOffset));
-  __ cmp(r1, Operand(0));
+  __ cmp(r1, Operand::Zero());
   __ ldr(r4, MemOperand(r4, kNormalOffset), eq);
   __ ldr(r4, MemOperand(r4, kAliasedOffset), ne);
 
@@ -4339,6 +4367,8 @@
   __ cmp(r2, Operand(r0, ASR, kSmiTagSize));
   __ b(gt, &runtime);
 
+  // Reset offset for possibly sliced string.
+  __ mov(r9, Operand(0));
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
   // Check the representation and encoding of the subject string.
@@ -4346,33 +4376,45 @@
   __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
   // First check for flat string.
-  __ tst(r0, Operand(kIsNotStringMask | kStringRepresentationMask));
+  __ and_(r1, r0, Operand(kIsNotStringMask | kStringRepresentationMask), SetCC);
   STATIC_ASSERT((kStringTag | kSeqStringTag) == 0);
   __ b(eq, &seq_string);
 
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
-  // Check for flat cons string.
+  // Check for flat cons string or sliced string.
   // A flat cons string is a cons string where the second part is the empty
   // string. In that case the subject string is just the first part of the cons
   // string. Also in this case the first part of the cons string is known to be
   // a sequential string or an external string.
-  STATIC_ASSERT(kExternalStringTag !=0);
-  STATIC_ASSERT((kConsStringTag & kExternalStringTag) == 0);
-  __ tst(r0, Operand(kIsNotStringMask | kExternalStringTag));
-  __ b(ne, &runtime);
+  // In the case of a sliced string its offset has to be taken into account.
+  Label cons_string, check_encoding;
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ cmp(r1, Operand(kExternalStringTag));
+  __ b(lt, &cons_string);
+  __ b(eq, &runtime);
+
+  // String is sliced.
+  __ ldr(r9, FieldMemOperand(subject, SlicedString::kOffsetOffset));
+  __ mov(r9, Operand(r9, ASR, kSmiTagSize));
+  __ ldr(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
+  // r9: offset of sliced string, smi-tagged.
+  __ jmp(&check_encoding);
+  // String is a cons string, check whether it is flat.
+  __ bind(&cons_string);
   __ ldr(r0, FieldMemOperand(subject, ConsString::kSecondOffset));
   __ LoadRoot(r1, Heap::kEmptyStringRootIndex);
   __ cmp(r0, r1);
   __ b(ne, &runtime);
   __ ldr(subject, FieldMemOperand(subject, ConsString::kFirstOffset));
+  // Is first part of cons or parent of slice a flat string?
+  __ bind(&check_encoding);
   __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
-  // Is first part a flat string?
   STATIC_ASSERT(kSeqStringTag == 0);
   __ tst(r0, Operand(kStringRepresentationMask));
   __ b(ne, &runtime);
-
   __ bind(&seq_string);
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
@@ -4438,21 +4480,30 @@
 
   // For arguments 4 and 3 get string length, calculate start of string data and
   // calculate the shift of the index (0 for ASCII and 1 for two byte).
-  __ ldr(r0, FieldMemOperand(subject, String::kLengthOffset));
-  __ mov(r0, Operand(r0, ASR, kSmiTagSize));
   STATIC_ASSERT(SeqAsciiString::kHeaderSize == SeqTwoByteString::kHeaderSize);
-  __ add(r9, subject, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ add(r8, subject, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
   __ eor(r3, r3, Operand(1));
-  // Argument 4 (r3): End of string data
-  // Argument 3 (r2): Start of string data
+  // Load the length from the original subject string from the previous stack
+  // frame. Therefore we have to use fp, which points exactly to two pointer
+  // sizes below the previous sp. (Because creating a new stack frame pushes
+  // the previous fp onto the stack and moves up sp by 2 * kPointerSize.)
+  __ ldr(r0, MemOperand(fp, kSubjectOffset + 2 * kPointerSize));
+  // If slice offset is not 0, load the length from the original sliced string.
+  // Argument 4, r3: End of string data
+  // Argument 3, r2: Start of string data
+  // Prepare start and end index of the input.
+  __ add(r9, r8, Operand(r9, LSL, r3));
   __ add(r2, r9, Operand(r1, LSL, r3));
-  __ add(r3, r9, Operand(r0, LSL, r3));
+
+  __ ldr(r8, FieldMemOperand(r0, String::kLengthOffset));
+  __ mov(r8, Operand(r8, ASR, kSmiTagSize));
+  __ add(r3, r9, Operand(r8, LSL, r3));
 
   // Argument 2 (r1): Previous index.
   // Already there
 
   // Argument 1 (r0): Subject string.
-  __ mov(r0, subject);
+  // Already there
 
   // Locate the code entry and call it.
   __ add(r7, r7, Operand(Code::kHeaderSize - kHeapObjectTag));
@@ -4469,12 +4520,12 @@
   // Check the result.
   Label success;
 
-  __ cmp(r0, Operand(NativeRegExpMacroAssembler::SUCCESS));
+  __ cmp(subject, Operand(NativeRegExpMacroAssembler::SUCCESS));
   __ b(eq, &success);
   Label failure;
-  __ cmp(r0, Operand(NativeRegExpMacroAssembler::FAILURE));
+  __ cmp(subject, Operand(NativeRegExpMacroAssembler::FAILURE));
   __ b(eq, &failure);
-  __ cmp(r0, Operand(NativeRegExpMacroAssembler::EXCEPTION));
+  __ cmp(subject, Operand(NativeRegExpMacroAssembler::EXCEPTION));
   // If not exception it can only be retry. Handle that in the runtime system.
   __ b(ne, &runtime);
   // Result must now be exception. If there is no pending exception already a
@@ -4486,18 +4537,18 @@
   __ mov(r2, Operand(ExternalReference(Isolate::k_pending_exception_address,
                                        isolate)));
   __ ldr(r0, MemOperand(r2, 0));
-  __ cmp(r0, r1);
+  __ cmp(subject, r1);
   __ b(eq, &runtime);
 
   __ str(r1, MemOperand(r2, 0));  // Clear pending exception.
 
   // Check if the exception is a termination. If so, throw as uncatchable.
   __ LoadRoot(ip, Heap::kTerminationExceptionRootIndex);
-  __ cmp(r0, ip);
+  __ cmp(subject, ip);
   Label termination_exception;
   __ b(eq, &termination_exception);
 
-  __ Throw(r0);  // Expects thrown value in r0.
+  __ Throw(subject);  // Expects thrown value in r0.
 
   __ bind(&termination_exception);
   __ ThrowUncatchable(TERMINATION, r0);  // Expects thrown value in r0.
@@ -4775,6 +4826,7 @@
   Label flat_string;
   Label ascii_string;
   Label got_char_code;
+  Label sliced_string;
 
   // If the receiver is a smi trigger the non-string case.
   __ JumpIfSmi(object_, receiver_not_string_);
@@ -4804,7 +4856,11 @@
   __ b(eq, &flat_string);
 
   // Handle non-flat strings.
-  __ tst(result_, Operand(kIsConsStringMask));
+  __ and_(result_, result_, Operand(kStringRepresentationMask));
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ cmp(result_, Operand(kExternalStringTag));
+  __ b(gt, &sliced_string);
   __ b(eq, &call_runtime_);
 
   // ConsString.
@@ -4812,15 +4868,26 @@
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
+  Label assure_seq_string;
   __ ldr(result_, FieldMemOperand(object_, ConsString::kSecondOffset));
   __ LoadRoot(ip, Heap::kEmptyStringRootIndex);
   __ cmp(result_, Operand(ip));
   __ b(ne, &call_runtime_);
   // Get the first of the two strings and load its instance type.
   __ ldr(object_, FieldMemOperand(object_, ConsString::kFirstOffset));
+  __ jmp(&assure_seq_string);
+
+  // SlicedString, unpack and add offset.
+  __ bind(&sliced_string);
+  __ ldr(result_, FieldMemOperand(object_, SlicedString::kOffsetOffset));
+  __ add(scratch_, scratch_, result_);
+  __ ldr(object_, FieldMemOperand(object_, SlicedString::kParentOffset));
+
+  // Assure that we are dealing with a sequential string. Go to runtime if not.
+  __ bind(&assure_seq_string);
   __ ldr(result_, FieldMemOperand(object_, HeapObject::kMapOffset));
   __ ldrb(result_, FieldMemOperand(result_, Map::kInstanceTypeOffset));
-  // If the first cons component is also non-flat, then go to runtime.
+  // Check that parent is not an external string. Go to runtime otherwise.
   STATIC_ASSERT(kSeqStringTag == 0);
   __ tst(result_, Operand(kStringRepresentationMask));
   __ b(ne, &call_runtime_);
@@ -5400,10 +5467,17 @@
   // Check bounds and smi-ness.
   Register to = r6;
   Register from = r7;
+
+  if (FLAG_string_slices) {
+    __ nop(0);  // Jumping as first instruction would crash the code generation.
+    __ jmp(&runtime);
+  }
+
   __ Ldrd(to, from, MemOperand(sp, kToOffset));
   STATIC_ASSERT(kFromOffset == kToOffset + 4);
   STATIC_ASSERT(kSmiTag == 0);
   STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 1);
+
   // I.e., arithmetic shift right by one un-smi-tags.
   __ mov(r2, Operand(to, ASR, 1), SetCC);
   __ mov(r3, Operand(from, ASR, 1), SetCC, cc);
@@ -5412,7 +5486,6 @@
   __ b(mi, &runtime);  // From is negative.
 
   // Both to and from are smis.
-
   __ sub(r2, r2, Operand(r3), SetCC);
   __ b(mi, &runtime);  // Fail if from > to.
   // Special handling of sub-strings of length 1 and 2. One character strings
@@ -5667,7 +5740,7 @@
          Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
   __ add(left, left, Operand(scratch1));
   __ add(right, right, Operand(scratch1));
-  __ rsb(length, length, Operand(0));
+  __ rsb(length, length, Operand::Zero());
   Register index = length;  // index = -length;
 
   // Compare loop.
@@ -6285,12 +6358,8 @@
 
 void DirectCEntryStub::GenerateCall(MacroAssembler* masm,
                                     ExternalReference function) {
-  __ mov(lr, Operand(reinterpret_cast<intptr_t>(GetCode().location()),
-                     RelocInfo::CODE_TARGET));
   __ mov(r2, Operand(function));
-  // Push return address (accessible to GC through exit frame pc).
-  __ str(pc, MemOperand(sp, 0));
-  __ Jump(r2);  // Call the api function.
+  GenerateCall(masm, r2);
 }
 
 
@@ -6299,8 +6368,14 @@
   __ mov(lr, Operand(reinterpret_cast<intptr_t>(GetCode().location()),
                      RelocInfo::CODE_TARGET));
   // Push return address (accessible to GC through exit frame pc).
-  __ str(pc, MemOperand(sp, 0));
+  // Note that using pc with str is deprecated.
+  Label start;
+  __ bind(&start);
+  __ add(ip, pc, Operand(Assembler::kInstrSize));
+  __ str(ip, MemOperand(sp, 0));
   __ Jump(target);  // Call the C++ function.
+  ASSERT_EQ(Assembler::kInstrSize + Assembler::kPcLoadDelta,
+            masm->SizeOfCodeGeneratedSince(&start));
 }
 
 
@@ -6523,7 +6598,7 @@
   // treated as a lookup success. For positive lookup probing failure
   // should be treated as lookup failure.
   if (mode_ == POSITIVE_LOOKUP) {
-    __ mov(result, Operand(0));
+    __ mov(result, Operand::Zero());
     __ Ret();
   }
 
@@ -6532,7 +6607,7 @@
   __ Ret();
 
   __ bind(&not_in_dictionary);
-  __ mov(result, Operand(0));
+  __ mov(result, Operand::Zero());
   __ Ret();
 }
 
diff --git a/src/arm/deoptimizer-arm.cc b/src/arm/deoptimizer-arm.cc
index 4b994e5..00357f7 100644
--- a/src/arm/deoptimizer-arm.cc
+++ b/src/arm/deoptimizer-arm.cc
@@ -35,7 +35,7 @@
 namespace v8 {
 namespace internal {
 
-int Deoptimizer::table_entry_size_ = 16;
+const int Deoptimizer::table_entry_size_ = 16;
 
 
 int Deoptimizer::patch_size() {
@@ -533,8 +533,6 @@
     output_frame->SetContinuation(
         reinterpret_cast<uint32_t>(continuation->entry()));
   }
-
-  if (output_count_ - 1 == frame_index) iterator->Done();
 }
 
 
@@ -595,6 +593,8 @@
   __ vstm(db_w, sp, first, last);
 
   // Push all 16 registers (needed to populate FrameDescription::registers_).
+  // TODO(1588) Note that using pc with stm is deprecated, so we should perhaps
+  // handle this a bit differently.
   __ stm(db_w, sp, restored_regs  | sp.bit() | lr.bit() | pc.bit());
 
   const int kSavedRegistersAreaSize =
diff --git a/src/arm/disasm-arm.cc b/src/arm/disasm-arm.cc
index d4bd81c..603b3cf 100644
--- a/src/arm/disasm-arm.cc
+++ b/src/arm/disasm-arm.cc
@@ -200,7 +200,7 @@
 
 // These shift names are defined in a way to match the native disassembler
 // formatting. See for example the command "objdump -d <binary file>".
-static const char* shift_names[kNumberOfShifts] = {
+static const char* const shift_names[kNumberOfShifts] = {
   "lsl", "lsr", "asr", "ror"
 };
 
diff --git a/src/arm/frames-arm.h b/src/arm/frames-arm.h
index 84e108b..26bbd82 100644
--- a/src/arm/frames-arm.h
+++ b/src/arm/frames-arm.h
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -93,10 +93,11 @@
 
 class StackHandlerConstants : public AllStatic {
  public:
-  static const int kNextOffset  = 0 * kPointerSize;
-  static const int kStateOffset = 1 * kPointerSize;
-  static const int kFPOffset    = 2 * kPointerSize;
-  static const int kPCOffset    = 3 * kPointerSize;
+  static const int kNextOffset    = 0 * kPointerSize;
+  static const int kStateOffset   = 1 * kPointerSize;
+  static const int kContextOffset = 2 * kPointerSize;
+  static const int kFPOffset      = 3 * kPointerSize;
+  static const int kPCOffset      = 4 * kPointerSize;
 
   static const int kSize = kPCOffset + kPointerSize;
 };
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index c3440eb..1604883 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -47,7 +47,6 @@
 
 
 static unsigned GetPropertyId(Property* property) {
-  if (property->is_synthetic()) return AstNode::kNoNumber;
   return property->id();
 }
 
@@ -694,104 +693,73 @@
   Comment cmnt(masm_, "[ Declaration");
   ASSERT(variable != NULL);  // Must have been resolved.
   Slot* slot = variable->AsSlot();
-  Property* prop = variable->AsProperty();
-
-  if (slot != NULL) {
-    switch (slot->type()) {
-      case Slot::PARAMETER:
-      case Slot::LOCAL:
-        if (mode == Variable::CONST) {
-          __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
-          __ str(ip, MemOperand(fp, SlotOffset(slot)));
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ str(result_register(), MemOperand(fp, SlotOffset(slot)));
-        }
-        break;
-
-      case Slot::CONTEXT:
-        // We bypass the general EmitSlotSearch because we know more about
-        // this specific context.
-
-        // The variable in the decl always resides in the current function
-        // context.
-        ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
-        if (FLAG_debug_code) {
-          // Check that we're not inside a with or catch context.
-          __ ldr(r1, FieldMemOperand(cp, HeapObject::kMapOffset));
-          __ CompareRoot(r1, Heap::kWithContextMapRootIndex);
-          __ Check(ne, "Declaration in with context.");
-          __ CompareRoot(r1, Heap::kCatchContextMapRootIndex);
-          __ Check(ne, "Declaration in catch context.");
-        }
-        if (mode == Variable::CONST) {
-          __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
-          __ str(ip, ContextOperand(cp, slot->index()));
-          // No write barrier since the_hole_value is in old space.
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ str(result_register(), ContextOperand(cp, slot->index()));
-          int offset = Context::SlotOffset(slot->index());
-          // We know that we have written a function, which is not a smi.
-          __ mov(r1, Operand(cp));
-          __ RecordWrite(r1, Operand(offset), r2, result_register());
-        }
-        break;
-
-      case Slot::LOOKUP: {
-        __ mov(r2, Operand(variable->name()));
-        // Declaration nodes are always introduced in one of two modes.
-        ASSERT(mode == Variable::VAR ||
-               mode == Variable::CONST);
-        PropertyAttributes attr =
-            (mode == Variable::VAR) ? NONE : READ_ONLY;
-        __ mov(r1, Operand(Smi::FromInt(attr)));
-        // Push initial value, if any.
-        // Note: For variables we must not push an initial value (such as
-        // 'undefined') because we may have a (legal) redeclaration and we
-        // must not destroy the current value.
-        if (mode == Variable::CONST) {
-          __ LoadRoot(r0, Heap::kTheHoleValueRootIndex);
-          __ Push(cp, r2, r1, r0);
-        } else if (function != NULL) {
-          __ Push(cp, r2, r1);
-          // Push initial value for function declaration.
-          VisitForStackValue(function);
-        } else {
-          __ mov(r0, Operand(Smi::FromInt(0)));  // No initial value!
-          __ Push(cp, r2, r1, r0);
-        }
-        __ CallRuntime(Runtime::kDeclareContextSlot, 4);
-        break;
+  ASSERT(slot != NULL);
+  switch (slot->type()) {
+    case Slot::PARAMETER:
+    case Slot::LOCAL:
+      if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ str(result_register(), MemOperand(fp, SlotOffset(slot)));
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
+        __ str(ip, MemOperand(fp, SlotOffset(slot)));
       }
-    }
+      break;
 
-  } else if (prop != NULL) {
-    // A const declaration aliasing a parameter is an illegal redeclaration.
-    ASSERT(mode != Variable::CONST);
-    if (function != NULL) {
-      // We are declaring a function that rewrites to a property.
-      // Use (keyed) IC to set the initial value.  We cannot visit the
-      // rewrite because it's shared and we risk recording duplicate AST
-      // IDs for bailouts from optimized code.
-      ASSERT(prop->obj()->AsVariableProxy() != NULL);
-      { AccumulatorValueContext for_object(this);
-        EmitVariableLoad(prop->obj()->AsVariableProxy());
+    case Slot::CONTEXT:
+      // We bypass the general EmitSlotSearch because we know more about
+      // this specific context.
+
+      // The variable in the decl always resides in the current function
+      // context.
+      ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
+      if (FLAG_debug_code) {
+        // Check that we're not inside a with or catch context.
+        __ ldr(r1, FieldMemOperand(cp, HeapObject::kMapOffset));
+        __ CompareRoot(r1, Heap::kWithContextMapRootIndex);
+        __ Check(ne, "Declaration in with context.");
+        __ CompareRoot(r1, Heap::kCatchContextMapRootIndex);
+        __ Check(ne, "Declaration in catch context.");
       }
+      if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ str(result_register(), ContextOperand(cp, slot->index()));
+        int offset = Context::SlotOffset(slot->index());
+        // We know that we have written a function, which is not a smi.
+        __ mov(r1, Operand(cp));
+        __ RecordWrite(r1, Operand(offset), r2, result_register());
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
+        __ str(ip, ContextOperand(cp, slot->index()));
+        // No write barrier since the_hole_value is in old space.
+      }
+      break;
 
-      __ push(r0);
-      VisitForAccumulatorValue(function);
-      __ pop(r2);
-
-      ASSERT(prop->key()->AsLiteral() != NULL &&
-             prop->key()->AsLiteral()->handle()->IsSmi());
-      __ mov(r1, Operand(prop->key()->AsLiteral()->handle()));
-
-      Handle<Code> ic = is_strict_mode()
-          ? isolate()->builtins()->KeyedStoreIC_Initialize_Strict()
-          : isolate()->builtins()->KeyedStoreIC_Initialize();
-      __ Call(ic);
-      // Value in r0 is ignored (declarations are statements).
+    case Slot::LOOKUP: {
+      __ mov(r2, Operand(variable->name()));
+      // Declaration nodes are always introduced in one of two modes.
+      ASSERT(mode == Variable::VAR ||
+             mode == Variable::CONST ||
+             mode == Variable::LET);
+      PropertyAttributes attr = (mode == Variable::CONST) ? READ_ONLY : NONE;
+      __ mov(r1, Operand(Smi::FromInt(attr)));
+      // Push initial value, if any.
+      // Note: For variables we must not push an initial value (such as
+      // 'undefined') because we may have a (legal) redeclaration and we
+      // must not destroy the current value.
+      if (function != NULL) {
+        __ Push(cp, r2, r1);
+        // Push initial value for function declaration.
+        VisitForStackValue(function);
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ LoadRoot(r0, Heap::kTheHoleValueRootIndex);
+        __ Push(cp, r2, r1, r0);
+      } else {
+        __ mov(r0, Operand(Smi::FromInt(0)));  // No initial value!
+        __ Push(cp, r2, r1, r0);
+      }
+      __ CallRuntime(Runtime::kDeclareContextSlot, 4);
+      break;
     }
   }
 }
@@ -878,7 +846,7 @@
   __ bind(&next_test);
   __ Drop(1);  // Switch value is no longer needed.
   if (default_clause == NULL) {
-    __ b(nested_statement.break_target());
+    __ b(nested_statement.break_label());
   } else {
     __ b(default_clause->body_target());
   }
@@ -892,7 +860,7 @@
     VisitStatements(clause->statements());
   }
 
-  __ bind(nested_statement.break_target());
+  __ bind(nested_statement.break_label());
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
 }
 
@@ -1023,7 +991,7 @@
   // Load the current count to r0, load the length to r1.
   __ Ldrd(r0, r1, MemOperand(sp, 0 * kPointerSize));
   __ cmp(r0, r1);  // Compare to the array length.
-  __ b(hs, loop_statement.break_target());
+  __ b(hs, loop_statement.break_label());
 
   // Get the current entry of the array into register r3.
   __ ldr(r2, MemOperand(sp, 2 * kPointerSize));
@@ -1049,7 +1017,7 @@
   __ push(r3);  // Current entry.
   __ InvokeBuiltin(Builtins::FILTER_KEY, CALL_FUNCTION);
   __ mov(r3, Operand(r0), SetCC);
-  __ b(eq, loop_statement.continue_target());
+  __ b(eq, loop_statement.continue_label());
 
   // Update the 'each' property or variable from the possibly filtered
   // entry in register r3.
@@ -1065,7 +1033,7 @@
 
   // Generate code for the going to the next element by incrementing
   // the index (smi) stored on top of the stack.
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   __ pop(r0);
   __ add(r0, r0, Operand(Smi::FromInt(1)));
   __ push(r0);
@@ -1074,7 +1042,7 @@
   __ b(&loop);
 
   // Remove the pointers stored on the stack.
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   __ Drop(5);
 
   // Exit and decrement the loop depth.
@@ -1311,6 +1279,20 @@
       __ cmp(r0, ip);
       __ LoadRoot(r0, Heap::kUndefinedValueRootIndex, eq);
       context()->Plug(r0);
+    } else if (var->mode() == Variable::LET) {
+      // Let bindings may be the hole value if they have not been initialized.
+      // Throw a type error in this case.
+      Label done;
+      MemOperand slot_operand = EmitSlotSearch(slot, r0);
+      __ ldr(r0, slot_operand);
+      __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
+      __ cmp(r0, ip);
+      __ b(ne, &done);
+      __ mov(r0, Operand(var->name()));
+      __ push(r0);
+      __ CallRuntime(Runtime::kThrowReferenceError, 1);
+      __ bind(&done);
+      context()->Plug(r0);
     } else {
       context()->Plug(slot);
     }
@@ -1891,6 +1873,59 @@
     }
     __ bind(&skip);
 
+  } else if (var->mode() == Variable::LET && op != Token::INIT_LET) {
+    // Perform the assignment for non-const variables.  Const assignments
+    // are simply skipped.
+    Slot* slot = var->AsSlot();
+    switch (slot->type()) {
+      case Slot::PARAMETER:
+      case Slot::LOCAL: {
+        Label assign;
+        // Check for an initialized let binding.
+        __ ldr(r1, MemOperand(fp, SlotOffset(slot)));
+        __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
+        __ cmp(r1, ip);
+        __ b(ne, &assign);
+        __ mov(r1, Operand(var->name()));
+        __ push(r1);
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+        // Perform the assignment.
+        __ bind(&assign);
+        __ str(result_register(), MemOperand(fp, SlotOffset(slot)));
+        break;
+      }
+      case Slot::CONTEXT: {
+        // Let variables may be the hole value if they have not been
+        // initialized. Throw a type error in this case.
+        Label assign;
+        MemOperand target = EmitSlotSearch(slot, r1);
+        // Check for an initialized let binding.
+        __ ldr(r3, target);
+        __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
+        __ cmp(r3, ip);
+        __ b(ne, &assign);
+        __ mov(r3, Operand(var->name()));
+        __ push(r3);
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+        // Perform the assignment.
+        __ bind(&assign);
+        __ str(result_register(), target);
+        // RecordWrite may destroy all its register arguments.
+        __ mov(r3, result_register());
+        int offset = Context::SlotOffset(slot->index());
+        __ RecordWrite(r1, Operand(offset), r2, r3);
+        break;
+      }
+      case Slot::LOOKUP:
+        // Call the runtime for the assignment.
+        __ push(r0);  // Value.
+        __ mov(r1, Operand(slot->var()->name()));
+        __ mov(r0, Operand(Smi::FromInt(strict_mode_flag())));
+        __ Push(cp, r1, r0);  // Context, name, strict mode.
+        __ CallRuntime(Runtime::kStoreContextSlot, 4);
+        break;
+    }
+
   } else if (var->mode() != Variable::CONST) {
     // Perform the assignment for non-const variables.  Const assignments
     // are simply skipped.
@@ -2272,36 +2307,10 @@
       EmitCallWithIC(expr, key->handle(), RelocInfo::CODE_TARGET);
     } else {
       // Call to a keyed property.
-      // For a synthetic property use keyed load IC followed by function call,
-      // for a regular property use EmitKeyedCallWithIC.
-      if (prop->is_synthetic()) {
-        // Do not visit the object and key subexpressions (they are shared
-        // by all occurrences of the same rewritten parameter).
-        ASSERT(prop->obj()->AsVariableProxy() != NULL);
-        ASSERT(prop->obj()->AsVariableProxy()->var()->AsSlot() != NULL);
-        Slot* slot = prop->obj()->AsVariableProxy()->var()->AsSlot();
-        MemOperand operand = EmitSlotSearch(slot, r1);
-        __ ldr(r1, operand);
-
-        ASSERT(prop->key()->AsLiteral() != NULL);
-        ASSERT(prop->key()->AsLiteral()->handle()->IsSmi());
-        __ mov(r0, Operand(prop->key()->AsLiteral()->handle()));
-
-        // Record source code position for IC call.
-        SetSourcePosition(prop->position());
-
-        Handle<Code> ic = isolate()->builtins()->KeyedLoadIC_Initialize();
-        __ Call(ic, RelocInfo::CODE_TARGET, GetPropertyId(prop));
-        __ ldr(r1, GlobalObjectOperand());
-        __ ldr(r1, FieldMemOperand(r1, GlobalObject::kGlobalReceiverOffset));
-        __ Push(r0, r1);  // Function, receiver.
-        EmitCallWithStub(expr, NO_CALL_FUNCTION_FLAGS);
-      } else {
-        { PreservePositionScope scope(masm()->positions_recorder());
-          VisitForStackValue(prop->obj());
-        }
-        EmitKeyedCallWithIC(expr, prop->key());
+      { PreservePositionScope scope(masm()->positions_recorder());
+        VisitForStackValue(prop->obj());
       }
+      EmitKeyedCallWithIC(expr, prop->key());
     }
   } else {
     { PreservePositionScope scope(masm()->positions_recorder());
@@ -2753,7 +2762,7 @@
 
   // Objects with a non-function constructor have class 'Object'.
   __ bind(&non_function_constructor);
-  __ LoadRoot(r0, Heap::kfunction_class_symbolRootIndex);
+  __ LoadRoot(r0, Heap::kObject_symbolRootIndex);
   __ jmp(&done);
 
   // Non-JS objects have class null.
@@ -3252,7 +3261,7 @@
 
   Label done, not_found;
   // tmp now holds finger offset as a smi.
-  ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
   __ ldr(r2, FieldMemOperand(cache, JSFunctionResultCache::kFingerOffset));
   // r2 now holds finger offset as a smi.
   __ add(r3, cache, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
@@ -3580,39 +3589,6 @@
 }
 
 
-void FullCodeGenerator::EmitIsNativeOrStrictMode(ZoneList<Expression*>* args) {
-  ASSERT(args->length() == 1);
-
-  // Load the function into r0.
-  VisitForAccumulatorValue(args->at(0));
-
-  // Prepare for the test.
-  Label materialize_true, materialize_false;
-  Label* if_true = NULL;
-  Label* if_false = NULL;
-  Label* fall_through = NULL;
-  context()->PrepareTest(&materialize_true, &materialize_false,
-                         &if_true, &if_false, &fall_through);
-
-  // Test for strict mode function.
-  __ ldr(r1, FieldMemOperand(r0, JSFunction::kSharedFunctionInfoOffset));
-  __ ldr(r1, FieldMemOperand(r1, SharedFunctionInfo::kCompilerHintsOffset));
-  __ tst(r1, Operand(1 << (SharedFunctionInfo::kStrictModeFunction +
-                           kSmiTagSize)));
-  __ b(ne, if_true);
-
-  // Test for native function.
-  __ tst(r1, Operand(1 << (SharedFunctionInfo::kNative + kSmiTagSize)));
-  __ b(ne, if_true);
-
-  // Not native or strict-mode function.
-  __ b(if_false);
-
-  PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
-  context()->Plug(if_true, if_false);
-}
-
-
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   Handle<String> name = expr->name();
   if (name->length() > 0 && name->Get(0) == '_') {
@@ -3664,18 +3640,12 @@
       Variable* var = expr->expression()->AsVariableProxy()->AsVariable();
 
       if (prop != NULL) {
-        if (prop->is_synthetic()) {
-          // Result of deleting parameters is false, even when they rewrite
-          // to accesses on the arguments object.
-          context()->Plug(false);
-        } else {
-          VisitForStackValue(prop->obj());
-          VisitForStackValue(prop->key());
-          __ mov(r1, Operand(Smi::FromInt(strict_mode_flag())));
-          __ push(r1);
-          __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
-          context()->Plug(r0);
-        }
+        VisitForStackValue(prop->obj());
+        VisitForStackValue(prop->key());
+        __ mov(r1, Operand(Smi::FromInt(strict_mode_flag())));
+        __ push(r1);
+        __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
+        context()->Plug(r0);
       } else if (var != NULL) {
         // Delete of an unqualified identifier is disallowed in strict mode
         // but "delete this" is.
@@ -4030,6 +4000,10 @@
     __ b(eq, if_true);
     __ CompareRoot(r0, Heap::kFalseValueRootIndex);
     Split(eq, if_true, if_false, fall_through);
+  } else if (FLAG_harmony_typeof &&
+             check->Equals(isolate()->heap()->null_symbol())) {
+    __ CompareRoot(r0, Heap::kNullValueRootIndex);
+    Split(eq, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->undefined_symbol())) {
     __ CompareRoot(r0, Heap::kUndefinedValueRootIndex);
     __ b(eq, if_true);
@@ -4047,8 +4021,10 @@
 
   } else if (check->Equals(isolate()->heap()->object_symbol())) {
     __ JumpIfSmi(r0, if_false);
-    __ CompareRoot(r0, Heap::kNullValueRootIndex);
-    __ b(eq, if_true);
+    if (!FLAG_harmony_typeof) {
+      __ CompareRoot(r0, Heap::kNullValueRootIndex);
+      __ b(eq, if_true);
+    }
     // Check for JS objects => true.
     __ CompareObjectType(r0, r0, r1, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE);
     __ b(lt, if_false);
@@ -4123,11 +4099,8 @@
     default: {
       VisitForAccumulatorValue(expr->right());
       Condition cond = eq;
-      bool strict = false;
       switch (op) {
         case Token::EQ_STRICT:
-          strict = true;
-          // Fall through
         case Token::EQ:
           cond = eq;
           __ pop(r1);
@@ -4276,7 +4249,7 @@
   // Cook return address in link register to stack (smi encoded Code* delta)
   __ sub(r1, lr, Operand(masm_->CodeObject()));
   ASSERT_EQ(1, kSmiTagSize + kSmiShiftSize);
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   __ add(r1, r1, Operand(r1));  // Convert to smi.
   __ push(r1);
 }
@@ -4296,6 +4269,34 @@
 
 #undef __
 
+#define __ ACCESS_MASM(masm())
+
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
+    int* stack_depth,
+    int* context_length) {
+  // The macros used here must preserve the result register.
+
+  // Because the handler block contains the context of the finally
+  // code, we can restore it directly from there for the finally code
+  // rather than iteratively unwinding contexts via their previous
+  // links.
+  __ Drop(*stack_depth);  // Down to the handler block.
+  if (*context_length > 0) {
+    // Restore the context to its dedicated register and the stack.
+    __ ldr(cp, MemOperand(sp, StackHandlerConstants::kContextOffset));
+    __ str(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
+  }
+  __ PopTryHandler();
+  __ bl(finally_entry_);
+
+  *stack_depth = 0;
+  *context_length = 0;
+  return previous_;
+}
+
+
+#undef __
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM
diff --git a/src/arm/ic-arm.cc b/src/arm/ic-arm.cc
index 6038153..6bad5ac 100644
--- a/src/arm/ic-arm.cc
+++ b/src/arm/ic-arm.cc
@@ -337,7 +337,7 @@
   // Fast case: Do the load.
   __ add(scratch1, elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
   // The key is a smi.
-  ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
   __ ldr(scratch2,
          MemOperand(scratch1, key, LSL, kPointerSizeLog2 - kSmiTagSize));
   __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
@@ -370,7 +370,7 @@
   // Is the string a symbol?
   // map: key map
   __ ldrb(hash, FieldMemOperand(map, Map::kInstanceTypeOffset));
-  ASSERT(kSymbolTag != 0);
+  STATIC_ASSERT(kSymbolTag != 0);
   __ tst(hash, Operand(kIsSymbolMask));
   __ b(eq, not_symbol);
 }
@@ -1333,7 +1333,7 @@
   __ cmp(key, Operand(ip));
   __ b(hs, &slow);
   // Calculate key + 1 as smi.
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   __ add(r4, key, Operand(Smi::FromInt(1)));
   __ str(r4, FieldMemOperand(receiver, JSArray::kLengthOffset));
   __ b(&fast);
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index b96805e..6292ff8 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1043,7 +1043,7 @@
         : instr->SecondSuccessor();
     return new LGoto(successor->block_id());
   }
-  return new LBranch(UseRegisterAtStart(v));
+  return AssignEnvironment(new LBranch(UseRegister(v)));
 }
 
 
@@ -1403,7 +1403,6 @@
 
 LInstruction* LChunkBuilder::DoCompareGeneric(HCompareGeneric* instr) {
   Token::Value op = instr->token();
-  Representation r = instr->GetInputRepresentation();
   ASSERT(instr->left()->representation().IsTagged());
   ASSERT(instr->right()->representation().IsTagged());
   bool reversed = (op == Token::GT || op == Token::LTE);
@@ -1513,16 +1512,10 @@
 }
 
 
-LInstruction* LChunkBuilder::DoExternalArrayLength(
-    HExternalArrayLength* instr) {
+LInstruction* LChunkBuilder::DoFixedArrayBaseLength(
+    HFixedArrayBaseLength* instr) {
   LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LExternalArrayLength(array));
-}
-
-
-LInstruction* LChunkBuilder::DoFixedArrayLength(HFixedArrayLength* instr) {
-  LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LFixedArrayLength(array));
+  return DefineAsRegister(new LFixedArrayBaseLength(array));
 }
 
 
@@ -2010,8 +2003,8 @@
 
 
 LInstruction* LChunkBuilder::DoStringCharCodeAt(HStringCharCodeAt* instr) {
-  LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegisterOrConstant(instr->index());
+  LOperand* string = UseTempRegister(instr->string());
+  LOperand* index = UseTempRegister(instr->index());
   LStringCharCodeAt* result = new LStringCharCodeAt(string, index);
   return AssignEnvironment(AssignPointerMap(DefineAsRegister(result)));
 }
diff --git a/src/arm/lithium-arm.h b/src/arm/lithium-arm.h
index b477e99..e14e6fc 100644
--- a/src/arm/lithium-arm.h
+++ b/src/arm/lithium-arm.h
@@ -92,8 +92,7 @@
   V(DivI)                                       \
   V(DoubleToI)                                  \
   V(ElementsKind)                               \
-  V(ExternalArrayLength)                        \
-  V(FixedArrayLength)                           \
+  V(FixedArrayBaseLength)                       \
   V(FunctionLiteral)                            \
   V(GetCachedArrayIndex)                        \
   V(GlobalObject)                               \
@@ -915,25 +914,15 @@
 };
 
 
-class LExternalArrayLength: public LTemplateInstruction<1, 1, 0> {
+class LFixedArrayBaseLength: public LTemplateInstruction<1, 1, 0> {
  public:
-  explicit LExternalArrayLength(LOperand* value) {
+  explicit LFixedArrayBaseLength(LOperand* value) {
     inputs_[0] = value;
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(ExternalArrayLength, "external-array-length")
-  DECLARE_HYDROGEN_ACCESSOR(ExternalArrayLength)
-};
-
-
-class LFixedArrayLength: public LTemplateInstruction<1, 1, 0> {
- public:
-  explicit LFixedArrayLength(LOperand* value) {
-    inputs_[0] = value;
-  }
-
-  DECLARE_CONCRETE_INSTRUCTION(FixedArrayLength, "fixed-array-length")
-  DECLARE_HYDROGEN_ACCESSOR(FixedArrayLength)
+  DECLARE_CONCRETE_INSTRUCTION(FixedArrayBaseLength,
+                               "fixed-array-base-length")
+  DECLARE_HYDROGEN_ACCESSOR(FixedArrayBaseLength)
 };
 
 
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index ad8091b..976576b 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -1378,17 +1378,10 @@
 }
 
 
-void LCodeGen::DoExternalArrayLength(LExternalArrayLength* instr) {
+void LCodeGen::DoFixedArrayBaseLength(LFixedArrayBaseLength* instr) {
   Register result = ToRegister(instr->result());
   Register array = ToRegister(instr->InputAt(0));
-  __ ldr(result, FieldMemOperand(array, ExternalArray::kLengthOffset));
-}
-
-
-void LCodeGen::DoFixedArrayLength(LFixedArrayLength* instr) {
-  Register result = ToRegister(instr->result());
-  Register array = ToRegister(instr->InputAt(0));
-  __ ldr(result, FieldMemOperand(array, FixedArray::kLengthOffset));
+  __ ldr(result, FieldMemOperand(array, FixedArrayBase::kLengthOffset));
 }
 
 
@@ -1564,52 +1557,96 @@
   } else {
     ASSERT(r.IsTagged());
     Register reg = ToRegister(instr->InputAt(0));
-    if (instr->hydrogen()->value()->type().IsBoolean()) {
-      __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-      __ cmp(reg, ip);
+    HType type = instr->hydrogen()->value()->type();
+    if (type.IsBoolean()) {
+      __ CompareRoot(reg, Heap::kTrueValueRootIndex);
       EmitBranch(true_block, false_block, eq);
+    } else if (type.IsSmi()) {
+      __ cmp(reg, Operand(0));
+      EmitBranch(true_block, false_block, ne);
     } else {
       Label* true_label = chunk_->GetAssemblyLabel(true_block);
       Label* false_label = chunk_->GetAssemblyLabel(false_block);
 
-      __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-      __ cmp(reg, ip);
-      __ b(eq, false_label);
-      __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-      __ cmp(reg, ip);
-      __ b(eq, true_label);
-      __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-      __ cmp(reg, ip);
-      __ b(eq, false_label);
-      __ cmp(reg, Operand(0));
-      __ b(eq, false_label);
-      __ JumpIfSmi(reg, true_label);
+      ToBooleanStub::Types expected = instr->hydrogen()->expected_input_types();
+      // Avoid deopts in the case where we've never executed this path before.
+      if (expected.IsEmpty()) expected = ToBooleanStub::all_types();
 
-      // Test double values. Zero and NaN are false.
-      Label call_stub;
-      DoubleRegister dbl_scratch = double_scratch0();
-      Register scratch = scratch0();
-      __ ldr(scratch, FieldMemOperand(reg, HeapObject::kMapOffset));
-      __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
-      __ cmp(scratch, Operand(ip));
-      __ b(ne, &call_stub);
-      __ sub(ip, reg, Operand(kHeapObjectTag));
-      __ vldr(dbl_scratch, ip, HeapNumber::kValueOffset);
-      __ VFPCompareAndLoadFlags(dbl_scratch, 0.0, scratch);
-      __ tst(scratch, Operand(kVFPZConditionFlagBit | kVFPVConditionFlagBit));
-      __ b(ne, false_label);
-      __ b(true_label);
+      if (expected.Contains(ToBooleanStub::UNDEFINED)) {
+        // undefined -> false.
+        __ CompareRoot(reg, Heap::kUndefinedValueRootIndex);
+        __ b(eq, false_label);
+      }
+      if (expected.Contains(ToBooleanStub::BOOLEAN)) {
+        // Boolean -> its value.
+        __ CompareRoot(reg, Heap::kTrueValueRootIndex);
+        __ b(eq, true_label);
+        __ CompareRoot(reg, Heap::kFalseValueRootIndex);
+        __ b(eq, false_label);
+      }
+      if (expected.Contains(ToBooleanStub::NULL_TYPE)) {
+        // 'null' -> false.
+        __ CompareRoot(reg, Heap::kNullValueRootIndex);
+        __ b(eq, false_label);
+      }
 
-      // The conversion stub doesn't cause garbage collections so it's
-      // safe to not record a safepoint after the call.
-      __ bind(&call_stub);
-      ToBooleanStub stub(reg);
-      RegList saved_regs = kJSCallerSaved | kCalleeSaved;
-      __ stm(db_w, sp, saved_regs);
-      __ CallStub(&stub);
-      __ cmp(reg, Operand(0));
-      __ ldm(ia_w, sp, saved_regs);
-      EmitBranch(true_block, false_block, ne);
+      if (expected.Contains(ToBooleanStub::SMI)) {
+        // Smis: 0 -> false, all other -> true.
+        __ cmp(reg, Operand(0));
+        __ b(eq, false_label);
+        __ JumpIfSmi(reg, true_label);
+      } else if (expected.NeedsMap()) {
+        // If we need a map later and have a Smi -> deopt.
+        __ tst(reg, Operand(kSmiTagMask));
+        DeoptimizeIf(eq, instr->environment());
+      }
+
+      const Register map = scratch0();
+      if (expected.NeedsMap()) {
+        __ ldr(map, FieldMemOperand(reg, HeapObject::kMapOffset));
+
+        if (expected.CanBeUndetectable()) {
+          // Undetectable -> false.
+          __ ldrb(ip, FieldMemOperand(map, Map::kBitFieldOffset));
+          __ tst(ip, Operand(1 << Map::kIsUndetectable));
+          __ b(ne, false_label);
+        }
+      }
+
+      if (expected.Contains(ToBooleanStub::SPEC_OBJECT)) {
+        // spec object -> true.
+        __ CompareInstanceType(map, ip, FIRST_SPEC_OBJECT_TYPE);
+        __ b(ge, true_label);
+      }
+
+      if (expected.Contains(ToBooleanStub::STRING)) {
+        // String value -> false iff empty.
+        Label not_string;
+        __ CompareInstanceType(map, ip, FIRST_NONSTRING_TYPE);
+        __ b(ge, &not_string);
+        __ ldr(ip, FieldMemOperand(reg, String::kLengthOffset));
+        __ cmp(ip, Operand(0));
+        __ b(ne, true_label);
+        __ b(false_label);
+        __ bind(&not_string);
+      }
+
+      if (expected.Contains(ToBooleanStub::HEAP_NUMBER)) {
+        // heap number -> false iff +0, -0, or NaN.
+        DoubleRegister dbl_scratch = double_scratch0();
+        Label not_heap_number;
+        __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
+        __ b(ne, &not_heap_number);
+        __ vldr(dbl_scratch, FieldMemOperand(reg, HeapNumber::kValueOffset));
+        __ VFPCompareAndSetFlags(dbl_scratch, 0.0);
+        __ b(vs, false_label);  // NaN -> false.
+        __ b(eq, false_label);  // +0, -0 -> false.
+        __ b(true_label);
+        __ bind(&not_heap_number);
+      }
+
+      // We've seen something for the first time -> deopt.
+      DeoptimizeIf(al, instr->environment());
     }
   }
 }
@@ -1767,7 +1804,6 @@
 void LCodeGen::DoIsObjectAndBranch(LIsObjectAndBranch* instr) {
   Register reg = ToRegister(instr->InputAt(0));
   Register temp1 = ToRegister(instr->TempAt(0));
-  Register temp2 = scratch0();
 
   int true_block = chunk_->LookupDestination(instr->true_block_id());
   int false_block = chunk_->LookupDestination(instr->false_block_id());
@@ -2722,7 +2758,6 @@
 
 
 void LCodeGen::DoGlobalObject(LGlobalObject* instr) {
-  Register context = ToRegister(instr->context());
   Register result = ToRegister(instr->result());
   __ ldr(result, ContextOperand(cp, Context::GLOBAL_INDEX));
 }
@@ -2928,19 +2963,18 @@
 void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
   DoubleRegister input = ToDoubleRegister(instr->InputAt(0));
   Register result = ToRegister(instr->result());
-  Register scratch1 = result;
-  Register scratch2 = scratch0();
+  Register scratch = scratch0();
   Label done, check_sign_on_zero;
 
   // Extract exponent bits.
-  __ vmov(scratch1, input.high());
-  __ ubfx(scratch2,
-          scratch1,
+  __ vmov(result, input.high());
+  __ ubfx(scratch,
+          result,
           HeapNumber::kExponentShift,
           HeapNumber::kExponentBits);
 
   // If the number is in ]-0.5, +0.5[, the result is +/- 0.
-  __ cmp(scratch2, Operand(HeapNumber::kExponentBias - 2));
+  __ cmp(scratch, Operand(HeapNumber::kExponentBias - 2));
   __ mov(result, Operand(0), LeaveCC, le);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     __ b(le, &check_sign_on_zero);
@@ -2950,19 +2984,19 @@
 
   // The following conversion will not work with numbers
   // outside of ]-2^32, 2^32[.
-  __ cmp(scratch2, Operand(HeapNumber::kExponentBias + 32));
+  __ cmp(scratch, Operand(HeapNumber::kExponentBias + 32));
   DeoptimizeIf(ge, instr->environment());
 
   // Save the original sign for later comparison.
-  __ and_(scratch2, scratch1, Operand(HeapNumber::kSignMask));
+  __ and_(scratch, result, Operand(HeapNumber::kSignMask));
 
   __ Vmov(double_scratch0(), 0.5);
   __ vadd(input, input, double_scratch0());
 
   // Check sign of the result: if the sign changed, the input
   // value was in ]0.5, 0[ and the result should be -0.
-  __ vmov(scratch1, input.high());
-  __ eor(scratch1, scratch1, Operand(scratch2), SetCC);
+  __ vmov(result, input.high());
+  __ eor(result, result, Operand(scratch), SetCC);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     DeoptimizeIf(mi, instr->environment());
   } else {
@@ -2973,8 +3007,8 @@
   __ EmitVFPTruncate(kRoundToMinusInf,
                      double_scratch0().low(),
                      input,
-                     scratch1,
-                     scratch2);
+                     result,
+                     scratch);
   DeoptimizeIf(ne, instr->environment());
   __ vmov(result, double_scratch0().low());
 
@@ -2983,8 +3017,8 @@
     __ cmp(result, Operand(0));
     __ b(ne, &done);
     __ bind(&check_sign_on_zero);
-    __ vmov(scratch1, input.high());
-    __ tst(scratch1, Operand(HeapNumber::kSignMask));
+    __ vmov(scratch, input.high());
+    __ tst(scratch, Operand(HeapNumber::kSignMask));
     DeoptimizeIf(ne, instr->environment());
   }
   __ bind(&done);
@@ -3421,97 +3455,81 @@
     LStringCharCodeAt* instr_;
   };
 
-  Register scratch = scratch0();
   Register string = ToRegister(instr->string());
-  Register index = no_reg;
-  int const_index = -1;
-  if (instr->index()->IsConstantOperand()) {
-    const_index = ToInteger32(LConstantOperand::cast(instr->index()));
-    STATIC_ASSERT(String::kMaxLength <= Smi::kMaxValue);
-    if (!Smi::IsValid(const_index)) {
-      // Guaranteed to be out of bounds because of the assert above.
-      // So the bounds check that must dominate this instruction must
-      // have deoptimized already.
-      if (FLAG_debug_code) {
-        __ Abort("StringCharCodeAt: out of bounds index.");
-      }
-      // No code needs to be generated.
-      return;
-    }
-  } else {
-    index = ToRegister(instr->index());
-  }
+  Register index = ToRegister(instr->index());
   Register result = ToRegister(instr->result());
 
   DeferredStringCharCodeAt* deferred =
       new DeferredStringCharCodeAt(this, instr);
 
-  Label flat_string, ascii_string, done;
-
   // Fetch the instance type of the receiver into result register.
   __ ldr(result, FieldMemOperand(string, HeapObject::kMapOffset));
   __ ldrb(result, FieldMemOperand(result, Map::kInstanceTypeOffset));
 
-  // We need special handling for non-flat strings.
-  STATIC_ASSERT(kSeqStringTag == 0);
-  __ tst(result, Operand(kStringRepresentationMask));
-  __ b(eq, &flat_string);
+  // We need special handling for indirect strings.
+  Label check_sequential;
+  __ tst(result, Operand(kIsIndirectStringMask));
+  __ b(eq, &check_sequential);
 
-  // Handle non-flat strings.
-  __ tst(result, Operand(kIsConsStringMask));
-  __ b(eq, deferred->entry());
+  // Dispatch on the indirect string shape: slice or cons.
+  Label cons_string;
+  __ tst(result, Operand(kSlicedNotConsMask));
+  __ b(eq, &cons_string);
 
-  // ConsString.
+  // Handle slices.
+  Label indirect_string_loaded;
+  __ ldr(result, FieldMemOperand(string, SlicedString::kOffsetOffset));
+  __ add(index, index, Operand(result, ASR, kSmiTagSize));
+  __ ldr(string, FieldMemOperand(string, SlicedString::kParentOffset));
+  __ jmp(&indirect_string_loaded);
+
+  // Handle conses.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
-  __ ldr(scratch, FieldMemOperand(string, ConsString::kSecondOffset));
+  __ bind(&cons_string);
+  __ ldr(result, FieldMemOperand(string, ConsString::kSecondOffset));
   __ LoadRoot(ip, Heap::kEmptyStringRootIndex);
-  __ cmp(scratch, ip);
+  __ cmp(result, ip);
   __ b(ne, deferred->entry());
   // Get the first of the two strings and load its instance type.
   __ ldr(string, FieldMemOperand(string, ConsString::kFirstOffset));
+
+  __ bind(&indirect_string_loaded);
   __ ldr(result, FieldMemOperand(string, HeapObject::kMapOffset));
   __ ldrb(result, FieldMemOperand(result, Map::kInstanceTypeOffset));
-  // If the first cons component is also non-flat, then go to runtime.
+
+  // Check whether the string is sequential. The only non-sequential
+  // shapes we support have just been unwrapped above.
+  __ bind(&check_sequential);
   STATIC_ASSERT(kSeqStringTag == 0);
   __ tst(result, Operand(kStringRepresentationMask));
   __ b(ne, deferred->entry());
 
-  // Check for 1-byte or 2-byte string.
-  __ bind(&flat_string);
+  // Dispatch on the encoding: ASCII or two-byte.
+  Label ascii_string;
   STATIC_ASSERT(kAsciiStringTag != 0);
   __ tst(result, Operand(kStringEncodingMask));
   __ b(ne, &ascii_string);
 
-  // 2-byte string.
-  // Load the 2-byte character code into the result register.
-  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
-  if (instr->index()->IsConstantOperand()) {
-    __ ldrh(result,
-            FieldMemOperand(string,
-                            SeqTwoByteString::kHeaderSize + 2 * const_index));
-  } else {
-    __ add(scratch,
-           string,
-           Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
-    __ ldrh(result, MemOperand(scratch, index, LSL, 1));
-  }
+  // Two-byte string.
+  // Load the two-byte character code into the result register.
+  Label done;
+  __ add(result,
+         string,
+         Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
+  __ ldrh(result, MemOperand(result, index, LSL, 1));
   __ jmp(&done);
 
   // ASCII string.
   // Load the byte into the result register.
   __ bind(&ascii_string);
-  if (instr->index()->IsConstantOperand()) {
-    __ ldrb(result, FieldMemOperand(string,
-                                    SeqAsciiString::kHeaderSize + const_index));
-  } else {
-    __ add(scratch,
-           string,
-           Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
-    __ ldrb(result, MemOperand(scratch, index));
-  }
+  __ add(result,
+         string,
+         Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ ldrb(result, MemOperand(result, index));
+
   __ bind(&done);
   __ bind(deferred->exit());
 }
@@ -3739,7 +3757,7 @@
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister() && input->Equals(instr->result()));
   if (instr->needs_check()) {
-    ASSERT(kHeapObjectTag == 1);
+    STATIC_ASSERT(kHeapObjectTag == 1);
     // If the input is a HeapObject, SmiUntag will set the carry flag.
     __ SmiUntag(ToRegister(input), SetCC);
     DeoptimizeIf(cs, instr->environment());
@@ -3824,7 +3842,7 @@
   // The input was optimistically untagged; revert it.
   // The carry flag is set when we reach this deferred code as we just executed
   // SmiUntag(heap_object, SetCC)
-  ASSERT(kHeapObjectTag == 1);
+  STATIC_ASSERT(kHeapObjectTag == 1);
   __ adc(input_reg, input_reg, Operand(input_reg));
 
   // Heap number map check.
@@ -3929,7 +3947,6 @@
   Register scratch1 = scratch0();
   Register scratch2 = ToRegister(instr->TempAt(0));
   DwVfpRegister double_input = ToDoubleRegister(instr->InputAt(0));
-  DwVfpRegister double_scratch = double_scratch0();
   SwVfpRegister single_scratch = double_scratch0().low();
 
   Label done;
@@ -4070,7 +4087,7 @@
   // conversions.
   __ cmp(input_reg, Operand(factory()->undefined_value()));
   DeoptimizeIf(ne, instr->environment());
-  __ movt(input_reg, 0);
+  __ mov(result_reg, Operand(0));
   __ jmp(&done);
 
   // Heap number
@@ -4309,6 +4326,10 @@
     __ CompareRoot(input, Heap::kFalseValueRootIndex);
     final_branch_condition = eq;
 
+  } else if (FLAG_harmony_typeof && type_name->Equals(heap()->null_symbol())) {
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
+    final_branch_condition = eq;
+
   } else if (type_name->Equals(heap()->undefined_symbol())) {
     __ CompareRoot(input, Heap::kUndefinedValueRootIndex);
     __ b(eq, true_label);
@@ -4327,8 +4348,10 @@
 
   } else if (type_name->Equals(heap()->object_symbol())) {
     __ JumpIfSmi(input, false_label);
-    __ CompareRoot(input, Heap::kNullValueRootIndex);
-    __ b(eq, true_label);
+    if (!FLAG_harmony_typeof) {
+      __ CompareRoot(input, Heap::kNullValueRootIndex);
+      __ b(eq, true_label);
+    }
     __ CompareObjectType(input, input, scratch,
                          FIRST_NONCALLABLE_SPEC_OBJECT_TYPE);
     __ b(lt, false_label);
diff --git a/src/arm/lithium-gap-resolver-arm.cc b/src/arm/lithium-gap-resolver-arm.cc
index 02608a6..26f60fa 100644
--- a/src/arm/lithium-gap-resolver-arm.cc
+++ b/src/arm/lithium-gap-resolver-arm.cc
@@ -254,7 +254,6 @@
     } else {
       ASSERT(destination->IsStackSlot());
       ASSERT(!in_cycle_);  // Constant moves happen after all cycles are gone.
-      MemOperand destination_operand = cgen_->ToMemOperand(destination);
       __ mov(kSavedValueRegister, source_operand);
       __ str(kSavedValueRegister, cgen_->ToMemOperand(destination));
     }
@@ -265,8 +264,7 @@
       __ vmov(cgen_->ToDoubleRegister(destination), source_register);
     } else {
       ASSERT(destination->IsDoubleStackSlot());
-      MemOperand destination_operand = cgen_->ToMemOperand(destination);
-      __ vstr(source_register, destination_operand);
+      __ vstr(source_register, cgen_->ToMemOperand(destination));
     }
 
   } else if (source->IsDoubleStackSlot()) {
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index c34a579..88477bb 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -1102,7 +1102,13 @@
 void MacroAssembler::PushTryHandler(CodeLocation try_location,
                                     HandlerType type) {
   // Adjust this code if not the case.
-  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
+
   // The pc (return address) is passed in register lr.
   if (try_location == IN_JAVASCRIPT) {
     if (type == TRY_CATCH_HANDLER) {
@@ -1110,14 +1116,10 @@
     } else {
       mov(r3, Operand(StackHandler::TRY_FINALLY));
     }
-    ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize
-           && StackHandlerConstants::kFPOffset == 2 * kPointerSize
-           && StackHandlerConstants::kPCOffset == 3 * kPointerSize);
-    stm(db_w, sp, r3.bit() | fp.bit() | lr.bit());
+    stm(db_w, sp, r3.bit() | cp.bit() | fp.bit() | lr.bit());
     // Save the current handler as the next handler.
     mov(r3, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
     ldr(r1, MemOperand(r3));
-    ASSERT(StackHandlerConstants::kNextOffset == 0);
     push(r1);
     // Link this handler as the new current one.
     str(sp, MemOperand(r3));
@@ -1127,16 +1129,13 @@
     // The frame pointer does not point to a JS frame so we save NULL
     // for fp. We expect the code throwing an exception to check fp
     // before dereferencing it to restore the context.
-    mov(ip, Operand(0, RelocInfo::NONE));  // To save a NULL frame pointer.
-    mov(r6, Operand(StackHandler::ENTRY));
-    ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize
-           && StackHandlerConstants::kFPOffset == 2 * kPointerSize
-           && StackHandlerConstants::kPCOffset == 3 * kPointerSize);
-    stm(db_w, sp, r6.bit() | ip.bit() | lr.bit());
+    mov(r5, Operand(StackHandler::ENTRY));  // State.
+    mov(r6, Operand(Smi::FromInt(0)));  // Indicates no context.
+    mov(r7, Operand(0, RelocInfo::NONE));  // NULL frame pointer.
+    stm(db_w, sp, r5.bit() | r6.bit() | r7.bit() | lr.bit());
     // Save the current handler as the next handler.
     mov(r7, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
     ldr(r6, MemOperand(r7));
-    ASSERT(StackHandlerConstants::kNextOffset == 0);
     push(r6);
     // Link this handler as the new current one.
     str(sp, MemOperand(r7));
@@ -1145,7 +1144,7 @@
 
 
 void MacroAssembler::PopTryHandler() {
-  ASSERT_EQ(0, StackHandlerConstants::kNextOffset);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(r1);
   mov(ip, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
   add(sp, sp, Operand(StackHandlerConstants::kSize - kPointerSize));
@@ -1154,39 +1153,40 @@
 
 
 void MacroAssembler::Throw(Register value) {
+  // Adjust this code if not the case.
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // r0 is expected to hold the exception.
   if (!value.is(r0)) {
     mov(r0, value);
   }
 
-  // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
-
   // Drop the sp to the top of the handler.
   mov(r3, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
   ldr(sp, MemOperand(r3));
 
-  // Restore the next handler and frame pointer, discard handler state.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  // Restore the next handler.
   pop(r2);
   str(r2, MemOperand(r3));
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
-  ldm(ia_w, sp, r3.bit() | fp.bit());  // r3: discarded state.
 
-  // Before returning we restore the context from the frame pointer if
-  // not NULL.  The frame pointer is NULL in the exception handler of a
-  // JS entry frame.
-  cmp(fp, Operand(0, RelocInfo::NONE));
-  // Set cp to NULL if fp is NULL.
-  mov(cp, Operand(0, RelocInfo::NONE), LeaveCC, eq);
-  // Restore cp otherwise.
-  ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset), ne);
+  // Restore context and frame pointer, discard state (r3).
+  ldm(ia_w, sp, r3.bit() | cp.bit() | fp.bit());
+
+  // If the handler is a JS frame, restore the context to the frame.
+  // (r3 == ENTRY) == (fp == 0) == (cp == 0), so we could test any
+  // of them.
+  cmp(r3, Operand(StackHandler::ENTRY));
+  str(cp, MemOperand(fp, StandardFrameConstants::kContextOffset), ne);
+
 #ifdef DEBUG
   if (emit_debug_code()) {
     mov(lr, Operand(pc));
   }
 #endif
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   pop(pc);
 }
 
@@ -1194,8 +1194,12 @@
 void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
                                       Register value) {
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
-
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // r0 is expected to hold the exception.
   if (!value.is(r0)) {
     mov(r0, value);
@@ -1220,7 +1224,6 @@
   bind(&done);
 
   // Set the top handler address to next handler past the current ENTRY handler.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(r2);
   str(r2, MemOperand(r3));
 
@@ -1242,26 +1245,17 @@
 
   // Stack layout at this point. See also StackHandlerConstants.
   // sp ->   state (ENTRY)
+  //         cp
   //         fp
   //         lr
 
-  // Discard handler state (r2 is not used) and restore frame pointer.
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
-  ldm(ia_w, sp, r2.bit() | fp.bit());  // r2: discarded state.
-  // Before returning we restore the context from the frame pointer if
-  // not NULL.  The frame pointer is NULL in the exception handler of a
-  // JS entry frame.
-  cmp(fp, Operand(0, RelocInfo::NONE));
-  // Set cp to NULL if fp is NULL.
-  mov(cp, Operand(0, RelocInfo::NONE), LeaveCC, eq);
-  // Restore cp otherwise.
-  ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset), ne);
+  // Restore context and frame pointer, discard state (r2).
+  ldm(ia_w, sp, r2.bit() | cp.bit() | fp.bit());
 #ifdef DEBUG
   if (emit_debug_code()) {
     mov(lr, Operand(pc));
   }
 #endif
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   pop(pc);
 }
 
diff --git a/src/arm/regexp-macro-assembler-arm.cc b/src/arm/regexp-macro-assembler-arm.cc
index 983a528..cd76edb 100644
--- a/src/arm/regexp-macro-assembler-arm.cc
+++ b/src/arm/regexp-macro-assembler-arm.cc
@@ -1034,12 +1034,13 @@
   }
 
   // Prepare for possible GC.
-  HandleScope handles;
+  HandleScope handles(isolate);
   Handle<Code> code_handle(re_code);
 
   Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
+
   // Current string.
-  bool is_ascii = subject->IsAsciiRepresentation();
+  bool is_ascii = subject->IsAsciiRepresentationUnderneath();
 
   ASSERT(re_code->instruction_start() <= *return_address);
   ASSERT(*return_address <=
@@ -1048,7 +1049,7 @@
   MaybeObject* result = Execution::HandleStackGuardInterrupt();
 
   if (*code_handle != re_code) {  // Return address no longer valid
-    int delta = *code_handle - re_code;
+    int delta = code_handle->address() - re_code->address();
     // Overwrite the return address on the stack.
     *return_address += delta;
   }
@@ -1057,8 +1058,20 @@
     return EXCEPTION;
   }
 
+  Handle<String> subject_tmp = subject;
+  int slice_offset = 0;
+
+  // Extract the underlying string and the slice offset.
+  if (StringShape(*subject_tmp).IsCons()) {
+    subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
+  } else if (StringShape(*subject_tmp).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(*subject_tmp);
+    subject_tmp = Handle<String>(slice->parent());
+    slice_offset = slice->offset();
+  }
+
   // String might have changed.
-  if (subject->IsAsciiRepresentation() != is_ascii) {
+  if (subject_tmp->IsAsciiRepresentation() != is_ascii) {
     // If we changed between an ASCII and an UC16 string, the specialized
     // code cannot be used, and we need to restart regexp matching from
     // scratch (including, potentially, compiling a new version of the code).
@@ -1069,8 +1082,8 @@
   // be a sequential or external string with the same content.
   // Update the start and end pointers in the stack frame to the current
   // location (whether it has actually moved or not).
-  ASSERT(StringShape(*subject).IsSequential() ||
-      StringShape(*subject).IsExternal());
+  ASSERT(StringShape(*subject_tmp).IsSequential() ||
+      StringShape(*subject_tmp).IsExternal());
 
   // The original start address of the characters to match.
   const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);
@@ -1078,13 +1091,14 @@
   // Find the current start address of the same character at the current string
   // position.
   int start_index = frame_entry<int>(re_frame, kStartIndex);
-  const byte* new_address = StringCharacterPosition(*subject, start_index);
+  const byte* new_address = StringCharacterPosition(*subject_tmp,
+                                                    start_index + slice_offset);
 
   if (start_address != new_address) {
     // If there is a difference, update the object pointer and start and end
     // addresses in the RegExp stack frame to match the new value.
     const byte* end_address = frame_entry<const byte* >(re_frame, kInputEnd);
-    int byte_length = end_address - start_address;
+    int byte_length = static_cast<int>(end_address - start_address);
     frame_entry<const String*>(re_frame, kInputString) = *subject;
     frame_entry<const byte*>(re_frame, kInputStart) = new_address;
     frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
diff --git a/src/arm/stub-cache-arm.cc b/src/arm/stub-cache-arm.cc
index c2665f8..5345892 100644
--- a/src/arm/stub-cache-arm.cc
+++ b/src/arm/stub-cache-arm.cc
@@ -1183,9 +1183,8 @@
   __ JumpIfSmi(receiver, miss);
 
   // Check that the maps haven't changed.
-  Register reg =
-      CheckPrototypes(object, receiver, holder,
-                      scratch1, scratch2, scratch3, name, miss);
+  CheckPrototypes(object, receiver, holder, scratch1, scratch2, scratch3, name,
+                  miss);
 
   // Return the constant value.
   __ mov(r0, Operand(Handle<Object>(value)));
@@ -3489,16 +3488,16 @@
 
   // Check that the index is in range.
   __ ldr(ip, FieldMemOperand(r3, ExternalArray::kLengthOffset));
-  __ cmp(ip, Operand(key, ASR, kSmiTagSize));
+  __ cmp(key, ip);
   // Unsigned comparison catches both negative and too-large values.
-  __ b(lo, &miss_force_generic);
+  __ b(hs, &miss_force_generic);
 
   __ ldr(r3, FieldMemOperand(r3, ExternalArray::kExternalPointerOffset));
   // r3: base pointer of external storage
 
   // We are not untagging smi key and instead work with it
   // as if it was premultiplied by 2.
-  ASSERT((kSmiTag == 0) && (kSmiTagSize == 1));
+  STATIC_ASSERT((kSmiTag == 0) && (kSmiTagSize == 1));
 
   Register value = r2;
   switch (elements_kind) {
@@ -3811,22 +3810,20 @@
   // This stub is meant to be tail-jumped to, the receiver must already
   // have been verified by the caller to not be a smi.
 
-  __ ldr(r3, FieldMemOperand(receiver, JSObject::kElementsOffset));
-
   // Check that the key is a smi.
   __ JumpIfNotSmi(key, &miss_force_generic);
 
+  __ ldr(r3, FieldMemOperand(receiver, JSObject::kElementsOffset));
+
   // Check that the index is in range
-  __ SmiUntag(r4, key);
   __ ldr(ip, FieldMemOperand(r3, ExternalArray::kLengthOffset));
-  __ cmp(r4, ip);
+  __ cmp(key, ip);
   // Unsigned comparison catches both negative and too-large values.
   __ b(hs, &miss_force_generic);
 
   // Handle both smis and HeapNumbers in the fast path. Go to the
   // runtime for all other kinds of values.
   // r3: external array.
-  // r4: key (integer).
   if (elements_kind == JSObject::EXTERNAL_PIXEL_ELEMENTS) {
     // Double to pixel conversion is only implemented in the runtime for now.
     __ JumpIfNotSmi(value, &slow);
@@ -3837,32 +3834,32 @@
   __ ldr(r3, FieldMemOperand(r3, ExternalArray::kExternalPointerOffset));
 
   // r3: base pointer of external storage.
-  // r4: key (integer).
   // r5: value (integer).
   switch (elements_kind) {
     case JSObject::EXTERNAL_PIXEL_ELEMENTS:
       // Clamp the value to [0..255].
       __ Usat(r5, 8, Operand(r5));
-      __ strb(r5, MemOperand(r3, r4, LSL, 0));
+      __ strb(r5, MemOperand(r3, key, LSR, 1));
       break;
     case JSObject::EXTERNAL_BYTE_ELEMENTS:
     case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-      __ strb(r5, MemOperand(r3, r4, LSL, 0));
+      __ strb(r5, MemOperand(r3, key, LSR, 1));
       break;
     case JSObject::EXTERNAL_SHORT_ELEMENTS:
     case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-      __ strh(r5, MemOperand(r3, r4, LSL, 1));
+      __ strh(r5, MemOperand(r3, key, LSL, 0));
       break;
     case JSObject::EXTERNAL_INT_ELEMENTS:
     case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
-      __ str(r5, MemOperand(r3, r4, LSL, 2));
+      __ str(r5, MemOperand(r3, key, LSL, 1));
       break;
     case JSObject::EXTERNAL_FLOAT_ELEMENTS:
       // Perform int-to-float conversion and store to memory.
+      __ SmiUntag(r4, key);
       StoreIntAsFloat(masm, r3, r4, r5, r6, r7, r9);
       break;
     case JSObject::EXTERNAL_DOUBLE_ELEMENTS:
-      __ add(r3, r3, Operand(r4, LSL, 3));
+      __ add(r3, r3, Operand(key, LSL, 2));
       // r3: effective address of the double element
       FloatingPointHelper::Destination destination;
       if (CpuFeatures::IsSupported(VFP3)) {
@@ -3895,7 +3892,6 @@
 
   if (elements_kind != JSObject::EXTERNAL_PIXEL_ELEMENTS) {
     // r3: external array.
-    // r4: index (integer).
     __ bind(&check_heap_number);
     __ CompareObjectType(value, r5, r6, HEAP_NUMBER_TYPE);
     __ b(ne, &slow);
@@ -3903,7 +3899,6 @@
     __ ldr(r3, FieldMemOperand(r3, ExternalArray::kExternalPointerOffset));
 
     // r3: base pointer of external storage.
-    // r4: key (integer).
 
     // The WebGL specification leaves the behavior of storing NaN and
     // +/-Infinity into integer arrays basically undefined. For more
@@ -3916,13 +3911,13 @@
         // include -kHeapObjectTag into it.
         __ sub(r5, r0, Operand(kHeapObjectTag));
         __ vldr(d0, r5, HeapNumber::kValueOffset);
-        __ add(r5, r3, Operand(r4, LSL, 2));
+        __ add(r5, r3, Operand(key, LSL, 1));
         __ vcvt_f32_f64(s0, d0);
         __ vstr(s0, r5, 0);
       } else if (elements_kind == JSObject::EXTERNAL_DOUBLE_ELEMENTS) {
         __ sub(r5, r0, Operand(kHeapObjectTag));
         __ vldr(d0, r5, HeapNumber::kValueOffset);
-        __ add(r5, r3, Operand(r4, LSL, 3));
+        __ add(r5, r3, Operand(key, LSL, 2));
         __ vstr(d0, r5, 0);
       } else {
         // Hoisted load.  vldr requires offset to be a multiple of 4 so we can
@@ -3934,15 +3929,15 @@
         switch (elements_kind) {
           case JSObject::EXTERNAL_BYTE_ELEMENTS:
           case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-            __ strb(r5, MemOperand(r3, r4, LSL, 0));
+            __ strb(r5, MemOperand(r3, key, LSR, 1));
             break;
           case JSObject::EXTERNAL_SHORT_ELEMENTS:
           case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-            __ strh(r5, MemOperand(r3, r4, LSL, 1));
+            __ strh(r5, MemOperand(r3, key, LSL, 0));
             break;
           case JSObject::EXTERNAL_INT_ELEMENTS:
           case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
-            __ str(r5, MemOperand(r3, r4, LSL, 2));
+            __ str(r5, MemOperand(r3, key, LSL, 1));
             break;
           case JSObject::EXTERNAL_PIXEL_ELEMENTS:
           case JSObject::EXTERNAL_FLOAT_ELEMENTS:
@@ -4004,7 +3999,7 @@
         __ orr(r5, r7, Operand(r9, LSL, kBinary32ExponentShift));
 
         __ bind(&done);
-        __ str(r5, MemOperand(r3, r4, LSL, 2));
+        __ str(r5, MemOperand(r3, key, LSL, 1));
         // Entry registers are intact, r0 holds the value which is the return
         // value.
         __ Ret();
@@ -4017,7 +4012,7 @@
         __ orr(r5, r9, Operand(r6, LSR, kMantissaInLoWordShift));
         __ b(&done);
       } else if (elements_kind == JSObject::EXTERNAL_DOUBLE_ELEMENTS) {
-        __ add(r7, r3, Operand(r4, LSL, 3));
+        __ add(r7, r3, Operand(key, LSL, 2));
         // r7: effective address of destination element.
         __ str(r6, MemOperand(r7, 0));
         __ str(r5, MemOperand(r7, Register::kSizeInBytes));
@@ -4073,15 +4068,15 @@
         switch (elements_kind) {
           case JSObject::EXTERNAL_BYTE_ELEMENTS:
           case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-            __ strb(r5, MemOperand(r3, r4, LSL, 0));
+            __ strb(r5, MemOperand(r3, key, LSR, 1));
             break;
           case JSObject::EXTERNAL_SHORT_ELEMENTS:
           case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-            __ strh(r5, MemOperand(r3, r4, LSL, 1));
+            __ strh(r5, MemOperand(r3, key, LSL, 0));
             break;
           case JSObject::EXTERNAL_INT_ELEMENTS:
           case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
-            __ str(r5, MemOperand(r3, r4, LSL, 2));
+            __ str(r5, MemOperand(r3, key, LSL, 1));
             break;
           case JSObject::EXTERNAL_PIXEL_ELEMENTS:
           case JSObject::EXTERNAL_FLOAT_ELEMENTS:
@@ -4152,7 +4147,7 @@
 
   // Load the result and make sure it's not the hole.
   __ add(r3, r2, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
-  ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
   __ ldr(r4,
          MemOperand(r3, r0, LSL, kPointerSizeLog2 - kSmiTagSize));
   __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
@@ -4284,7 +4279,7 @@
 
   __ add(scratch,
          elements_reg, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
-  ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize < kPointerSizeLog2);
   __ str(value_reg,
          MemOperand(scratch, key_reg, LSL, kPointerSizeLog2 - kSmiTagSize));
   __ RecordWrite(scratch,
@@ -4399,11 +4394,18 @@
   } else {
     destination = FloatingPointHelper::kCoreRegisters;
   }
-  __ SmiUntag(value_reg, value_reg);
+
+  Register untagged_value = receiver_reg;
+  __ SmiUntag(untagged_value, value_reg);
   FloatingPointHelper::ConvertIntToDouble(
-      masm, value_reg, destination,
-      d0, mantissa_reg, exponent_reg,  // These are: double_dst, dst1, dst2.
-      scratch4, s2);  // These are: scratch2, single_scratch.
+      masm,
+      untagged_value,
+      destination,
+      d0,
+      mantissa_reg,
+      exponent_reg,
+      scratch4,
+      s2);
   if (destination == FloatingPointHelper::kVFPRegisters) {
     CpuFeatures::Scope scope(VFP3);
     __ vstr(d0, scratch, 0);
diff --git a/src/array.js b/src/array.js
index e6c13d9..f73b0c1 100644
--- a/src/array.js
+++ b/src/array.js
@@ -172,12 +172,12 @@
     } else {
       for (var i = 0; i < length; i++) {
         var e = array[i];
-          if (IS_NUMBER(e)) {
-            e = %_NumberToString(e);
-          } else if (!IS_STRING(e)) {
-            e = convert(e);
-          }
-          elements[i] = e;
+        if (IS_NUMBER(e)) {
+          e = %_NumberToString(e);
+        } else if (!IS_STRING(e)) {
+          e = convert(e);
+        }
+        elements[i] = e;
       }
     }
     var result = %_FastAsciiArrayJoin(elements, separator);
@@ -742,8 +742,7 @@
       else return x < y ? -1 : 1;
     };
   }
-  var receiver =
-      %_IsNativeOrStrictMode(comparefn) ? void 0 : %GetGlobalReceiver();
+  var receiver = %GetDefaultReceiver(comparefn);
 
   function InsertionSort(a, from, to) {
     for (var i = from + 1; i < to; i++) {
@@ -997,6 +996,9 @@
   if (!IS_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [ f ]);
   }
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  }
   // Pull out the length so that modifications to the length in the
   // loop will not affect the looping.
   var length = ToUint32(this.length);
@@ -1005,7 +1007,7 @@
   for (var i = 0; i < length; i++) {
     var current = this[i];
     if (!IS_UNDEFINED(current) || i in this) {
-      if (f.call(receiver, current, i, this)) {
+      if (%_CallFunction(receiver, current, i, this, f)) {
         result[result_length++] = current;
       }
     }
@@ -1023,13 +1025,16 @@
   if (!IS_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [ f ]);
   }
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  }
   // Pull out the length so that modifications to the length in the
   // loop will not affect the looping.
   var length =  TO_UINT32(this.length);
   for (var i = 0; i < length; i++) {
     var current = this[i];
     if (!IS_UNDEFINED(current) || i in this) {
-      f.call(receiver, current, i, this);
+      %_CallFunction(receiver, current, i, this, f);
     }
   }
 }
@@ -1046,13 +1051,16 @@
   if (!IS_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [ f ]);
   }
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  }
   // Pull out the length so that modifications to the length in the
   // loop will not affect the looping.
   var length = TO_UINT32(this.length);
   for (var i = 0; i < length; i++) {
     var current = this[i];
     if (!IS_UNDEFINED(current) || i in this) {
-      if (f.call(receiver, current, i, this)) return true;
+      if (%_CallFunction(receiver, current, i, this, f)) return true;
     }
   }
   return false;
@@ -1068,13 +1076,16 @@
   if (!IS_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [ f ]);
   }
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  }
   // Pull out the length so that modifications to the length in the
   // loop will not affect the looping.
   var length = TO_UINT32(this.length);
   for (var i = 0; i < length; i++) {
     var current = this[i];
     if (!IS_UNDEFINED(current) || i in this) {
-      if (!f.call(receiver, current, i, this)) return false;
+      if (!%_CallFunction(receiver, current, i, this, f)) return false;
     }
   }
   return true;
@@ -1089,6 +1100,9 @@
   if (!IS_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [ f ]);
   }
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  }
   // Pull out the length so that modifications to the length in the
   // loop will not affect the looping.
   var length = TO_UINT32(this.length);
@@ -1097,7 +1111,7 @@
   for (var i = 0; i < length; i++) {
     var current = this[i];
     if (!IS_UNDEFINED(current) || i in this) {
-      accumulator[i] = f.call(receiver, current, i, this);
+      accumulator[i] = %_CallFunction(receiver, current, i, this, f);
     }
   }
   %MoveArrayContents(accumulator, result);
@@ -1234,6 +1248,7 @@
   if (!IS_FUNCTION(callback)) {
     throw MakeTypeError('called_non_callable', [callback]);
   }
+
   // Pull out the length so that modifications to the length in the
   // loop will not affect the looping.
   var length = ToUint32(this.length);
@@ -1250,10 +1265,11 @@
     throw MakeTypeError('reduce_no_initial', []);
   }
 
+  var receiver = %GetDefaultReceiver(callback);
   for (; i < length; i++) {
     var element = this[i];
     if (!IS_UNDEFINED(element) || i in this) {
-      current = callback.call(void 0, current, element, i, this);
+      current = %_CallFunction(receiver, current, element, i, this, callback);
     }
   }
   return current;
@@ -1281,10 +1297,11 @@
     throw MakeTypeError('reduce_no_initial', []);
   }
 
+  var receiver = %GetDefaultReceiver(callback);
   for (; i >= 0; i--) {
     var element = this[i];
     if (!IS_UNDEFINED(element) || i in this) {
-      current = callback.call(void 0, current, element, i, this);
+      current = %_CallFunction(receiver, current, element, i, this, callback);
     }
   }
   return current;
diff --git a/src/assembler.cc b/src/assembler.cc
index fbd8089..ad5f350 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -74,7 +74,7 @@
 const double DoubleConstant::canonical_non_hole_nan = OS::nan_value();
 const double DoubleConstant::the_hole_nan = BitCast<double>(kHoleNanInt64);
 const double DoubleConstant::negative_infinity = -V8_INFINITY;
-const char* RelocInfo::kFillerCommentString = "DEOPTIMIZATION PADDING";
+const char* const RelocInfo::kFillerCommentString = "DEOPTIMIZATION PADDING";
 
 // -----------------------------------------------------------------------------
 // Implementation of AssemblerBase
diff --git a/src/assembler.h b/src/assembler.h
index 2d14f06..d58034d 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -171,7 +171,7 @@
   // where we are not sure to have enough space for patching in during
   // lazy deoptimization. This is the case if we have indirect calls for which
   // we do not normally record relocation info.
-  static const char* kFillerCommentString;
+  static const char* const kFillerCommentString;
 
   // The minimum size of a comment is equal to three bytes for the extra tagged
   // pc + the tag for the data, and kPointerSize for the actual pointer to the
diff --git a/src/ast-inl.h b/src/ast-inl.h
index c750e6b..731ad2f 100644
--- a/src/ast-inl.h
+++ b/src/ast-inl.h
@@ -50,7 +50,8 @@
              bool is_initializer_block)
     : BreakableStatement(isolate, labels, TARGET_FOR_NAMED_ONLY),
       statements_(capacity),
-      is_initializer_block_(is_initializer_block) {
+      is_initializer_block_(is_initializer_block),
+      block_scope_(NULL) {
 }
 
 
diff --git a/src/ast.cc b/src/ast.cc
index 2df62ee..7319abe 100644
--- a/src/ast.cc
+++ b/src/ast.cc
@@ -139,8 +139,7 @@
       assignment_id_(GetNextId(isolate)),
       block_start_(false),
       block_end_(false),
-      is_monomorphic_(false),
-      receiver_types_(NULL) {
+      is_monomorphic_(false) {
   ASSERT(Token::IsAssignmentOp(op));
   if (is_compound()) {
     binary_operation_ =
@@ -426,7 +425,7 @@
 }
 
 
-bool EnterWithContextStatement::IsInlineable() const {
+bool WithStatement::IsInlineable() const {
   return false;
 }
 
@@ -652,6 +651,7 @@
 void Property::RecordTypeFeedback(TypeFeedbackOracle* oracle) {
   // Record type feedback from the oracle in the AST.
   is_monomorphic_ = oracle->LoadIsMonomorphicNormal(this);
+  receiver_types_.Clear();
   if (key()->IsPropertyName()) {
     if (oracle->LoadIsBuiltin(this, Builtins::kLoadIC_ArrayLength)) {
       is_array_length_ = true;
@@ -664,16 +664,15 @@
       Literal* lit_key = key()->AsLiteral();
       ASSERT(lit_key != NULL && lit_key->handle()->IsString());
       Handle<String> name = Handle<String>::cast(lit_key->handle());
-      ZoneMapList* types = oracle->LoadReceiverTypes(this, name);
-      receiver_types_ = types;
+      oracle->LoadReceiverTypes(this, name, &receiver_types_);
     }
   } else if (oracle->LoadIsBuiltin(this, Builtins::kKeyedLoadIC_String)) {
     is_string_access_ = true;
   } else if (is_monomorphic_) {
-    monomorphic_receiver_type_ = oracle->LoadMonomorphicReceiverType(this);
+    receiver_types_.Add(oracle->LoadMonomorphicReceiverType(this));
   } else if (oracle->LoadIsMegamorphicWithTypeInfo(this)) {
-    receiver_types_ = new ZoneMapList(kMaxKeyedPolymorphism);
-    oracle->CollectKeyedReceiverTypes(this->id(), receiver_types_);
+    receiver_types_.Reserve(kMaxKeyedPolymorphism);
+    oracle->CollectKeyedReceiverTypes(this->id(), &receiver_types_);
   }
 }
 
@@ -682,30 +681,31 @@
   Property* prop = target()->AsProperty();
   ASSERT(prop != NULL);
   is_monomorphic_ = oracle->StoreIsMonomorphicNormal(this);
+  receiver_types_.Clear();
   if (prop->key()->IsPropertyName()) {
     Literal* lit_key = prop->key()->AsLiteral();
     ASSERT(lit_key != NULL && lit_key->handle()->IsString());
     Handle<String> name = Handle<String>::cast(lit_key->handle());
-    ZoneMapList* types = oracle->StoreReceiverTypes(this, name);
-    receiver_types_ = types;
+    oracle->StoreReceiverTypes(this, name, &receiver_types_);
   } else if (is_monomorphic_) {
     // Record receiver type for monomorphic keyed stores.
-    monomorphic_receiver_type_ = oracle->StoreMonomorphicReceiverType(this);
+    receiver_types_.Add(oracle->StoreMonomorphicReceiverType(this));
   } else if (oracle->StoreIsMegamorphicWithTypeInfo(this)) {
-    receiver_types_ = new ZoneMapList(kMaxKeyedPolymorphism);
-    oracle->CollectKeyedReceiverTypes(this->id(), receiver_types_);
+    receiver_types_.Reserve(kMaxKeyedPolymorphism);
+    oracle->CollectKeyedReceiverTypes(this->id(), &receiver_types_);
   }
 }
 
 
 void CountOperation::RecordTypeFeedback(TypeFeedbackOracle* oracle) {
   is_monomorphic_ = oracle->StoreIsMonomorphicNormal(this);
+  receiver_types_.Clear();
   if (is_monomorphic_) {
     // Record receiver type for monomorphic keyed stores.
-    monomorphic_receiver_type_ = oracle->StoreMonomorphicReceiverType(this);
+    receiver_types_.Add(oracle->StoreMonomorphicReceiverType(this));
   } else if (oracle->StoreIsMegamorphicWithTypeInfo(this)) {
-    receiver_types_ = new ZoneMapList(kMaxKeyedPolymorphism);
-    oracle->CollectKeyedReceiverTypes(this->id(), receiver_types_);
+    receiver_types_.Reserve(kMaxKeyedPolymorphism);
+    oracle->CollectKeyedReceiverTypes(this->id(), &receiver_types_);
   }
 }
 
@@ -789,15 +789,14 @@
   Literal* key = property->key()->AsLiteral();
   ASSERT(key != NULL && key->handle()->IsString());
   Handle<String> name = Handle<String>::cast(key->handle());
-  receiver_types_ = oracle->CallReceiverTypes(this, name, call_kind);
+  receiver_types_.Clear();
+  oracle->CallReceiverTypes(this, name, call_kind, &receiver_types_);
 #ifdef DEBUG
   if (FLAG_enable_slow_asserts) {
-    if (receiver_types_ != NULL) {
-      int length = receiver_types_->length();
-      for (int i = 0; i < length; i++) {
-        Handle<Map> map = receiver_types_->at(i);
-        ASSERT(!map.is_null() && *map != NULL);
-      }
+    int length = receiver_types_.length();
+    for (int i = 0; i < length; i++) {
+      Handle<Map> map = receiver_types_.at(i);
+      ASSERT(!map.is_null() && *map != NULL);
     }
   }
 #endif
@@ -805,9 +804,9 @@
   check_type_ = oracle->GetCallCheckType(this);
   if (is_monomorphic_) {
     Handle<Map> map;
-    if (receiver_types_ != NULL && receiver_types_->length() > 0) {
+    if (receiver_types_.length() > 0) {
       ASSERT(check_type_ == RECEIVER_MAP_CHECK);
-      map = receiver_types_->at(0);
+      map = receiver_types_.at(0);
     } else {
       ASSERT(check_type_ != RECEIVER_MAP_CHECK);
       holder_ = Handle<JSObject>(
diff --git a/src/ast.h b/src/ast.h
index b4705f6..74182d5 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -33,6 +33,7 @@
 #include "factory.h"
 #include "jsregexp.h"
 #include "runtime.h"
+#include "small-pointer-list.h"
 #include "token.h"
 #include "variables.h"
 
@@ -60,7 +61,7 @@
   V(ContinueStatement)                          \
   V(BreakStatement)                             \
   V(ReturnStatement)                            \
-  V(EnterWithContextStatement)                  \
+  V(WithStatement)                              \
   V(ExitContextStatement)                       \
   V(SwitchStatement)                            \
   V(DoWhileStatement)                           \
@@ -207,6 +208,36 @@
 };
 
 
+class SmallMapList {
+ public:
+  SmallMapList() {}
+  explicit SmallMapList(int capacity) : list_(capacity) {}
+
+  void Reserve(int capacity) { list_.Reserve(capacity); }
+  void Clear() { list_.Clear(); }
+
+  bool is_empty() const { return list_.is_empty(); }
+  int length() const { return list_.length(); }
+
+  void Add(Handle<Map> handle) {
+    list_.Add(handle.location());
+  }
+
+  Handle<Map> at(int i) const {
+    return Handle<Map>(list_.at(i));
+  }
+
+  Handle<Map> first() const { return at(0); }
+  Handle<Map> last() const { return at(length() - 1); }
+
+ private:
+  // The list stores pointers to Map*, that is Map**, so it's GC safe.
+  SmallPointerList<Map*> list_;
+
+  DISALLOW_COPY_AND_ASSIGN(SmallMapList);
+};
+
+
 class Expression: public AstNode {
  public:
   enum Context {
@@ -265,13 +296,15 @@
     UNREACHABLE();
     return false;
   }
-  virtual ZoneMapList* GetReceiverTypes() {
+  virtual SmallMapList* GetReceiverTypes() {
     UNREACHABLE();
     return NULL;
   }
-  virtual Handle<Map> GetMonomorphicReceiverType() {
-    UNREACHABLE();
-    return Handle<Map>();
+  Handle<Map> GetMonomorphicReceiverType() {
+    ASSERT(IsMonomorphic());
+    SmallMapList* types = GetReceiverTypes();
+    ASSERT(types != NULL && types->length() == 1);
+    return types->at(0);
   }
 
   unsigned id() const { return id_; }
@@ -359,9 +392,13 @@
   ZoneList<Statement*>* statements() { return &statements_; }
   bool is_initializer_block() const { return is_initializer_block_; }
 
+  Scope* block_scope() const { return block_scope_; }
+  void set_block_scope(Scope* block_scope) { block_scope_ = block_scope; }
+
  private:
   ZoneList<Statement*> statements_;
   bool is_initializer_block_;
+  Scope* block_scope_;
 };
 
 
@@ -371,9 +408,11 @@
       : proxy_(proxy),
         mode_(mode),
         fun_(fun) {
-    ASSERT(mode == Variable::VAR || mode == Variable::CONST);
+    ASSERT(mode == Variable::VAR ||
+           mode == Variable::CONST ||
+           mode == Variable::LET);
     // At the moment there are no "const functions"'s in JavaScript...
-    ASSERT(fun == NULL || mode == Variable::VAR);
+    ASSERT(fun == NULL || mode == Variable::VAR || mode == Variable::LET);
   }
 
   DECLARE_NODE_TYPE(Declaration)
@@ -627,19 +666,21 @@
 };
 
 
-class EnterWithContextStatement: public Statement {
+class WithStatement: public Statement {
  public:
-  explicit EnterWithContextStatement(Expression* expression)
-      : expression_(expression) { }
+  WithStatement(Expression* expression, Statement* statement)
+      : expression_(expression), statement_(statement) { }
 
-  DECLARE_NODE_TYPE(EnterWithContextStatement)
+  DECLARE_NODE_TYPE(WithStatement)
 
   Expression* expression() const { return expression_; }
+  Statement* statement() const { return statement_; }
 
   virtual bool IsInlineable() const;
 
  private:
   Expression* expression_;
+  Statement* statement_;
 };
 
 
@@ -1190,22 +1231,14 @@
 
 class Property: public Expression {
  public:
-  // Synthetic properties are property lookups introduced by the system,
-  // to objects that aren't visible to the user. Function calls to synthetic
-  // properties should use the global object as receiver, not the base object
-  // of the resolved Reference.
-  enum Type { NORMAL, SYNTHETIC };
   Property(Isolate* isolate,
            Expression* obj,
            Expression* key,
-           int pos,
-           Type type = NORMAL)
+           int pos)
       : Expression(isolate),
         obj_(obj),
         key_(key),
         pos_(pos),
-        type_(type),
-        receiver_types_(NULL),
         is_monomorphic_(false),
         is_array_length_(false),
         is_string_length_(false),
@@ -1220,7 +1253,6 @@
   Expression* obj() const { return obj_; }
   Expression* key() const { return key_; }
   virtual int position() const { return pos_; }
-  bool is_synthetic() const { return type_ == SYNTHETIC; }
 
   bool IsStringLength() const { return is_string_length_; }
   bool IsStringAccess() const { return is_string_access_; }
@@ -1229,25 +1261,20 @@
   // Type feedback information.
   void RecordTypeFeedback(TypeFeedbackOracle* oracle);
   virtual bool IsMonomorphic() { return is_monomorphic_; }
-  virtual ZoneMapList* GetReceiverTypes() { return receiver_types_; }
+  virtual SmallMapList* GetReceiverTypes() { return &receiver_types_; }
   virtual bool IsArrayLength() { return is_array_length_; }
-  virtual Handle<Map> GetMonomorphicReceiverType() {
-    return monomorphic_receiver_type_;
-  }
 
  private:
   Expression* obj_;
   Expression* key_;
   int pos_;
-  Type type_;
 
-  ZoneMapList* receiver_types_;
+  SmallMapList receiver_types_;
   bool is_monomorphic_ : 1;
   bool is_array_length_ : 1;
   bool is_string_length_ : 1;
   bool is_string_access_ : 1;
   bool is_function_prototype_ : 1;
-  Handle<Map> monomorphic_receiver_type_;
 };
 
 
@@ -1263,7 +1290,6 @@
         pos_(pos),
         is_monomorphic_(false),
         check_type_(RECEIVER_MAP_CHECK),
-        receiver_types_(NULL),
         return_id_(GetNextId(isolate)) {
   }
 
@@ -1277,7 +1303,7 @@
 
   void RecordTypeFeedback(TypeFeedbackOracle* oracle,
                           CallKind call_kind);
-  virtual ZoneMapList* GetReceiverTypes() { return receiver_types_; }
+  virtual SmallMapList* GetReceiverTypes() { return &receiver_types_; }
   virtual bool IsMonomorphic() { return is_monomorphic_; }
   CheckType check_type() const { return check_type_; }
   Handle<JSFunction> target() { return target_; }
@@ -1302,7 +1328,7 @@
 
   bool is_monomorphic_;
   CheckType check_type_;
-  ZoneMapList* receiver_types_;
+  SmallMapList receiver_types_;
   Handle<JSFunction> target_;
   Handle<JSObject> holder_;
   Handle<JSGlobalPropertyCell> cell_;
@@ -1477,8 +1503,7 @@
         expression_(expr),
         pos_(pos),
         assignment_id_(GetNextId(isolate)),
-        count_id_(GetNextId(isolate)),
-        receiver_types_(NULL) { }
+        count_id_(GetNextId(isolate)) {}
 
   DECLARE_NODE_TYPE(CountOperation)
 
@@ -1499,10 +1524,7 @@
 
   void RecordTypeFeedback(TypeFeedbackOracle* oracle);
   virtual bool IsMonomorphic() { return is_monomorphic_; }
-  virtual Handle<Map> GetMonomorphicReceiverType() {
-    return monomorphic_receiver_type_;
-  }
-  virtual ZoneMapList* GetReceiverTypes() { return receiver_types_; }
+  virtual SmallMapList* GetReceiverTypes() { return &receiver_types_; }
 
   // Bailout support.
   int AssignmentId() const { return assignment_id_; }
@@ -1516,8 +1538,7 @@
   int pos_;
   int assignment_id_;
   int count_id_;
-  Handle<Map> monomorphic_receiver_type_;
-  ZoneMapList* receiver_types_;
+  SmallMapList receiver_types_;
 };
 
 
@@ -1665,10 +1686,7 @@
   // Type feedback information.
   void RecordTypeFeedback(TypeFeedbackOracle* oracle);
   virtual bool IsMonomorphic() { return is_monomorphic_; }
-  virtual ZoneMapList* GetReceiverTypes() { return receiver_types_; }
-  virtual Handle<Map> GetMonomorphicReceiverType() {
-    return monomorphic_receiver_type_;
-  }
+  virtual SmallMapList* GetReceiverTypes() { return &receiver_types_; }
 
   // Bailout support.
   int CompoundLoadId() const { return compound_load_id_; }
@@ -1687,8 +1705,7 @@
   bool block_end_;
 
   bool is_monomorphic_;
-  ZoneMapList* receiver_types_;
-  Handle<Map> monomorphic_receiver_type_;
+  SmallMapList receiver_types_;
 };
 
 
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 5375cde..9f01664 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -199,6 +199,7 @@
   // New context initialization.  Used for creating a context from scratch.
   void InitializeGlobal(Handle<GlobalObject> inner_global,
                         Handle<JSFunction> empty_function);
+  void InitializeExperimentalGlobal();
   // Installs the contents of the native .js files on the global objects.
   // Used for creating a context from scratch.
   void InstallNativeFunctions();
@@ -1159,7 +1160,7 @@
 
 
   {
-    // Setup the call-as-function delegate.
+    // Set up the call-as-function delegate.
     Handle<Code> code =
         Handle<Code>(isolate->builtins()->builtin(
             Builtins::kHandleApiCallAsFunction));
@@ -1171,7 +1172,7 @@
   }
 
   {
-    // Setup the call-as-constructor delegate.
+    // Set up the call-as-constructor delegate.
     Handle<Code> code =
         Handle<Code>(isolate->builtins()->builtin(
             Builtins::kHandleApiCallAsConstructor));
@@ -1190,6 +1191,20 @@
 }
 
 
+void Genesis::InitializeExperimentalGlobal() {
+  Handle<JSObject> global = Handle<JSObject>(global_context()->global());
+
+  // TODO(mstarzinger): Move this into Genesis::InitializeGlobal once we no
+  // longer need to live behind a flag, so WeakMap gets added to the snapshot.
+  if (FLAG_harmony_weakmaps) {  // -- W e a k M a p
+    Handle<JSObject> prototype =
+        factory()->NewJSObject(isolate()->object_function(), TENURED);
+    InstallFunction(global, "WeakMap", JS_WEAK_MAP_TYPE, JSWeakMap::kSize,
+                    prototype, Builtins::kIllegal, true);
+  }
+}
+
+
 bool Genesis::CompileBuiltin(Isolate* isolate, int index) {
   Vector<const char> name = Natives::GetScriptName(index);
   Handle<String> source_code =
@@ -1680,6 +1695,11 @@
                "native proxy.js") == 0) {
       if (!CompileExperimentalBuiltin(isolate(), i)) return false;
     }
+    if (FLAG_harmony_weakmaps &&
+        strcmp(ExperimentalNatives::GetScriptName(i).start(),
+               "native weakmap.js") == 0) {
+      if (!CompileExperimentalBuiltin(isolate(), i)) return false;
+    }
   }
 
   InstallExperimentalNativeFunctions();
@@ -2169,7 +2189,8 @@
     isolate->counters()->contexts_created_from_scratch()->Increment();
   }
 
-  // Install experimental natives.
+  // Initialize experimental globals and install experimental natives.
+  InitializeExperimentalGlobal();
   if (!InstallExperimentalNatives()) return;
 
   result_ = global_context_;
diff --git a/src/checks.h b/src/checks.h
index a560b2f..2f359f6 100644
--- a/src/checks.h
+++ b/src/checks.h
@@ -251,9 +251,9 @@
 // actually causes each use to introduce a new defined type with a
 // name depending on the source line.
 template <int> class StaticAssertionHelper { };
-#define STATIC_CHECK(test)                                                  \
-  typedef                                                                   \
-    StaticAssertionHelper<sizeof(StaticAssertion<static_cast<bool>(test)>)> \
+#define STATIC_CHECK(test)                                                    \
+  typedef                                                                     \
+    StaticAssertionHelper<sizeof(StaticAssertion<static_cast<bool>((test))>)> \
     SEMI_STATIC_JOIN(__StaticAssertTypedef__, __LINE__)
 
 
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 1d1128f..5535d17 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -329,4 +329,84 @@
   stream->Add("CallFunctionStub_Args%d%s%s", argc_, in_loop_name, flags_name);
 }
 
+
+void ToBooleanStub::PrintName(StringStream* stream) {
+  stream->Add("ToBooleanStub_");
+  types_.Print(stream);
+}
+
+
+void ToBooleanStub::Types::Print(StringStream* stream) const {
+  if (IsEmpty()) stream->Add("None");
+  if (Contains(UNDEFINED)) stream->Add("Undefined");
+  if (Contains(BOOLEAN)) stream->Add("Bool");
+  if (Contains(NULL_TYPE)) stream->Add("Null");
+  if (Contains(SMI)) stream->Add("Smi");
+  if (Contains(SPEC_OBJECT)) stream->Add("SpecObject");
+  if (Contains(STRING)) stream->Add("String");
+  if (Contains(HEAP_NUMBER)) stream->Add("HeapNumber");
+}
+
+
+void ToBooleanStub::Types::TraceTransition(Types to) const {
+  if (!FLAG_trace_ic) return;
+  char buffer[100];
+  NoAllocationStringAllocator allocator(buffer,
+                                        static_cast<unsigned>(sizeof(buffer)));
+  StringStream stream(&allocator);
+  stream.Add("[ToBooleanIC (");
+  Print(&stream);
+  stream.Add("->");
+  to.Print(&stream);
+  stream.Add(")]\n");
+  stream.OutputToStdOut();
+}
+
+
+bool ToBooleanStub::Types::Record(Handle<Object> object) {
+  if (object->IsUndefined()) {
+    Add(UNDEFINED);
+    return false;
+  } else if (object->IsBoolean()) {
+    Add(BOOLEAN);
+    return object->IsTrue();
+  } else if (object->IsNull()) {
+    Add(NULL_TYPE);
+    return false;
+  } else if (object->IsSmi()) {
+    Add(SMI);
+    return Smi::cast(*object)->value() != 0;
+  } else if (object->IsSpecObject()) {
+    Add(SPEC_OBJECT);
+    return !object->IsUndetectableObject();
+  } else if (object->IsString()) {
+    Add(STRING);
+    return !object->IsUndetectableObject() &&
+        String::cast(*object)->length() != 0;
+  } else if (object->IsHeapNumber()) {
+    ASSERT(!object->IsUndetectableObject());
+    Add(HEAP_NUMBER);
+    double value = HeapNumber::cast(*object)->value();
+    return value != 0 && !isnan(value);
+  } else {
+    // We should never see an internal object at runtime here!
+    UNREACHABLE();
+    return true;
+  }
+}
+
+
+bool ToBooleanStub::Types::NeedsMap() const {
+  return Contains(ToBooleanStub::SPEC_OBJECT)
+      || Contains(ToBooleanStub::STRING)
+      || Contains(ToBooleanStub::HEAP_NUMBER);
+}
+
+
+bool ToBooleanStub::Types::CanBeUndetectable() const {
+  return Contains(ToBooleanStub::SPEC_OBJECT)
+      || Contains(ToBooleanStub::STRING);
+}
+
+
 } }  // namespace v8::internal
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 17c245c..89e99a8 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -900,14 +900,66 @@
 
 class ToBooleanStub: public CodeStub {
  public:
-  explicit ToBooleanStub(Register tos) : tos_(tos) { }
+  enum Type {
+    UNDEFINED,
+    BOOLEAN,
+    NULL_TYPE,
+    SMI,
+    SPEC_OBJECT,
+    STRING,
+    HEAP_NUMBER,
+    NUMBER_OF_TYPES
+  };
+
+  // At most 8 different types can be distinguished, because the Code object
+  // only has room for a single byte to hold a set of these types. :-P
+  STATIC_ASSERT(NUMBER_OF_TYPES <= 8);
+
+  class Types {
+   public:
+    Types() {}
+    explicit Types(byte bits) : set_(bits) {}
+
+    bool IsEmpty() const { return set_.IsEmpty(); }
+    bool Contains(Type type) const { return set_.Contains(type); }
+    void Add(Type type) { set_.Add(type); }
+    byte ToByte() const { return set_.ToIntegral(); }
+    void Print(StringStream* stream) const;
+    void TraceTransition(Types to) const;
+    bool Record(Handle<Object> object);
+    bool NeedsMap() const;
+    bool CanBeUndetectable() const;
+
+   private:
+    EnumSet<Type, byte> set_;
+  };
+
+  static Types no_types() { return Types(); }
+  static Types all_types() { return Types((1 << NUMBER_OF_TYPES) - 1); }
+
+  explicit ToBooleanStub(Register tos, Types types = Types())
+      : tos_(tos), types_(types) { }
 
   void Generate(MacroAssembler* masm);
+  virtual int GetCodeKind() { return Code::TO_BOOLEAN_IC; }
+  virtual void PrintName(StringStream* stream);
 
  private:
-  Register tos_;
   Major MajorKey() { return ToBoolean; }
-  int MinorKey() { return tos_.code(); }
+  int MinorKey() { return (tos_.code() << NUMBER_OF_TYPES) | types_.ToByte(); }
+
+  virtual void FinishCode(Code* code) {
+    code->set_to_boolean_state(types_.ToByte());
+  }
+
+  void CheckOddball(MacroAssembler* masm,
+                    Type type,
+                    Heap::RootListIndex value,
+                    bool result);
+  void GenerateTypeTransition(MacroAssembler* masm);
+
+  Register tos_;
+  Types types_;
 };
 
 } }  // namespace v8::internal
diff --git a/src/codegen.cc b/src/codegen.cc
index fb723a3..cdc9ba1 100644
--- a/src/codegen.cc
+++ b/src/codegen.cc
@@ -169,7 +169,6 @@
 #endif  // ENABLE_DISASSEMBLER
 }
 
-static Vector<const char> kRegexp = CStrVector("regexp");
 
 bool CodeGenerator::ShouldGenerateLog(Expression* type) {
   ASSERT(type != NULL);
@@ -179,7 +178,7 @@
   }
   Handle<String> name = Handle<String>::cast(type->AsLiteral()->handle());
   if (FLAG_log_regexp) {
-    if (name->IsEqualTo(kRegexp))
+    if (name->IsEqualTo(CStrVector("regexp")))
       return true;
   }
   return false;
diff --git a/src/compiler.cc b/src/compiler.cc
old mode 100755
new mode 100644
index abff8b6..b33c374
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -478,15 +478,21 @@
     // that would be compiled lazily anyway, so we skip the preparse step
     // in that case too.
     ScriptDataImpl* pre_data = input_pre_data;
+    bool harmony_block_scoping = natives != NATIVES_CODE &&
+                                 FLAG_harmony_block_scoping;
     if (pre_data == NULL
         && source_length >= FLAG_min_preparse_length) {
       if (source->IsExternalTwoByteString()) {
         ExternalTwoByteStringUC16CharacterStream stream(
             Handle<ExternalTwoByteString>::cast(source), 0, source->length());
-        pre_data = ParserApi::PartialPreParse(&stream, extension);
+        pre_data = ParserApi::PartialPreParse(&stream,
+                                              extension,
+                                              harmony_block_scoping);
       } else {
         GenericStringUC16CharacterStream stream(source, 0, source->length());
-        pre_data = ParserApi::PartialPreParse(&stream, extension);
+        pre_data = ParserApi::PartialPreParse(&stream,
+                                              extension,
+                                              harmony_block_scoping);
       }
     }
 
diff --git a/src/contexts.cc b/src/contexts.cc
index d066d34..4f93abd 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -87,13 +87,15 @@
 Handle<Object> Context::Lookup(Handle<String> name,
                                ContextLookupFlags flags,
                                int* index_,
-                               PropertyAttributes* attributes) {
+                               PropertyAttributes* attributes,
+                               BindingFlags* binding_flags) {
   Isolate* isolate = GetIsolate();
   Handle<Context> context(this, isolate);
 
   bool follow_context_chain = (flags & FOLLOW_CONTEXT_CHAIN) != 0;
   *index_ = -1;
   *attributes = ABSENT;
+  *binding_flags = MISSING_BINDING;
 
   if (FLAG_trace_contexts) {
     PrintF("Context::Lookup(");
@@ -109,7 +111,7 @@
     }
 
     // Check extension/with/global object.
-    if (context->has_extension()) {
+    if (!context->IsBlockContext() && context->has_extension()) {
       if (context->IsCatchContext()) {
         // Catch contexts have the variable name in the extension slot.
         if (name->Equals(String::cast(context->extension()))) {
@@ -118,9 +120,13 @@
           }
           *index_ = Context::THROWN_OBJECT_INDEX;
           *attributes = NONE;
+          *binding_flags = MUTABLE_IS_INITIALIZED;
           return context;
         }
       } else {
+        ASSERT(context->IsGlobalContext() ||
+               context->IsFunctionContext() ||
+               context->IsWithContext());
         // Global, function, and with contexts may have an object in the
         // extension slot.
         Handle<JSObject> extension(JSObject::cast(context->extension()),
@@ -145,11 +151,20 @@
       }
     }
 
-    // Only functions can have locals, parameters, and a function name.
-    if (context->IsFunctionContext()) {
+    // Check serialized scope information of functions and blocks. Only
+    // functions can have parameters, and a function name.
+    if (context->IsFunctionContext() || context->IsBlockContext()) {
       // We may have context-local slots.  Check locals in the context.
-      Handle<SerializedScopeInfo> scope_info(
-          context->closure()->shared()->scope_info(), isolate);
+      Handle<SerializedScopeInfo> scope_info;
+      if (context->IsFunctionContext()) {
+        scope_info = Handle<SerializedScopeInfo>(
+            context->closure()->shared()->scope_info(), isolate);
+      } else {
+        ASSERT(context->IsBlockContext());
+        scope_info = Handle<SerializedScopeInfo>(
+            SerializedScopeInfo::cast(context->extension()), isolate);
+      }
+
       Variable::Mode mode;
       int index = scope_info->ContextSlotIndex(*name, &mode);
       ASSERT(index < 0 || index >= MIN_CONTEXT_SLOTS);
@@ -169,9 +184,15 @@
           case Variable::INTERNAL:  // Fall through.
           case Variable::VAR:
             *attributes = NONE;
+            *binding_flags = MUTABLE_IS_INITIALIZED;
+            break;
+          case Variable::LET:
+            *attributes = NONE;
+            *binding_flags = MUTABLE_CHECK_INITIALIZED;
             break;
           case Variable::CONST:
             *attributes = READ_ONLY;
+            *binding_flags = IMMUTABLE_CHECK_INITIALIZED;
             break;
           case Variable::DYNAMIC:
           case Variable::DYNAMIC_GLOBAL:
@@ -194,6 +215,7 @@
           }
           *index_ = index;
           *attributes = READ_ONLY;
+          *binding_flags = IMMUTABLE_IS_INITIALIZED;
           return context;
         }
       }
diff --git a/src/contexts.h b/src/contexts.h
index 53b40f1..505f86c 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -44,6 +44,30 @@
 };
 
 
+// ES5 10.2 defines lexical environments with mutable and immutable bindings.
+// Immutable bindings have two states, initialized and uninitialized, and
+// their state is changed by the InitializeImmutableBinding method.
+//
+// The harmony proposal for block scoped bindings also introduces the
+// uninitialized state for mutable bindings. A 'let' declared variable
+// is a mutable binding that is created uninitalized upon activation of its
+// lexical environment and it is initialized when evaluating its declaration
+// statement. Var declared variables are mutable bindings that are
+// immediately initialized upon creation. The BindingFlags enum represents
+// information if a binding has definitely been initialized. 'const' declared
+// variables are created as uninitialized immutable bindings.
+
+// In harmony mode accessing an uninitialized binding produces a reference
+// error.
+enum BindingFlags {
+  MUTABLE_IS_INITIALIZED,
+  MUTABLE_CHECK_INITIALIZED,
+  IMMUTABLE_IS_INITIALIZED,
+  IMMUTABLE_CHECK_INITIALIZED,
+  MISSING_BINDING
+};
+
+
 // Heap-allocated activation contexts.
 //
 // Contexts are implemented as FixedArray objects; the Context
@@ -295,6 +319,10 @@
     Map* map = this->map();
     return map == map->GetHeap()->with_context_map();
   }
+  bool IsBlockContext() {
+    Map* map = this->map();
+    return map == map->GetHeap()->block_context_map();
+  }
 
   // Tells whether the global context is marked with out of memory.
   inline bool has_out_of_memory();
@@ -347,8 +375,11 @@
   // 4) index_ < 0 && result.is_null():
   //    there was no context found with the corresponding property.
   //    attributes == ABSENT.
-  Handle<Object> Lookup(Handle<String> name, ContextLookupFlags flags,
-                        int* index_, PropertyAttributes* attributes);
+  Handle<Object> Lookup(Handle<String> name,
+                        ContextLookupFlags flags,
+                        int* index_,
+                        PropertyAttributes* attributes,
+                        BindingFlags* binding_flags);
 
   // Determine if a local variable with the given name exists in a
   // context.  Do not consider context extension objects.  This is
diff --git a/src/cpu-profiler.cc b/src/cpu-profiler.cc
index bb480fc..8b3333e 100644
--- a/src/cpu-profiler.cc
+++ b/src/cpu-profiler.cc
@@ -562,12 +562,12 @@
     sampler->Stop();
     need_to_stop_sampler_ = false;
   }
+  NoBarrier_Store(&is_profiling_, false);
   processor_->Stop();
   processor_->Join();
   delete processor_;
   delete generator_;
   processor_ = NULL;
-  NoBarrier_Store(&is_profiling_, false);
   generator_ = NULL;
   logger->logging_nesting_ = saved_logging_nesting_;
 }
diff --git a/src/d8.cc b/src/d8.cc
index 5fd9d27..4d7e988 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -26,8 +26,8 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 
-#ifdef V8_SHARED
-#define USING_V8_SHARED
+#ifdef USING_V8_SHARED  // Defined when linking against shared lib on Windows.
+#define V8_SHARED
 #endif
 
 #ifdef COMPRESS_STARTUP_DATA_BZ2
@@ -37,15 +37,16 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
 #include <assert.h>
 #include "../include/v8-testing.h"
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 #include "d8.h"
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 #include "api.h"
 #include "checks.h"
 #include "d8-debug.h"
@@ -53,20 +54,20 @@
 #include "natives.h"
 #include "platform.h"
 #include "v8.h"
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 #if !defined(_WIN32) && !defined(_WIN64)
 #include <unistd.h>  // NOLINT
 #endif
 
-#ifdef USING_V8_SHARED
+#ifndef ASSERT
 #define ASSERT(condition) assert(condition)
-#endif  // USING_V8_SHARED
+#endif
 
 namespace v8 {
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 LineEditor *LineEditor::first_ = NULL;
 const char* Shell::kHistoryFileName = ".d8_history";
 
@@ -116,20 +117,20 @@
 CounterCollection* Shell::counters_ = &local_counters_;
 i::Mutex* Shell::context_mutex_(i::OS::CreateMutex());
 Persistent<Context> Shell::utility_context_;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 Persistent<Context> Shell::evaluation_context_;
 ShellOptions Shell::options;
 const char* Shell::kPrompt = "d8> ";
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 bool CounterMap::Match(void* key1, void* key2) {
   const char* name1 = reinterpret_cast<const char*>(key1);
   const char* name2 = reinterpret_cast<const char*>(key2);
   return strcmp(name1, name2) == 0;
 }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 // Converts a V8 value to a C string.
@@ -143,11 +144,11 @@
                           Handle<Value> name,
                           bool print_result,
                           bool report_exceptions) {
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   bool FLAG_debugger = i::FLAG_debugger;
 #else
   bool FLAG_debugger = false;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   HandleScope handle_scope;
   TryCatch try_catch;
   options.script_executed = true;
@@ -199,7 +200,7 @@
       printf(" ");
     }
     v8::String::Utf8Value str(args[i]);
-    int n = fwrite(*str, sizeof(**str), str.length(), stdout);
+    int n = static_cast<int>(fwrite(*str, sizeof(**str), str.length(), stdout));
     if (n != str.length()) {
       printf("Error in fwrite\n");
       exit(1);
@@ -226,17 +227,24 @@
   static const int kBufferSize = 256;
   char buffer[kBufferSize];
   Handle<String> accumulator = String::New("");
-  bool linebreak;
   int length;
-  do {  // Repeat if the line ends with an escape '\'.
-    // fgets got an error. Just give up.
+  while (true) {
+    // Continue reading if the line ends with an escape '\\' or the line has
+    // not been fully read into the buffer yet (does not end with '\n').
+    // If fgets gets an error, just give up.
     if (fgets(buffer, kBufferSize, stdin) == NULL) return Null();
-    length = strlen(buffer);
-    linebreak = (length > 1 && buffer[length-2] == '\\');
-    if (linebreak) buffer[length-2] = '\n';
-    accumulator = String::Concat(accumulator, String::New(buffer, length-1));
-  } while (linebreak);
-  return accumulator;
+    length = static_cast<int>(strlen(buffer));
+    if (length == 0) {
+      return accumulator;
+    } else if (buffer[length-1] != '\n') {
+      accumulator = String::Concat(accumulator, String::New(buffer, length));
+    } else if (length > 1 && buffer[length-2] == '\\') {
+      buffer[length-2] = '\n';
+      accumulator = String::Concat(accumulator, String::New(buffer, length-1));
+    } else {
+      return String::Concat(accumulator, String::New(buffer, length-1));
+    }
+  }
 }
 
 
@@ -269,9 +277,9 @@
         String::New("Array constructor needs one parameter."));
   }
   static const int kMaxLength = 0x3fffffff;
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   ASSERT(kMaxLength == i::ExternalArray::kMaxLength);
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   size_t length = 0;
   if (args[0]->IsUint32()) {
     length = args[0]->Uint32Value();
@@ -299,9 +307,12 @@
   Persistent<Object> persistent_array = Persistent<Object>::New(array);
   persistent_array.MakeWeak(data, ExternalArrayWeakCallback);
   persistent_array.MarkIndependent();
-  array->SetIndexedPropertiesToExternalArrayData(data, type, length);
-  array->Set(String::New("length"), Int32::New(length), ReadOnly);
-  array->Set(String::New("BYTES_PER_ELEMENT"), Int32::New(element_size));
+  array->SetIndexedPropertiesToExternalArrayData(data, type,
+                                                 static_cast<int>(length));
+  array->Set(String::New("length"),
+             Int32::New(static_cast<int32_t>(length)), ReadOnly);
+  array->Set(String::New("BYTES_PER_ELEMENT"),
+             Int32::New(static_cast<int32_t>(element_size)));
   return array;
 }
 
@@ -368,9 +379,9 @@
 
 Handle<Value> Shell::Quit(const Arguments& args) {
   int exit_code = args[0]->Int32Value();
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   OnExit();
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   exit(exit_code);
   return Undefined();
 }
@@ -419,7 +430,7 @@
 }
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 Handle<Array> Shell::GetCompletions(Handle<String> text, Handle<String> full) {
   HandleScope handle_scope;
   Context::Scope context_scope(utility_context_);
@@ -454,10 +465,10 @@
   return val;
 }
 #endif  // ENABLE_DEBUGGER_SUPPORT
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 int32_t* Counter::Bind(const char* name, bool is_histogram) {
   int i;
   for (i = 0; i < kMaxNameSize - 1 && name[i]; i++)
@@ -605,7 +616,7 @@
   }
 #endif  // ENABLE_DEBUGGER_SUPPORT
 }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 #ifdef COMPRESS_STARTUP_DATA_BZ2
@@ -667,16 +678,16 @@
                        FunctionTemplate::New(PixelArray));
 
 #ifdef LIVE_OBJECT_LIST
-  global_template->Set(String::New("lol_is_enabled"), Boolean::New(true));
+  global_template->Set(String::New("lol_is_enabled"), True());
 #else
-  global_template->Set(String::New("lol_is_enabled"), Boolean::New(false));
+  global_template->Set(String::New("lol_is_enabled"), False());
 #endif
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   Handle<ObjectTemplate> os_templ = ObjectTemplate::New();
   AddOSMethods(os_templ);
   global_template->Set(String::New("os"), os_templ);
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
   return global_template;
 }
@@ -692,7 +703,7 @@
   }
 #endif
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   Shell::counter_map_ = new CounterMap();
   // Set up counters
   if (i::StrLength(i::FLAG_map_counters) != 0)
@@ -702,10 +713,10 @@
     V8::SetCreateHistogramFunction(CreateHistogram);
     V8::SetAddHistogramSampleFunction(AddHistogramSample);
   }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   if (options.test_shell) return;
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   Locker lock;
   HandleScope scope;
   Handle<ObjectTemplate> global_template = CreateGlobalTemplate();
@@ -717,21 +728,22 @@
     v8::Debug::EnableAgent("d8 shell", i::FLAG_debugger_port, true);
   }
 #endif  // ENABLE_DEBUGGER_SUPPORT
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 }
 
 
 Persistent<Context> Shell::CreateEvaluationContext() {
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   // This needs to be a critical section since this is not thread-safe
   i::ScopedLock lock(context_mutex_);
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   // Initialize the global objects
   Handle<ObjectTemplate> global_template = CreateGlobalTemplate();
   Persistent<Context> context = Context::New(NULL, global_template);
+  ASSERT(!context.IsEmpty());
   Context::Scope scope(context);
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   i::JSArguments js_args = i::FLAG_js_arguments;
   i::Handle<i::FixedArray> arguments_array =
       FACTORY->NewFixedArray(js_args.argc());
@@ -744,12 +756,12 @@
       FACTORY->NewJSArrayWithElements(arguments_array);
   context->Global()->Set(String::New("arguments"),
                          Utils::ToLocal(arguments_jsarray));
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   return context;
 }
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 void Shell::OnExit() {
   if (i::FLAG_dump_counters) {
     printf("+----------------------------------------+-------------+\n");
@@ -769,18 +781,34 @@
   if (counters_file_ != NULL)
     delete counters_file_;
 }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
+
+
+static FILE* FOpen(const char* path, const char* mode) {
+#if (defined(_WIN32) || defined(_WIN64))
+  FILE* result;
+  if (fopen_s(&result, path, mode) == 0) {
+    return result;
+  } else {
+    return NULL;
+  }
+#else
+  FILE* file = fopen(path, mode);
+  if (file == NULL) return NULL;
+  struct stat file_stat;
+  if (fstat(fileno(file), &file_stat) != 0) return NULL;
+  bool is_regular_file = ((file_stat.st_mode & S_IFREG) != 0);
+  if (is_regular_file) return file;
+  fclose(file);
+  return NULL;
+#endif
+}
 
 
 static char* ReadChars(const char* name, int* size_out) {
   // Release the V8 lock while reading files.
   v8::Unlocker unlocker(Isolate::GetCurrent());
-#ifndef USING_V8_SHARED
-  FILE* file = i::OS::FOpen(name, "rb");
-#else
-  // TODO(yangguo@chromium.org): reading from a directory hangs!
-  FILE* file = fopen(name, "rb");
-#endif  // USING_V8_SHARED
+  FILE* file = FOpen(name, "rb");
   if (file == NULL) return NULL;
 
   fseek(file, 0, SEEK_END);
@@ -790,7 +818,7 @@
   char* chars = new char[size + 1];
   chars[size] = '\0';
   for (int i = 0; i < size;) {
-    int read = fread(&chars[i], 1, size - i, file);
+    int read = static_cast<int>(fread(&chars[i], 1, size - i, file));
     i += read;
   }
   fclose(file);
@@ -799,7 +827,7 @@
 }
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 static char* ReadToken(char* data, char token) {
   char* next = i::OS::StrChr(data, token);
   if (next != NULL) {
@@ -819,7 +847,7 @@
 static char* ReadWord(char* data) {
   return ReadToken(data, ' ');
 }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 // Reads a file into a v8 string.
@@ -838,7 +866,7 @@
   Context::Scope context_scope(evaluation_context_);
   HandleScope handle_scope;
   Handle<String> name = String::New("(d8)");
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   LineEditor* editor = LineEditor::Get();
   printf("V8 version %s [console: %s]\n", V8::GetVersion(), editor->name());
   if (i::FLAG_debugger) {
@@ -861,12 +889,12 @@
     if (fgets(buffer, kBufferSize, stdin) == NULL) break;
     ExecuteString(String::New(buffer), name, true, true);
   }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   printf("\n");
 }
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 class ShellThread : public i::Thread {
  public:
   ShellThread(int no, i::Vector<const char> files)
@@ -919,7 +947,7 @@
     ptr = next_line;
   }
 }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 void SourceGroup::ExitShell(int exit_code) {
@@ -966,32 +994,16 @@
 
 
 Handle<String> SourceGroup::ReadFile(const char* name) {
-#ifndef USING_V8_SHARED
-  FILE* file = i::OS::FOpen(name, "rb");
-#else
-  // TODO(yangguo@chromium.org): reading from a directory hangs!
-  FILE* file = fopen(name, "rb");
-#endif  // USING_V8_SHARED
-  if (file == NULL) return Handle<String>();
-
-  fseek(file, 0, SEEK_END);
-  int size = ftell(file);
-  rewind(file);
-
-  char* chars = new char[size + 1];
-  chars[size] = '\0';
-  for (int i = 0; i < size;) {
-    int read = fread(&chars[i], 1, size - i, file);
-    i += read;
-  }
-  fclose(file);
+  int size;
+  const char* chars = ReadChars(name, &size);
+  if (chars == NULL) return Handle<String>();
   Handle<String> result = String::New(chars, size);
   delete[] chars;
   return result;
 }
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 i::Thread::Options SourceGroup::GetThreadOptions() {
   i::Thread::Options options;
   options.name = "IsolateThread";
@@ -1043,7 +1055,7 @@
     done_semaphore_->Wait();
   }
 }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 bool Shell::SetOptions(int argc, char* argv[]) {
@@ -1065,23 +1077,23 @@
       options.test_shell = true;
       argv[i] = NULL;
     } else if (strcmp(argv[i], "--preemption") == 0) {
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
       printf("D8 with shared library does not support multi-threading\n");
       return false;
 #else
       options.use_preemption = true;
       argv[i] = NULL;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
     } else if (strcmp(argv[i], "--no-preemption") == 0) {
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
       printf("D8 with shared library does not support multi-threading\n");
       return false;
 #else
       options.use_preemption = false;
       argv[i] = NULL;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
     } else if (strcmp(argv[i], "--preemption-interval") == 0) {
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
       printf("D8 with shared library does not support multi-threading\n");
       return false;
 #else
@@ -1100,19 +1112,19 @@
         printf("Missing value for --preemption-interval\n");
         return false;
       }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
     } else if (strcmp(argv[i], "-f") == 0) {
       // Ignore any -f flags for compatibility with other stand-alone
       // JavaScript engines.
       continue;
     } else if (strcmp(argv[i], "--isolate") == 0) {
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
       printf("D8 with shared library does not support multi-threading\n");
       return false;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
       options.num_isolates++;
     }
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
     else if (strcmp(argv[i], "--dump-counters") == 0) {
       printf("D8 with shared library does not include counters\n");
       return false;
@@ -1123,10 +1135,10 @@
       printf("Javascript debugger not included\n");
       return false;
     }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   }
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   // Run parallel threads if we are not using --isolate
   for (int i = 1; i < argc; i++) {
     if (argv[i] == NULL) continue;
@@ -1147,9 +1159,10 @@
       }
       argv[i] = NULL;
       options.parallel_files->Add(i::Vector<const char>(files, size));
+      delete[] files;
     }
   }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
   v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
 
@@ -1174,7 +1187,7 @@
 
 
 int Shell::RunMain(int argc, char* argv[]) {
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   i::List<i::Thread*> threads(1);
   if (options.parallel_files != NULL)
     for (int i = 0; i < options.parallel_files->length(); i++) {
@@ -1187,7 +1200,7 @@
   for (int i = 1; i < options.num_isolates; ++i) {
     options.isolate_sources[i].StartExecuteInThread();
   }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   {  // NOLINT
     Locker lock;
     HandleScope scope;
@@ -1211,17 +1224,17 @@
       context.Dispose();
     }
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
     // Start preemption if threads have been created and preemption is enabled.
     if (options.parallel_files != NULL
         && threads.length() > 0
         && options.use_preemption) {
       Locker::StartPreemption(options.preemption_interval);
     }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   }
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   for (int i = 1; i < options.num_isolates; ++i) {
     options.isolate_sources[i].WaitForThread();
   }
@@ -1232,9 +1245,7 @@
       thread->Join();
       delete thread;
     }
-
-  OnExit();
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   return 0;
 }
 
@@ -1262,14 +1273,14 @@
   }
 
 
-#if !defined(USING_V8_SHARED) && defined(ENABLE_DEBUGGER_SUPPORT)
+#if !defined(V8_SHARED) && defined(ENABLE_DEBUGGER_SUPPORT)
   // Run remote debugger if requested, but never on --test
   if (i::FLAG_remote_debugger && !options.test_shell) {
     InstallUtilityScript();
     RunRemoteDebugger(i::FLAG_debugger_port);
     return 0;
   }
-#endif  // !USING_V8_SHARED && ENABLE_DEBUGGER_SUPPORT
+#endif  // !V8_SHARED && ENABLE_DEBUGGER_SUPPORT
 
   // Run interactive shell if explicitly requested or if no script has been
   // executed, but never on --test
@@ -1277,16 +1288,20 @@
   if (( options.interactive_shell
       || !options.script_executed )
       && !options.test_shell ) {
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
     if (!i::FLAG_debugger) {
       InstallUtilityScript();
     }
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
     RunShell();
   }
 
   V8::Dispose();
 
+#ifndef V8_SHARED
+  OnExit();
+#endif  // V8_SHARED
+
   return result;
 }
 
diff --git a/src/d8.gyp b/src/d8.gyp
index 48442b1..70186cf 100644
--- a/src/d8.gyp
+++ b/src/d8.gyp
@@ -1,4 +1,4 @@
-# Copyright 2011 the V8 project authors. All rights reserved.
+# Copyright 2010 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
@@ -26,6 +26,7 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 {
+  'includes': ['../build/common.gypi'],
   'variables': {
     'console%': '',
   },
@@ -36,6 +37,7 @@
       'dependencies': [
         '../tools/gyp/v8.gyp:v8',
       ],
+      # Generated source files need this explicitly:
       'include_dirs+': [
         '../src',
       ],
@@ -47,9 +49,17 @@
       ],
       'conditions': [
         [ 'component!="shared_library"', {
-          'dependencies': [ 'd8_js2c#host', ], 
           'sources': [ 'd8-debug.cc', '<(SHARED_INTERMEDIATE_DIR)/d8-js.cc', ],
           'conditions': [
+            [ 'want_separate_host_toolset==1', {
+              'dependencies': [
+                'd8_js2c#host',
+              ],
+            }, {
+              'dependencies': [
+                'd8_js2c',
+              ],
+            }],
             [ 'console=="readline"', {
               'libraries': [ '-lreadline', ],
               'sources': [ 'd8-readline.cc' ],
@@ -68,13 +78,19 @@
     {
       'target_name': 'd8_js2c',
       'type': 'none',
-      'toolsets': ['host'],
       'variables': {
         'js_files': [
           'd8.js',
           'macros.py',
         ],
       },
+      'conditions': [
+        [ 'want_separate_host_toolset==1', {
+          'toolsets': ['host'],
+        }, {
+          'toolsets': ['target'],
+        }]
+      ],
       'actions': [
         {
           'action_name': 'd8_js2c',
diff --git a/src/d8.h b/src/d8.h
index 840ca1e..28321f5 100644
--- a/src/d8.h
+++ b/src/d8.h
@@ -29,22 +29,18 @@
 #define V8_D8_H_
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 #include "v8.h"
 #include "allocation.h"
 #include "hashmap.h"
 #else
 #include "../include/v8.h"
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 namespace v8 {
 
-#ifndef USING_V8_SHARED
-namespace i = v8::internal;
-#endif  // USING_V8_SHARED
 
-
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 // A single counter in a counter collection.
 class Counter {
  public:
@@ -117,17 +113,17 @@
   static bool Match(void* key1, void* key2);
   i::HashMap hash_map_;
 };
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 class SourceGroup {
  public:
   SourceGroup() :
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
       next_semaphore_(v8::internal::OS::CreateSemaphore(0)),
       done_semaphore_(v8::internal::OS::CreateSemaphore(0)),
       thread_(NULL),
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
       argv_(NULL),
       begin_offset_(0),
       end_offset_(0) { }
@@ -141,7 +137,7 @@
 
   void Execute();
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   void StartExecuteInThread();
   void WaitForThread();
 
@@ -165,7 +161,7 @@
   i::Semaphore* next_semaphore_;
   i::Semaphore* done_semaphore_;
   i::Thread* thread_;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
   void ExitShell(int exit_code);
   Handle<String> ReadFile(const char* name);
@@ -179,11 +175,11 @@
 class ShellOptions {
  public:
   ShellOptions() :
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
      use_preemption(true),
      preemption_interval(10),
      parallel_files(NULL),
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
      script_executed(false),
      last_run(true),
      stress_opt(false),
@@ -193,11 +189,11 @@
      num_isolates(1),
      isolate_sources(NULL) { }
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   bool use_preemption;
   int preemption_interval;
   i::List< i::Vector<const char> >* parallel_files;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   bool script_executed;
   bool last_run;
   bool stress_opt;
@@ -208,11 +204,11 @@
   SourceGroup* isolate_sources;
 };
 
-#ifdef USING_V8_SHARED
+#ifdef V8_SHARED
 class Shell {
 #else
 class Shell : public i::AllStatic {
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
  public:
   static bool ExecuteString(Handle<String> source,
                             Handle<Value> name,
@@ -225,7 +221,7 @@
   static int RunMain(int argc, char* argv[]);
   static int Main(int argc, char* argv[]);
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   static Handle<Array> GetCompletions(Handle<String> text,
                                       Handle<String> full);
   static void OnExit();
@@ -236,7 +232,7 @@
                                size_t buckets);
   static void AddHistogramSample(void* histogram, int sample);
   static void MapCounters(const char* name);
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
   static Handle<Object> DebugMessageDetails(Handle<String> message);
@@ -300,15 +296,15 @@
   static Handle<Value> RemoveDirectory(const Arguments& args);
 
   static void AddOSMethods(Handle<ObjectTemplate> os_template);
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   static const char* kHistoryFileName;
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   static const char* kPrompt;
   static ShellOptions options;
 
  private:
   static Persistent<Context> evaluation_context_;
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
   static Persistent<Context> utility_context_;
   static CounterMap* counter_map_;
   // We statically allocate a set of local counters to be used if we
@@ -320,7 +316,7 @@
 
   static Counter* GetCounter(const char* name, bool is_histogram);
   static void InstallUtilityScript();
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
   static void Initialize();
   static void RunShell();
   static bool SetOptions(int argc, char* argv[]);
@@ -332,7 +328,7 @@
 };
 
 
-#ifndef USING_V8_SHARED
+#ifndef V8_SHARED
 class LineEditor {
  public:
   enum Type { DUMB = 0, READLINE = 1 };
@@ -352,7 +348,7 @@
   LineEditor* next_;
   static LineEditor* first_;
 };
-#endif  // USING_V8_SHARED
+#endif  // V8_SHARED
 
 
 }  // namespace v8
diff --git a/src/d8.js b/src/d8.js
index 033455e..a2b9585 100644
--- a/src/d8.js
+++ b/src/d8.js
@@ -103,7 +103,8 @@
                     Local: 1,
                     With: 2,
                     Closure: 3,
-                    Catch: 4 };
+                    Catch: 4,
+                    Block: 5 };
 
 
 // Current debug state.
@@ -391,14 +392,14 @@
           this.frameCommandToJSONRequest_('' +
                                           (Debug.State.currentFrame + 1));
       break;
-      
+
     case 'down':
     case 'do':
       this.request_ =
           this.frameCommandToJSONRequest_('' +
                                           (Debug.State.currentFrame - 1));
       break;
-      
+
     case 'set':
     case 'print':
     case 'p':
@@ -1071,7 +1072,7 @@
         arg2 = 'uncaught';
       }
       excType = arg2;
-      
+
     // Check for:
     //   en[able] [all|unc[aught]] exc[eptions]
     //   dis[able] [all|unc[aught]] exc[eptions]
@@ -1130,7 +1131,7 @@
         request.arguments.ignoreCount = parseInt(otherArgs);
         break;
       default:
-        throw new Error('Invalid arguments.');  
+        throw new Error('Invalid arguments.');
     }
   } else {
     throw new Error('Invalid arguments.');
@@ -1251,7 +1252,7 @@
       start_index = parseInt(args[i]);
       // The user input start index starts at 1:
       if (start_index <= 0) {
-        throw new Error('Invalid index ' + args[i] + '.');                
+        throw new Error('Invalid index ' + args[i] + '.');
       }
       start_index -= 1;
       is_verbose = true;
@@ -2020,7 +2021,7 @@
         } else if (body.breakOnUncaughtExceptions) {
           result += '* breaking on UNCAUGHT exceptions is enabled\n';
         } else {
-          result += '* all exception breakpoints are disabled\n';            
+          result += '* all exception breakpoints are disabled\n';
         }
         details.text = result;
         break;
diff --git a/src/debug-debugger.js b/src/debug-debugger.js
index 36b624e..d254ee5 100644
--- a/src/debug-debugger.js
+++ b/src/debug-debugger.js
@@ -404,7 +404,7 @@
       return this.script_name_ == script.nameOrSourceURL();
     } else if (this.type_ == Debug.ScriptBreakPointType.ScriptRegExp) {
       return this.script_regexp_object_.test(script.nameOrSourceURL());
-    } else { 
+    } else {
       throw new Error("Unexpected breakpoint type " + this.type_);
     }
   }
@@ -1579,7 +1579,7 @@
     response.failed('Missing argument "type" or "target"');
     return;
   }
-  
+
   // Either function or script break point.
   var break_point_number;
   if (type == 'function') {
@@ -1623,10 +1623,10 @@
     break_point_number =
         Debug.setScriptBreakPointByName(target, line, column, condition,
                                         groupId);
-  } else if (type == 'scriptId') { 
+  } else if (type == 'scriptId') {
     break_point_number =
         Debug.setScriptBreakPointById(target, line, column, condition, groupId);
-  } else if (type == 'scriptRegExp') { 
+  } else if (type == 'scriptRegExp') {
     break_point_number =
         Debug.setScriptBreakPointByRegExp(target, line, column, condition,
                                           groupId);
@@ -1797,7 +1797,7 @@
       description.type = 'scriptRegExp';
       description.script_regexp = break_point.script_regexp_object().source;
     } else {
-      throw new Error("Internal error: Unexpected breakpoint type: " + break_point.type()); 
+      throw new Error("Internal error: Unexpected breakpoint type: " + break_point.type());
     }
     array.push(description);
   }
@@ -1838,7 +1838,7 @@
     enabled = !Debug.isBreakOnException();
   } else if (type == 'uncaught') {
     enabled = !Debug.isBreakOnUncaughtException();
-  }  
+  }
 
   // Pull out and check the 'enabled' argument if present:
   if (!IS_UNDEFINED(request.arguments.enabled)) {
@@ -2022,22 +2022,22 @@
   if (!IS_UNDEFINED(frame) && global) {
     return response.failed('Arguments "frame" and "global" are exclusive');
   }
-  
+
   var additional_context_object;
   if (additional_context) {
     additional_context_object = {};
     for (var i = 0; i < additional_context.length; i++) {
       var mapping = additional_context[i];
       if (!IS_STRING(mapping.name) || !IS_NUMBER(mapping.handle)) {
-        return response.failed("Context element #" + i + 
+        return response.failed("Context element #" + i +
             " must contain name:string and handle:number");
-      } 
+      }
       var context_value_mirror = LookupMirror(mapping.handle);
       if (!context_value_mirror) {
         return response.failed("Context object '" + mapping.name +
             "' #" + mapping.handle + "# not found");
       }
-      additional_context_object[mapping.name] = context_value_mirror.value(); 
+      additional_context_object[mapping.name] = context_value_mirror.value();
     }
   }
 
diff --git a/src/debug.cc b/src/debug.cc
index aecbb46..2d58ce1 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -169,7 +169,8 @@
       if ((code->is_inline_cache_stub() &&
            !code->is_binary_op_stub() &&
            !code->is_unary_op_stub() &&
-           !code->is_compare_ic_stub()) ||
+           !code->is_compare_ic_stub() &&
+           !code->is_to_boolean_ic_stub()) ||
           RelocInfo::IsConstructCall(rmode())) {
         break_point_++;
         return;
@@ -1964,7 +1965,7 @@
 
 
 Debugger::Debugger(Isolate* isolate)
-    : debugger_access_(OS::CreateMutex()),
+    : debugger_access_(isolate->debugger_access()),
       event_listener_(Handle<Object>()),
       event_listener_data_(Handle<Object>()),
       compiling_natives_(false),
@@ -1986,8 +1987,6 @@
 
 
 Debugger::~Debugger() {
-  delete debugger_access_;
-  debugger_access_ = 0;
   delete dispatch_handler_access_;
   dispatch_handler_access_ = 0;
   delete command_received_;
diff --git a/src/deoptimizer.cc b/src/deoptimizer.cc
index c90df45..94b2ff5 100644
--- a/src/deoptimizer.cc
+++ b/src/deoptimizer.cc
@@ -1187,11 +1187,11 @@
 
 
 int32_t TranslationIterator::Next() {
-  ASSERT(HasNext());
   // Run through the bytes until we reach one with a least significant
   // bit of zero (marks the end).
   uint32_t bits = 0;
   for (int i = 0; true; i += 7) {
+    ASSERT(HasNext());
     uint8_t next = buffer_->get(index_++);
     bits |= (next >> 1) << i;
     if ((next & 1) == 0) break;
@@ -1442,6 +1442,7 @@
   UNREACHABLE();
 }
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
 
 DeoptimizedFrameInfo::DeoptimizedFrameInfo(
     Deoptimizer* deoptimizer, int frame_index) {
@@ -1471,5 +1472,6 @@
   v->VisitPointers(expression_stack_, expression_stack_ + expression_count_);
 }
 
+#endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal
diff --git a/src/deoptimizer.h b/src/deoptimizer.h
index 9265905..8641261 100644
--- a/src/deoptimizer.h
+++ b/src/deoptimizer.h
@@ -317,7 +317,7 @@
 
   List<HeapNumberMaterializationDescriptor> deferred_heap_numbers_;
 
-  static int table_entry_size_;
+  static const int table_entry_size_;
 
   friend class FrameDescription;
   friend class DeoptimizingCodeListNode;
@@ -336,6 +336,10 @@
     return malloc(size + frame_size - kPointerSize);
   }
 
+  void operator delete(void* pointer, uint32_t frame_size) {
+    free(pointer);
+  }
+
   void operator delete(void* description) {
     free(description);
   }
@@ -497,9 +501,7 @@
 
   int32_t Next();
 
-  bool HasNext() const { return index_ >= 0; }
-
-  void Done() { index_ = -1; }
+  bool HasNext() const { return index_ < buffer_->length(); }
 
   void Skip(int n) {
     for (int i = 0; i < n; i++) Next();
diff --git a/src/disassembler.cc b/src/disassembler.cc
index 368c3a8..79076d6 100644
--- a/src/disassembler.cc
+++ b/src/disassembler.cc
@@ -97,14 +97,17 @@
 }
 
 
-static void DumpBuffer(FILE* f, char* buff) {
+static void DumpBuffer(FILE* f, StringBuilder* out) {
   if (f == NULL) {
-    PrintF("%s", buff);
+    PrintF("%s\n", out->Finalize());
   } else {
-    fprintf(f, "%s", buff);
+    fprintf(f, "%s\n", out->Finalize());
   }
+  out->Reset();
 }
 
+
+
 static const int kOutBufferSize = 2048 + String::kMaxShortPrintLength;
 static const int kRelocInfoPosition = 57;
 
@@ -119,6 +122,7 @@
 
   v8::internal::EmbeddedVector<char, 128> decode_buffer;
   v8::internal::EmbeddedVector<char, kOutBufferSize> out_buffer;
+  StringBuilder out(out_buffer.start(), out_buffer.length());
   byte* pc = begin;
   disasm::Disassembler d(converter);
   RelocIterator* it = NULL;
@@ -181,17 +185,12 @@
       }
     }
 
-    StringBuilder out(out_buffer.start(), out_buffer.length());
-
     // Comments.
     for (int i = 0; i < comments.length(); i++) {
-      out.AddFormatted("                  %s\n", comments[i]);
+      out.AddFormatted("                  %s", comments[i]);
+      DumpBuffer(f, &out);
     }
 
-    // Write out comments, resets outp so that we can format the next line.
-    DumpBuffer(f, out.Finalize());
-    out.Reset();
-
     // Instruction address and instruction offset.
     out.AddFormatted("%p  %4d  ", prev_pc, prev_pc - begin);
 
@@ -209,7 +208,7 @@
         out.AddPadding(' ', kRelocInfoPosition - out.position());
       } else {
         // Additional reloc infos are printed on separate lines.
-        out.AddFormatted("\n");
+        DumpBuffer(f, &out);
         out.AddPadding(' ', kRelocInfoPosition);
       }
 
@@ -299,9 +298,18 @@
         out.AddFormatted("    ;; %s", RelocInfo::RelocModeName(rmode));
       }
     }
-    out.AddString("\n");
-    DumpBuffer(f, out.Finalize());
-    out.Reset();
+    DumpBuffer(f, &out);
+  }
+
+  // Emit comments following the last instruction (if any).
+  if (it != NULL) {
+    for ( ; !it->done(); it->next()) {
+      if (RelocInfo::IsComment(it->rinfo()->rmode())) {
+        out.AddFormatted("                  %s",
+                         reinterpret_cast<const char*>(it->rinfo()->data()));
+        DumpBuffer(f, &out);
+      }
+    }
   }
 
   delete it;
diff --git a/src/elements.cc b/src/elements.cc
new file mode 100644
index 0000000..1afc5da
--- /dev/null
+++ b/src/elements.cc
@@ -0,0 +1,634 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "objects.h"
+#include "elements.h"
+#include "utils.h"
+
+namespace v8 {
+namespace internal {
+
+
+ElementsAccessor** ElementsAccessor::elements_accessors_;
+
+
+bool HasKey(FixedArray* array, Object* key) {
+  int len0 = array->length();
+  for (int i = 0; i < len0; i++) {
+    Object* element = array->get(i);
+    if (element->IsSmi() && element == key) return true;
+    if (element->IsString() &&
+        key->IsString() && String::cast(element)->Equals(String::cast(key))) {
+      return true;
+    }
+  }
+  return false;
+}
+
+
+// Base class for element handler implementations. Contains the
+// the common logic for objects with different ElementsKinds.
+// Subclasses must specialize method for which the element
+// implementation differs from the base class implementation.
+//
+// This class is intended to be used in the following way:
+//
+//   class SomeElementsAccessor :
+//       public ElementsAccessorBase<SomeElementsAccessor,
+//                                   BackingStoreClass> {
+//     ...
+//   }
+//
+// This is an example of the Curiously Recurring Template Pattern (see
+// http://en.wikipedia.org/wiki/Curiously_recurring_template_pattern).  We use
+// CRTP to guarantee aggressive compile time optimizations (i.e.  inlining and
+// specialization of SomeElementsAccessor methods).
+template <typename ElementsAccessorSubclass, typename BackingStoreClass>
+class ElementsAccessorBase : public ElementsAccessor {
+ protected:
+  ElementsAccessorBase() { }
+  virtual MaybeObject* Get(FixedArrayBase* backing_store,
+                           uint32_t key,
+                           JSObject* obj,
+                           Object* receiver) {
+    return ElementsAccessorSubclass::Get(
+        BackingStoreClass::cast(backing_store), key, obj, receiver);
+  }
+
+  static MaybeObject* Get(BackingStoreClass* backing_store,
+                          uint32_t key,
+                          JSObject* obj,
+                          Object* receiver) {
+    if (key < ElementsAccessorSubclass::GetCapacity(backing_store)) {
+      return backing_store->get(key);
+    }
+    return backing_store->GetHeap()->the_hole_value();
+  }
+
+  virtual MaybeObject* Delete(JSObject* obj,
+                              uint32_t key,
+                              JSReceiver::DeleteMode mode) = 0;
+
+  virtual MaybeObject* AddElementsToFixedArray(FixedArrayBase* from,
+                                               FixedArray* to,
+                                               JSObject* holder,
+                                               Object* receiver) {
+    int len0 = to->length();
+#ifdef DEBUG
+    if (FLAG_enable_slow_asserts) {
+      for (int i = 0; i < len0; i++) {
+        ASSERT(!to->get(i)->IsTheHole());
+      }
+    }
+#endif
+    BackingStoreClass* backing_store = BackingStoreClass::cast(from);
+    uint32_t len1 = ElementsAccessorSubclass::GetCapacity(backing_store);
+
+    // Optimize if 'other' is empty.
+    // We cannot optimize if 'this' is empty, as other may have holes.
+    if (len1 == 0) return to;
+
+    // Compute how many elements are not in other.
+    int extra = 0;
+    for (uint32_t y = 0; y < len1; y++) {
+      if (ElementsAccessorSubclass::HasElementAtIndex(backing_store,
+                                                      y,
+                                                      holder,
+                                                      receiver)) {
+        uint32_t key =
+            ElementsAccessorSubclass::GetKeyForIndex(backing_store, y);
+        MaybeObject* maybe_value =
+            ElementsAccessorSubclass::Get(backing_store, key, holder, receiver);
+        Object* value;
+        if (!maybe_value->ToObject(&value)) return maybe_value;
+        ASSERT(!value->IsTheHole());
+        if (!HasKey(to, value)) {
+          extra++;
+        }
+      }
+    }
+
+    if (extra == 0) return to;
+
+    // Allocate the result
+    FixedArray* result;
+    MaybeObject* maybe_obj =
+        backing_store->GetHeap()->AllocateFixedArray(len0 + extra);
+    if (!maybe_obj->To<FixedArray>(&result)) return maybe_obj;
+
+    // Fill in the content
+    {
+      AssertNoAllocation no_gc;
+      WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
+      for (int i = 0; i < len0; i++) {
+        Object* e = to->get(i);
+        ASSERT(e->IsString() || e->IsNumber());
+        result->set(i, e, mode);
+      }
+    }
+    // Fill in the extra values.
+    int index = 0;
+    for (uint32_t y = 0; y < len1; y++) {
+      if (ElementsAccessorSubclass::HasElementAtIndex(backing_store,
+                                                      y,
+                                                      holder,
+                                                      receiver)) {
+        uint32_t key =
+            ElementsAccessorSubclass::GetKeyForIndex(backing_store, y);
+        MaybeObject* maybe_value =
+            ElementsAccessorSubclass::Get(backing_store, key, holder, receiver);
+        Object* value;
+        if (!maybe_value->ToObject(&value)) return maybe_value;
+        if (!value->IsTheHole() && !HasKey(to, value)) {
+          result->set(len0 + index, value);
+          index++;
+        }
+      }
+    }
+    ASSERT(extra == index);
+    return result;
+  }
+
+ protected:
+  static uint32_t GetCapacity(BackingStoreClass* backing_store) {
+    return backing_store->length();
+  }
+
+  virtual uint32_t GetCapacity(FixedArrayBase* backing_store) {
+    return ElementsAccessorSubclass::GetCapacity(
+        BackingStoreClass::cast(backing_store));
+  }
+
+  static bool HasElementAtIndex(BackingStoreClass* backing_store,
+                                uint32_t index,
+                                JSObject* holder,
+                                Object* receiver) {
+    uint32_t key =
+        ElementsAccessorSubclass::GetKeyForIndex(backing_store, index);
+    MaybeObject* element = ElementsAccessorSubclass::Get(backing_store,
+                                                         key,
+                                                         holder,
+                                                         receiver);
+    return !element->IsTheHole();
+  }
+
+  virtual bool HasElementAtIndex(FixedArrayBase* backing_store,
+                                 uint32_t index,
+                                 JSObject* holder,
+                                 Object* receiver) {
+    return ElementsAccessorSubclass::HasElementAtIndex(
+        BackingStoreClass::cast(backing_store), index, holder, receiver);
+  }
+
+  static uint32_t GetKeyForIndex(BackingStoreClass* backing_store,
+                                 uint32_t index) {
+    return index;
+  }
+
+  virtual uint32_t GetKeyForIndex(FixedArrayBase* backing_store,
+                                              uint32_t index) {
+    return ElementsAccessorSubclass::GetKeyForIndex(
+        BackingStoreClass::cast(backing_store), index);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ElementsAccessorBase);
+};
+
+
+class FastElementsAccessor
+    : public ElementsAccessorBase<FastElementsAccessor, FixedArray> {
+ public:
+  static MaybeObject* DeleteCommon(JSObject* obj,
+                                   uint32_t key) {
+    ASSERT(obj->HasFastElements() || obj->HasFastArgumentsElements());
+    Heap* heap = obj->GetHeap();
+    FixedArray* backing_store = FixedArray::cast(obj->elements());
+    if (backing_store->map() == heap->non_strict_arguments_elements_map()) {
+      backing_store = FixedArray::cast(backing_store->get(1));
+    } else {
+      Object* writable;
+      MaybeObject* maybe = obj->EnsureWritableFastElements();
+      if (!maybe->ToObject(&writable)) return maybe;
+      backing_store = FixedArray::cast(writable);
+    }
+    uint32_t length = static_cast<uint32_t>(
+        obj->IsJSArray()
+        ? Smi::cast(JSArray::cast(obj)->length())->value()
+        : backing_store->length());
+    if (key < length) {
+      backing_store->set_the_hole(key);
+      // If an old space backing store is larger than a certain size and
+      // has too few used values, normalize it.
+      // To avoid doing the check on every delete we require at least
+      // one adjacent hole to the value being deleted.
+      Object* hole = heap->the_hole_value();
+      const int kMinLengthForSparsenessCheck = 64;
+      if (backing_store->length() >= kMinLengthForSparsenessCheck &&
+          !heap->InNewSpace(backing_store) &&
+          ((key > 0 && backing_store->get(key - 1) == hole) ||
+           (key + 1 < length && backing_store->get(key + 1) == hole))) {
+        int num_used = 0;
+        for (int i = 0; i < backing_store->length(); ++i) {
+          if (backing_store->get(i) != hole) ++num_used;
+          // Bail out early if more than 1/4 is used.
+          if (4 * num_used > backing_store->length()) break;
+        }
+        if (4 * num_used <= backing_store->length()) {
+          MaybeObject* result = obj->NormalizeElements();
+          if (result->IsFailure()) return result;
+        }
+      }
+    }
+    return heap->true_value();
+  }
+
+ protected:
+  virtual MaybeObject* Delete(JSObject* obj,
+                              uint32_t key,
+                              JSReceiver::DeleteMode mode) {
+    return DeleteCommon(obj, key);
+  }
+};
+
+
+class FastDoubleElementsAccessor
+    : public ElementsAccessorBase<FastDoubleElementsAccessor,
+                                  FixedDoubleArray> {
+ protected:
+  friend class ElementsAccessorBase<FastDoubleElementsAccessor,
+                                    FixedDoubleArray>;
+
+  virtual MaybeObject* Delete(JSObject* obj,
+                              uint32_t key,
+                              JSReceiver::DeleteMode mode) {
+    int length = obj->IsJSArray()
+        ? Smi::cast(JSArray::cast(obj)->length())->value()
+        : FixedDoubleArray::cast(obj->elements())->length();
+    if (key < static_cast<uint32_t>(length)) {
+      FixedDoubleArray::cast(obj->elements())->set_the_hole(key);
+    }
+    return obj->GetHeap()->true_value();
+  }
+
+  static bool HasElementAtIndex(FixedDoubleArray* backing_store,
+                                uint32_t index,
+                                JSObject* holder,
+                                Object* receiver) {
+    return !backing_store->is_the_hole(index);
+  }
+};
+
+
+// Super class for all external element arrays.
+template<typename ExternalElementsAccessorSubclass,
+         typename ExternalArray>
+class ExternalElementsAccessor
+    : public ElementsAccessorBase<ExternalElementsAccessorSubclass,
+                                  ExternalArray> {
+ protected:
+  friend class ElementsAccessorBase<ExternalElementsAccessorSubclass,
+                                    ExternalArray>;
+
+  static MaybeObject* Get(ExternalArray* backing_store,
+                          uint32_t key,
+                          JSObject* obj,
+                          Object* receiver) {
+    if (key < ExternalElementsAccessorSubclass::GetCapacity(backing_store)) {
+      return backing_store->get(key);
+    } else {
+      return backing_store->GetHeap()->undefined_value();
+    }
+  }
+
+  virtual MaybeObject* Delete(JSObject* obj,
+                              uint32_t key,
+                              JSReceiver::DeleteMode mode) {
+    // External arrays always ignore deletes.
+    return obj->GetHeap()->true_value();
+  }
+};
+
+
+class ExternalByteElementsAccessor
+    : public ExternalElementsAccessor<ExternalByteElementsAccessor,
+                                      ExternalByteArray> {
+};
+
+
+class ExternalUnsignedByteElementsAccessor
+    : public ExternalElementsAccessor<ExternalUnsignedByteElementsAccessor,
+                                      ExternalUnsignedByteArray> {
+};
+
+
+class ExternalShortElementsAccessor
+    : public ExternalElementsAccessor<ExternalShortElementsAccessor,
+                                      ExternalShortArray> {
+};
+
+
+class ExternalUnsignedShortElementsAccessor
+    : public ExternalElementsAccessor<ExternalUnsignedShortElementsAccessor,
+                                      ExternalUnsignedShortArray> {
+};
+
+
+class ExternalIntElementsAccessor
+    : public ExternalElementsAccessor<ExternalIntElementsAccessor,
+                                      ExternalIntArray> {
+};
+
+
+class ExternalUnsignedIntElementsAccessor
+    : public ExternalElementsAccessor<ExternalUnsignedIntElementsAccessor,
+                                      ExternalUnsignedIntArray> {
+};
+
+
+class ExternalFloatElementsAccessor
+    : public ExternalElementsAccessor<ExternalFloatElementsAccessor,
+                                      ExternalFloatArray> {
+};
+
+
+class ExternalDoubleElementsAccessor
+    : public ExternalElementsAccessor<ExternalDoubleElementsAccessor,
+                                      ExternalDoubleArray> {
+};
+
+
+class PixelElementsAccessor
+    : public ExternalElementsAccessor<PixelElementsAccessor,
+                                      ExternalPixelArray> {
+};
+
+
+class DictionaryElementsAccessor
+    : public ElementsAccessorBase<DictionaryElementsAccessor,
+                                  NumberDictionary> {
+ public:
+  static MaybeObject* DeleteCommon(JSObject* obj,
+                                   uint32_t key,
+                                   JSReceiver::DeleteMode mode) {
+    Isolate* isolate = obj->GetIsolate();
+    Heap* heap = isolate->heap();
+    FixedArray* backing_store = FixedArray::cast(obj->elements());
+    bool is_arguments =
+        (obj->GetElementsKind() == JSObject::NON_STRICT_ARGUMENTS_ELEMENTS);
+    if (is_arguments) {
+      backing_store = FixedArray::cast(backing_store->get(1));
+    }
+    NumberDictionary* dictionary = NumberDictionary::cast(backing_store);
+    int entry = dictionary->FindEntry(key);
+    if (entry != NumberDictionary::kNotFound) {
+      Object* result = dictionary->DeleteProperty(entry, mode);
+      if (result == heap->true_value()) {
+        MaybeObject* maybe_elements = dictionary->Shrink(key);
+        FixedArray* new_elements = NULL;
+        if (!maybe_elements->To(&new_elements)) {
+          return maybe_elements;
+        }
+        if (is_arguments) {
+          FixedArray::cast(obj->elements())->set(1, new_elements);
+        } else {
+          obj->set_elements(new_elements);
+        }
+      }
+      if (mode == JSObject::STRICT_DELETION &&
+          result == heap->false_value()) {
+        // In strict mode, attempting to delete a non-configurable property
+        // throws an exception.
+        HandleScope scope(isolate);
+        Handle<Object> holder(obj);
+        Handle<Object> name = isolate->factory()->NewNumberFromUint(key);
+        Handle<Object> args[2] = { name, holder };
+        Handle<Object> error =
+            isolate->factory()->NewTypeError("strict_delete_property",
+                                             HandleVector(args, 2));
+        return isolate->Throw(*error);
+      }
+    }
+    return heap->true_value();
+  }
+
+ protected:
+  friend class ElementsAccessorBase<DictionaryElementsAccessor,
+                                    NumberDictionary>;
+
+  virtual MaybeObject* Delete(JSObject* obj,
+                              uint32_t key,
+                              JSReceiver::DeleteMode mode) {
+    return DeleteCommon(obj, key, mode);
+  }
+
+  static MaybeObject* Get(NumberDictionary* backing_store,
+                          uint32_t key,
+                          JSObject* obj,
+                          Object* receiver) {
+    int entry = backing_store->FindEntry(key);
+    if (entry != NumberDictionary::kNotFound) {
+      Object* element = backing_store->ValueAt(entry);
+      PropertyDetails details = backing_store->DetailsAt(entry);
+      if (details.type() == CALLBACKS) {
+        return obj->GetElementWithCallback(receiver,
+                                           element,
+                                           key,
+                                           obj);
+      } else {
+        return element;
+      }
+    }
+    return obj->GetHeap()->the_hole_value();
+  }
+
+  static uint32_t GetKeyForIndex(NumberDictionary* dict,
+                                 uint32_t index) {
+    Object* key = dict->KeyAt(index);
+    return Smi::cast(key)->value();
+  }
+};
+
+
+class NonStrictArgumentsElementsAccessor
+    : public ElementsAccessorBase<NonStrictArgumentsElementsAccessor,
+                                  FixedArray> {
+ protected:
+  friend class ElementsAccessorBase<NonStrictArgumentsElementsAccessor,
+                                    FixedArray>;
+
+  static MaybeObject* Get(FixedArray* parameter_map,
+                          uint32_t key,
+                          JSObject* obj,
+                          Object* receiver) {
+    Object* probe = GetParameterMapArg(parameter_map, key);
+    if (!probe->IsTheHole()) {
+      Context* context = Context::cast(parameter_map->get(0));
+      int context_index = Smi::cast(probe)->value();
+      ASSERT(!context->get(context_index)->IsTheHole());
+      return context->get(context_index);
+    } else {
+      // Object is not mapped, defer to the arguments.
+      FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
+      return ElementsAccessor::ForArray(arguments)->Get(arguments,
+                                                        key,
+                                                        obj,
+                                                        receiver);
+    }
+  }
+
+  virtual MaybeObject* Delete(JSObject* obj,
+                              uint32_t key
+                              ,
+                              JSReceiver::DeleteMode mode) {
+    FixedArray* parameter_map = FixedArray::cast(obj->elements());
+    Object* probe = GetParameterMapArg(parameter_map, key);
+    if (!probe->IsTheHole()) {
+      // TODO(kmillikin): We could check if this was the last aliased
+      // parameter, and revert to normal elements in that case.  That
+      // would enable GC of the context.
+      parameter_map->set_the_hole(key + 2);
+    } else {
+      FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
+      if (arguments->IsDictionary()) {
+        return DictionaryElementsAccessor::DeleteCommon(obj, key, mode);
+      } else {
+        return FastElementsAccessor::DeleteCommon(obj, key);
+      }
+    }
+    return obj->GetHeap()->true_value();
+  }
+
+  static uint32_t GetCapacity(FixedArray* parameter_map) {
+    FixedArrayBase* arguments = FixedArrayBase::cast(parameter_map->get(1));
+    return Max(static_cast<uint32_t>(parameter_map->length() - 2),
+               ForArray(arguments)->GetCapacity(arguments));
+  }
+
+  static uint32_t GetKeyForIndex(FixedArray* dict,
+                                 uint32_t index) {
+    return index;
+  }
+
+  static bool HasElementAtIndex(FixedArray* parameter_map,
+                                uint32_t index,
+                                JSObject* holder,
+                                Object* receiver) {
+    Object* probe = GetParameterMapArg(parameter_map, index);
+    if (!probe->IsTheHole()) {
+      return true;
+    } else {
+      FixedArrayBase* arguments = FixedArrayBase::cast(parameter_map->get(1));
+      ElementsAccessor* accessor = ElementsAccessor::ForArray(arguments);
+      return !accessor->Get(arguments, index, holder, receiver)->IsTheHole();
+    }
+  }
+
+ private:
+  static Object* GetParameterMapArg(FixedArray* parameter_map,
+                                    uint32_t key) {
+    uint32_t length = parameter_map->length();
+    return key < (length - 2 )
+        ? parameter_map->get(key + 2)
+        : parameter_map->GetHeap()->the_hole_value();
+  }
+};
+
+
+ElementsAccessor* ElementsAccessor::ForArray(FixedArrayBase* array) {
+  switch (array->map()->instance_type()) {
+    case FIXED_ARRAY_TYPE:
+      if (array->IsDictionary()) {
+        return elements_accessors_[JSObject::DICTIONARY_ELEMENTS];
+      } else {
+        return elements_accessors_[JSObject::FAST_ELEMENTS];
+      }
+    case EXTERNAL_BYTE_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_BYTE_ELEMENTS];
+    case EXTERNAL_UNSIGNED_BYTE_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS];
+    case EXTERNAL_SHORT_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_SHORT_ELEMENTS];
+    case EXTERNAL_UNSIGNED_SHORT_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS];
+    case EXTERNAL_INT_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_INT_ELEMENTS];
+    case EXTERNAL_UNSIGNED_INT_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS];
+    case EXTERNAL_FLOAT_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_FLOAT_ELEMENTS];
+    case EXTERNAL_DOUBLE_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_DOUBLE_ELEMENTS];
+    case EXTERNAL_PIXEL_ARRAY_TYPE:
+      return elements_accessors_[JSObject::EXTERNAL_PIXEL_ELEMENTS];
+    default:
+      UNREACHABLE();
+      return NULL;
+  }
+}
+
+
+void ElementsAccessor::InitializeOncePerProcess() {
+  static struct ConcreteElementsAccessors {
+    FastElementsAccessor fast_elements_handler;
+    FastDoubleElementsAccessor fast_double_elements_handler;
+    DictionaryElementsAccessor dictionary_elements_handler;
+    NonStrictArgumentsElementsAccessor non_strict_arguments_elements_handler;
+    ExternalByteElementsAccessor byte_elements_handler;
+    ExternalUnsignedByteElementsAccessor unsigned_byte_elements_handler;
+    ExternalShortElementsAccessor short_elements_handler;
+    ExternalUnsignedShortElementsAccessor unsigned_short_elements_handler;
+    ExternalIntElementsAccessor int_elements_handler;
+    ExternalUnsignedIntElementsAccessor unsigned_int_elements_handler;
+    ExternalFloatElementsAccessor float_elements_handler;
+    ExternalDoubleElementsAccessor double_elements_handler;
+    PixelElementsAccessor pixel_elements_handler;
+  } element_accessors;
+
+  static ElementsAccessor* accessor_array[] = {
+    &element_accessors.fast_elements_handler,
+    &element_accessors.fast_double_elements_handler,
+    &element_accessors.dictionary_elements_handler,
+    &element_accessors.non_strict_arguments_elements_handler,
+    &element_accessors.byte_elements_handler,
+    &element_accessors.unsigned_byte_elements_handler,
+    &element_accessors.short_elements_handler,
+    &element_accessors.unsigned_short_elements_handler,
+    &element_accessors.int_elements_handler,
+    &element_accessors.unsigned_int_elements_handler,
+    &element_accessors.float_elements_handler,
+    &element_accessors.double_elements_handler,
+    &element_accessors.pixel_elements_handler
+  };
+
+  elements_accessors_ = accessor_array;
+}
+
+
+} }  // namespace v8::internal
diff --git a/src/elements.h b/src/elements.h
new file mode 100644
index 0000000..3eae303
--- /dev/null
+++ b/src/elements.h
@@ -0,0 +1,95 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_ELEMENTS_H_
+#define V8_ELEMENTS_H_
+
+#include "objects.h"
+
+namespace v8 {
+namespace internal {
+
+// Abstract base class for handles that can operate on objects with differing
+// ElementsKinds.
+class ElementsAccessor {
+ public:
+  ElementsAccessor() { }
+  virtual ~ElementsAccessor() { }
+  virtual MaybeObject* Get(FixedArrayBase* backing_store,
+                           uint32_t key,
+                           JSObject* holder,
+                           Object* receiver) = 0;
+
+  virtual MaybeObject* Delete(JSObject* holder,
+                              uint32_t key,
+                              JSReceiver::DeleteMode mode) = 0;
+
+  virtual MaybeObject* AddElementsToFixedArray(FixedArrayBase* from,
+                                               FixedArray* to,
+                                               JSObject* holder,
+                                               Object* receiver) = 0;
+
+  // Returns a shared ElementsAccessor for the specified ElementsKind.
+  static ElementsAccessor* ForKind(JSObject::ElementsKind elements_kind) {
+    ASSERT(elements_kind < JSObject::kElementsKindCount);
+    return elements_accessors_[elements_kind];
+  }
+
+  static ElementsAccessor* ForArray(FixedArrayBase* array);
+
+  static void InitializeOncePerProcess();
+
+ protected:
+  friend class NonStrictArgumentsElementsAccessor;
+
+  virtual uint32_t GetCapacity(FixedArrayBase* backing_store) = 0;
+
+  virtual bool HasElementAtIndex(FixedArrayBase* backing_store,
+                                 uint32_t index,
+                                 JSObject* holder,
+                                 Object* receiver) = 0;
+
+  // Element handlers distinguish between indexes and keys when the manipulate
+  // elements.  Indexes refer to elements in terms of their location in the
+  // underlying storage's backing store representation, and are between 0
+  // GetCapacity.  Keys refer to elements in terms of the value that would be
+  // specific in JavaScript to access the element. In most implementations, keys
+  // are equivalent to indexes, and GetKeyForIndex returns the same value it is
+  // passed. In the NumberDictionary ElementsAccessor, GetKeyForIndex maps the
+  // index to a key using the KeyAt method on the NumberDictionary.
+  virtual uint32_t GetKeyForIndex(FixedArrayBase* backing_store,
+                                  uint32_t index) = 0;
+
+ private:
+  static ElementsAccessor** elements_accessors_;
+
+  DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_ELEMENTS_H_
diff --git a/src/execution.cc b/src/execution.cc
index 6ab73e7..bdbdca8 100644
--- a/src/execution.cc
+++ b/src/execution.cc
@@ -132,7 +132,7 @@
   if (*has_pending_exception) {
     isolate->ReportPendingMessages();
     if (isolate->pending_exception() == Failure::OutOfMemoryException()) {
-      if (!isolate->handle_scope_implementer()->ignore_out_of_memory()) {
+      if (!isolate->ignore_out_of_memory()) {
         V8::FatalProcessOutOfMemory("JS", true);
       }
     }
diff --git a/src/extensions/experimental/datetime-format.cc b/src/extensions/experimental/datetime-format.cc
index 7f46302..94a29ac 100644
--- a/src/extensions/experimental/datetime-format.cc
+++ b/src/extensions/experimental/datetime-format.cc
@@ -135,7 +135,7 @@
 v8::Handle<v8::Value> DateTimeFormat::GetWeekdays(const v8::Arguments& args) {
   icu::SimpleDateFormat* date_format = UnpackDateTimeFormat(args.Holder());
   if (!date_format) {
-    ThrowUnexpectedObjectError();
+    return ThrowUnexpectedObjectError();
   }
 
   const icu::DateFormatSymbols* symbols = date_format->getDateFormatSymbols();
diff --git a/src/extensions/experimental/number-format.cc b/src/extensions/experimental/number-format.cc
index 51e0b95..2932c52 100644
--- a/src/extensions/experimental/number-format.cc
+++ b/src/extensions/experimental/number-format.cc
@@ -36,6 +36,8 @@
 #include "unicode/numfmt.h"
 #include "unicode/uchar.h"
 #include "unicode/ucurr.h"
+#include "unicode/unum.h"
+#include "unicode/uversion.h"
 
 namespace v8 {
 namespace internal {
@@ -231,6 +233,8 @@
 }
 
 // Generates ICU number format pattern from given skeleton.
+// TODO(cira): Remove once ICU includes equivalent method
+// (see http://bugs.icu-project.org/trac/ticket/8610).
 static icu::DecimalFormat* CreateFormatterFromSkeleton(
     const icu::Locale& icu_locale,
     const icu::UnicodeString& skeleton,
@@ -251,6 +255,7 @@
     // Case of non-consecutive U+00A4 is taken care of in i18n.js.
     int32_t end_index = skeleton.lastIndexOf(currency_symbol, index);
 
+#if (U_ICU_VERSION_MAJOR_NUM == 4) && (U_ICU_VERSION_MINOR_NUM <= 6)
     icu::NumberFormat::EStyles style;
     switch (end_index - index) {
       case 0:
@@ -262,6 +267,19 @@
       default:
         style = icu::NumberFormat::kPluralCurrencyStyle;
     }
+#else  // ICU version is 4.8 or above (we ignore versions below 4.0).
+    UNumberFormatStyle style;
+    switch (end_index - index) {
+      case 0:
+        style = UNUM_CURRENCY;
+        break;
+      case 1:
+        style = UNUM_CURRENCY_ISO;
+        break;
+      default:
+        style = UNUM_CURRENCY_PLURAL;
+    }
+#endif
 
     base_format = static_cast<icu::DecimalFormat*>(
         icu::NumberFormat::createInstance(icu_locale, style, *status));
diff --git a/src/factory.cc b/src/factory.cc
index ac96668..ee5c37b 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -34,6 +34,7 @@
 #include "macro-assembler.h"
 #include "objects.h"
 #include "objects-visiting.h"
+#include "scopeinfo.h"
 
 namespace v8 {
 namespace internal {
@@ -84,6 +85,14 @@
 }
 
 
+Handle<ObjectHashTable> Factory::NewObjectHashTable(int at_least_space_for) {
+  ASSERT(0 <= at_least_space_for);
+  CALL_HEAP_FUNCTION(isolate(),
+                     ObjectHashTable::Allocate(at_least_space_for),
+                     ObjectHashTable);
+}
+
+
 Handle<DescriptorArray> Factory::NewDescriptorArray(int number_of_descriptors) {
   ASSERT(0 <= number_of_descriptors);
   CALL_HEAP_FUNCTION(isolate(),
@@ -283,6 +292,19 @@
 }
 
 
+Handle<Context> Factory::NewBlockContext(
+    Handle<JSFunction> function,
+    Handle<Context> previous,
+    Handle<SerializedScopeInfo> scope_info) {
+  CALL_HEAP_FUNCTION(
+      isolate(),
+      isolate()->heap()->AllocateBlockContext(*function,
+                                              *previous,
+                                              *scope_info),
+      Context);
+}
+
+
 Handle<Struct> Factory::NewStruct(InstanceType type) {
   CALL_HEAP_FUNCTION(
       isolate(),
@@ -726,6 +748,14 @@
 }
 
 
+Handle<SerializedScopeInfo> Factory::NewSerializedScopeInfo(int length) {
+  CALL_HEAP_FUNCTION(
+      isolate(),
+      isolate()->heap()->AllocateSerializedScopeInfo(length),
+      SerializedScopeInfo);
+}
+
+
 Handle<Code> Factory::NewCode(const CodeDesc& desc,
                               Code::Flags flags,
                               Handle<Object> self_ref,
diff --git a/src/factory.h b/src/factory.h
index 19f3827..a69b05b 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -58,6 +58,8 @@
 
   Handle<StringDictionary> NewStringDictionary(int at_least_space_for);
 
+  Handle<ObjectHashTable> NewObjectHashTable(int at_least_space_for);
+
   Handle<DescriptorArray> NewDescriptorArray(int number_of_descriptors);
   Handle<DeoptimizationInputData> NewDeoptimizationInputData(
       int deopt_entry_count,
@@ -165,6 +167,11 @@
                                  Handle<Context> previous,
                                  Handle<JSObject> extension);
 
+  // Create a 'block' context.
+  Handle<Context> NewBlockContext(Handle<JSFunction> function,
+                                  Handle<Context> previous,
+                                  Handle<SerializedScopeInfo> scope_info);
+
   // Return the Symbol matching the passed in string.
   Handle<String> SymbolFromString(Handle<String> value);
 
@@ -275,6 +282,8 @@
       Handle<Context> context,
       PretenureFlag pretenure = TENURED);
 
+  Handle<SerializedScopeInfo> NewSerializedScopeInfo(int length);
+
   Handle<Code> NewCode(const CodeDesc& desc,
                        Code::Flags flags,
                        Handle<Object> self_reference,
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index 2db44c3..7df2b0b 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -97,10 +97,14 @@
 #define FLAG FLAG_FULL
 
 // Flags for experimental language features.
+DEFINE_bool(harmony_typeof, false, "enable harmony semantics for typeof")
 DEFINE_bool(harmony_proxies, false, "enable harmony proxies")
+DEFINE_bool(harmony_weakmaps, false, "enable harmony weak maps")
+DEFINE_bool(harmony_block_scoping, false, "enable harmony block scoping")
 
 // Flags for experimental implementation features.
-DEFINE_bool(unbox_double_arrays, false, "automatically unbox arrays of doubles")
+DEFINE_bool(unbox_double_arrays, true, "automatically unbox arrays of doubles")
+DEFINE_bool(string_slices, false, "use string slices")
 
 // Flags for Crankshaft.
 #ifdef V8_TARGET_ARCH_MIPS
@@ -400,6 +404,7 @@
 DEFINE_bool(print_builtin_json_ast, false,
             "print source AST for builtins as JSON")
 DEFINE_string(stop_at, "", "function name where to insert a breakpoint")
+DEFINE_bool(verify_stack_height, false, "verify stack height tracing on ia32")
 
 // compiler.cc
 DEFINE_bool(print_builtin_scopes, false, "print scopes for builtins")
diff --git a/src/frames-inl.h b/src/frames-inl.h
index 5951806..7ba79bf 100644
--- a/src/frames-inl.h
+++ b/src/frames-inl.h
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -67,6 +67,7 @@
 
 
 inline void StackHandler::Iterate(ObjectVisitor* v, Code* holder) const {
+  v->VisitPointer(context_address());
   StackFrame::IteratePc(v, pc_address(), holder);
 }
 
@@ -82,6 +83,12 @@
 }
 
 
+inline Object** StackHandler::context_address() const {
+  const int offset = StackHandlerConstants::kContextOffset;
+  return reinterpret_cast<Object**>(address() + offset);
+}
+
+
 inline Address* StackHandler::pc_address() const {
   const int offset = StackHandlerConstants::kPCOffset;
   return reinterpret_cast<Address*>(address() + offset);
diff --git a/src/frames.h b/src/frames.h
index f542a92..4f94ebc 100644
--- a/src/frames.h
+++ b/src/frames.h
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -114,6 +114,7 @@
   // Accessors.
   inline State state() const;
 
+  inline Object** context_address() const;
   inline Address* pc_address() const;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(StackHandler);
diff --git a/src/full-codegen.cc b/src/full-codegen.cc
index 8c2f0d1..ca2026b 100644
--- a/src/full-codegen.cc
+++ b/src/full-codegen.cc
@@ -35,6 +35,7 @@
 #include "macro-assembler.h"
 #include "prettyprinter.h"
 #include "scopes.h"
+#include "scopeinfo.h"
 #include "stub-cache.h"
 
 namespace v8 {
@@ -90,8 +91,7 @@
 }
 
 
-void BreakableStatementChecker::VisitEnterWithContextStatement(
-    EnterWithContextStatement* stmt) {
+void BreakableStatementChecker::VisitWithStatement(WithStatement* stmt) {
   Visit(stmt->expression());
 }
 
@@ -317,7 +317,6 @@
   // field, and then a sequence of entries.  Each entry is a pair of AST id
   // and code-relative pc offset.
   masm()->Align(kIntSize);
-  masm()->RecordComment("[ Stack check table");
   unsigned offset = masm()->pc_offset();
   unsigned length = stack_checks_.length();
   __ dd(length);
@@ -325,7 +324,6 @@
     __ dd(stack_checks_[i].id);
     __ dd(stack_checks_[i].pc_and_state);
   }
-  masm()->RecordComment("]");
   return offset;
 }
 
@@ -437,6 +435,7 @@
 
 void FullCodeGenerator::StackValueContext::Plug(Register reg) const {
   __ push(reg);
+  codegen()->increment_stack_height();
 }
 
 
@@ -450,11 +449,13 @@
 
 void FullCodeGenerator::EffectContext::PlugTOS() const {
   __ Drop(1);
+  codegen()->decrement_stack_height();
 }
 
 
 void FullCodeGenerator::AccumulatorValueContext::PlugTOS() const {
   __ pop(result_register());
+  codegen()->decrement_stack_height();
 }
 
 
@@ -465,6 +466,7 @@
 void FullCodeGenerator::TestContext::PlugTOS() const {
   // For simplicity we always test the accumulator register.
   __ pop(result_register());
+  codegen()->decrement_stack_height();
   codegen()->PrepareForBailoutBeforeSplit(TOS_REG, false, NULL, NULL);
   codegen()->DoTest(this);
 }
@@ -843,9 +845,24 @@
   Breakable nested_statement(this, stmt);
   SetStatementPosition(stmt);
 
+  Scope* saved_scope = scope();
+  if (stmt->block_scope() != NULL) {
+    { Comment cmnt(masm_, "[ Extend block context");
+      scope_ = stmt->block_scope();
+      __ Push(scope_->GetSerializedScopeInfo());
+      PushFunctionArgumentForContextAllocation();
+      __ CallRuntime(Runtime::kPushBlockContext, 2);
+      StoreToFrameField(StandardFrameConstants::kContextOffset,
+                        context_register());
+    }
+    { Comment cmnt(masm_, "[ Declarations");
+      VisitDeclarations(scope_->declarations());
+    }
+  }
   PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
   VisitStatements(stmt->statements());
-  __ bind(nested_statement.break_target());
+  scope_ = saved_scope;
+  __ bind(nested_statement.break_label());
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
 }
 
@@ -896,19 +913,26 @@
   SetStatementPosition(stmt);
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  int context_length = 0;
   // When continuing, we clobber the unpredictable value in the accumulator
   // with one that's safe for GC.  If we hit an exit from the try block of
   // try...finally on our way out, we will unconditionally preserve the
   // accumulator on the stack.
   ClearAccumulator();
   while (!current->IsContinueTarget(stmt->target())) {
-    stack_depth = current->Exit(stack_depth);
-    current = current->outer();
+    current = current->Exit(&stack_depth, &context_length);
   }
   __ Drop(stack_depth);
+  if (context_length > 0) {
+    while (context_length > 0) {
+      LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+      --context_length;
+    }
+    StoreToFrameField(StandardFrameConstants::kContextOffset,
+                      context_register());
+  }
 
-  Iteration* loop = current->AsIteration();
-  __ jmp(loop->continue_target());
+  __ jmp(current->AsIteration()->continue_label());
 }
 
 
@@ -917,19 +941,26 @@
   SetStatementPosition(stmt);
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  int context_length = 0;
   // When breaking, we clobber the unpredictable value in the accumulator
   // with one that's safe for GC.  If we hit an exit from the try block of
   // try...finally on our way out, we will unconditionally preserve the
   // accumulator on the stack.
   ClearAccumulator();
   while (!current->IsBreakTarget(stmt->target())) {
-    stack_depth = current->Exit(stack_depth);
-    current = current->outer();
+    current = current->Exit(&stack_depth, &context_length);
   }
   __ Drop(stack_depth);
+  if (context_length > 0) {
+    while (context_length > 0) {
+      LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+      --context_length;
+    }
+    StoreToFrameField(StandardFrameConstants::kContextOffset,
+                      context_register());
+  }
 
-  Breakable* target = current->AsBreakable();
-  __ jmp(target->break_target());
+  __ jmp(current->AsBreakable()->break_label());
 }
 
 
@@ -942,9 +973,9 @@
   // Exit all nested statements.
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  int context_length = 0;
   while (current != NULL) {
-    stack_depth = current->Exit(stack_depth);
-    current = current->outer();
+    current = current->Exit(&stack_depth, &context_length);
   }
   __ Drop(stack_depth);
 
@@ -952,14 +983,23 @@
 }
 
 
-void FullCodeGenerator::VisitEnterWithContextStatement(
-    EnterWithContextStatement* stmt) {
-  Comment cmnt(masm_, "[ EnterWithContextStatement");
+void FullCodeGenerator::VisitWithStatement(WithStatement* stmt) {
+  Comment cmnt(masm_, "[ WithStatement");
   SetStatementPosition(stmt);
 
   VisitForStackValue(stmt->expression());
   PushFunctionArgumentForContextAllocation();
   __ CallRuntime(Runtime::kPushWithContext, 2);
+  decrement_stack_height();
+  StoreToFrameField(StandardFrameConstants::kContextOffset, context_register());
+
+  { WithOrCatch body(this);
+    Visit(stmt->statement());
+  }
+
+  // Pop context.
+  LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+  // Update local stack frame context field.
   StoreToFrameField(StandardFrameConstants::kContextOffset, context_register());
 }
 
@@ -988,12 +1028,12 @@
 
   // Record the position of the do while condition and make sure it is
   // possible to break on the condition.
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   PrepareForBailoutForId(stmt->ContinueId(), NO_REGISTERS);
   SetExpressionPosition(stmt->cond(), stmt->condition_position());
   VisitForControl(stmt->cond(),
                   &stack_check,
-                  loop_statement.break_target(),
+                  loop_statement.break_label(),
                   &stack_check);
 
   // Check stack before looping.
@@ -1003,7 +1043,7 @@
   __ jmp(&body);
 
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   decrement_loop_depth();
 }
 
@@ -1024,7 +1064,7 @@
 
   // Emit the statement position here as this is where the while
   // statement code starts.
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   SetStatementPosition(stmt);
 
   // Check stack before looping.
@@ -1033,11 +1073,11 @@
   __ bind(&test);
   VisitForControl(stmt->cond(),
                   &body,
-                  loop_statement.break_target(),
-                  loop_statement.break_target());
+                  loop_statement.break_label(),
+                  loop_statement.break_label());
 
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   decrement_loop_depth();
 }
 
@@ -1060,7 +1100,7 @@
   Visit(stmt->body());
 
   PrepareForBailoutForId(stmt->ContinueId(), NO_REGISTERS);
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   SetStatementPosition(stmt);
   if (stmt->next() != NULL) {
     Visit(stmt->next());
@@ -1077,14 +1117,14 @@
   if (stmt->cond() != NULL) {
     VisitForControl(stmt->cond(),
                     &body,
-                    loop_statement.break_target(),
-                    loop_statement.break_target());
+                    loop_statement.break_label(),
+                    loop_statement.break_label());
   } else {
     __ jmp(&body);
   }
 
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   decrement_loop_depth();
 }
 
@@ -1102,7 +1142,7 @@
   // to introduce a new scope to bind the catch variable and to remove
   // that scope again afterwards.
 
-  Label try_handler_setup, catch_entry, done;
+  Label try_handler_setup, done;
   __ Call(&try_handler_setup);
   // Try handler code, exception in result register.
 
@@ -1119,17 +1159,22 @@
   Scope* saved_scope = scope();
   scope_ = stmt->scope();
   ASSERT(scope_->declarations()->is_empty());
-  Visit(stmt->catch_block());
+  { WithOrCatch body(this);
+    Visit(stmt->catch_block());
+  }
   scope_ = saved_scope;
   __ jmp(&done);
 
   // Try block code. Sets up the exception handler chain.
   __ bind(&try_handler_setup);
   {
-    TryCatch try_block(this, &catch_entry);
+    const int delta = StackHandlerConstants::kSize / kPointerSize;
+    TryCatch try_block(this);
     __ PushTryHandler(IN_JAVASCRIPT, TRY_CATCH_HANDLER);
+    increment_stack_height(delta);
     Visit(stmt->try_block());
     __ PopTryHandler();
+    decrement_stack_height(delta);
   }
   __ bind(&done);
 }
@@ -1161,6 +1206,7 @@
   // cooked before GC.
   Label finally_entry;
   Label try_handler_setup;
+  const int original_stack_height = stack_height();
 
   // Setup the try-handler chain. Use a call to
   // Jump to try-handler setup and try-block code. Use call to put try-handler
@@ -1169,9 +1215,9 @@
   // Try handler code. Return address of call is pushed on handler stack.
   {
     // This code is only executed during stack-handler traversal when an
-    // exception is thrown. The execption is in the result register, which
+    // exception is thrown. The exception is in the result register, which
     // is retained by the finally block.
-    // Call the finally block and then rethrow the exception.
+    // Call the finally block and then rethrow the exception if it returns.
     __ Call(&finally_entry);
     __ push(result_register());
     __ CallRuntime(Runtime::kReThrow, 1);
@@ -1182,6 +1228,7 @@
     // Finally block implementation.
     Finally finally_block(this);
     EnterFinallyBlock();
+    set_stack_height(original_stack_height + Finally::kElementCount);
     Visit(stmt->finally_block());
     ExitFinallyBlock();  // Return to the calling code.
   }
@@ -1189,10 +1236,13 @@
   __ bind(&try_handler_setup);
   {
     // Setup try handler (stack pointer registers).
+    const int delta = StackHandlerConstants::kSize / kPointerSize;
     TryFinally try_block(this, &finally_entry);
     __ PushTryHandler(IN_JAVASCRIPT, TRY_FINALLY_HANDLER);
+    set_stack_height(original_stack_height + delta);
     Visit(stmt->try_block());
     __ PopTryHandler();
+    set_stack_height(original_stack_height);
   }
   // Execute the finally block on the way out.  Clobber the unpredictable
   // value in the accumulator with one that's safe for GC.  The finally
@@ -1222,6 +1272,7 @@
   __ bind(&true_case);
   SetExpressionPosition(expr->then_expression(),
                         expr->then_expression_position());
+  int start_stack_height = stack_height();
   if (context()->IsTest()) {
     const TestContext* for_test = TestContext::cast(context());
     VisitForControl(expr->then_expression(),
@@ -1235,6 +1286,7 @@
 
   PrepareForBailoutForId(expr->ElseId(), NO_REGISTERS);
   __ bind(&false_case);
+  set_stack_height(start_stack_height);
   if (context()->IsTest()) ForwardBailoutToChild(expr);
   SetExpressionPosition(expr->else_expression(),
                         expr->else_expression_position());
@@ -1275,26 +1327,23 @@
 
 void FullCodeGenerator::VisitThrow(Throw* expr) {
   Comment cmnt(masm_, "[ Throw");
+  // Throw has no effect on the stack height or the current expression context.
+  // Usually the expression context is null, because throw is a statement.
   VisitForStackValue(expr->exception());
   __ CallRuntime(Runtime::kThrow, 1);
+  decrement_stack_height();
   // Never returns here.
 }
 
 
-int FullCodeGenerator::TryFinally::Exit(int stack_depth) {
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryCatch::Exit(
+    int* stack_depth,
+    int* context_length) {
   // The macros used here must preserve the result register.
-  __ Drop(stack_depth);
+  __ Drop(*stack_depth);
   __ PopTryHandler();
-  __ Call(finally_entry_);
-  return 0;
-}
-
-
-int FullCodeGenerator::TryCatch::Exit(int stack_depth) {
-  // The macros used here must preserve the result register.
-  __ Drop(stack_depth);
-  __ PopTryHandler();
-  return 0;
+  *stack_depth = 0;
+  return previous_;
 }
 
 
diff --git a/src/full-codegen.h b/src/full-codegen.h
index 6b174f7..0ed26a1 100644
--- a/src/full-codegen.h
+++ b/src/full-codegen.h
@@ -83,6 +83,7 @@
         scope_(NULL),
         nesting_stack_(NULL),
         loop_depth_(0),
+        stack_height_(0),
         context_(NULL),
         bailout_entries_(0),
         stack_checks_(2),  // There's always at least one.
@@ -110,10 +111,7 @@
  private:
   class Breakable;
   class Iteration;
-  class TryCatch;
-  class TryFinally;
-  class Finally;
-  class ForIn;
+
   class TestContext;
 
   class NestedStatement BASE_EMBEDDED {
@@ -131,134 +129,135 @@
 
     virtual Breakable* AsBreakable() { return NULL; }
     virtual Iteration* AsIteration() { return NULL; }
-    virtual TryCatch* AsTryCatch() { return NULL; }
-    virtual TryFinally* AsTryFinally() { return NULL; }
-    virtual Finally* AsFinally() { return NULL; }
-    virtual ForIn* AsForIn() { return NULL; }
 
     virtual bool IsContinueTarget(Statement* target) { return false; }
     virtual bool IsBreakTarget(Statement* target) { return false; }
 
-    // Generate code to leave the nested statement. This includes
-    // cleaning up any stack elements in use and restoring the
-    // stack to the expectations of the surrounding statements.
-    // Takes a number of stack elements currently on top of the
-    // nested statement's stack, and returns a number of stack
-    // elements left on top of the surrounding statement's stack.
-    // The generated code must preserve the result register (which
-    // contains the value in case of a return).
-    virtual int Exit(int stack_depth) {
-      // Default implementation for the case where there is
-      // nothing to clean up.
-      return stack_depth;
+    // Notify the statement that we are exiting it via break, continue, or
+    // return and give it a chance to generate cleanup code.  Return the
+    // next outer statement in the nesting stack.  We accumulate in
+    // *stack_depth the amount to drop the stack and in *context_length the
+    // number of context chain links to unwind as we traverse the nesting
+    // stack from an exit to its target.
+    virtual NestedStatement* Exit(int* stack_depth, int* context_length) {
+      return previous_;
     }
-    NestedStatement* outer() { return previous_; }
 
  protected:
     MacroAssembler* masm() { return codegen_->masm(); }
 
- private:
     FullCodeGenerator* codegen_;
     NestedStatement* previous_;
     DISALLOW_COPY_AND_ASSIGN(NestedStatement);
   };
 
+  // A breakable statement such as a block.
   class Breakable : public NestedStatement {
    public:
-    Breakable(FullCodeGenerator* codegen,
-              BreakableStatement* break_target)
-        : NestedStatement(codegen),
-          target_(break_target) {}
-    virtual ~Breakable() {}
-    virtual Breakable* AsBreakable() { return this; }
-    virtual bool IsBreakTarget(Statement* statement) {
-      return target_ == statement;
+    Breakable(FullCodeGenerator* codegen, BreakableStatement* statement)
+        : NestedStatement(codegen), statement_(statement) {
     }
-    BreakableStatement* statement() { return target_; }
-    Label* break_target() { return &break_target_label_; }
+    virtual ~Breakable() {}
+
+    virtual Breakable* AsBreakable() { return this; }
+    virtual bool IsBreakTarget(Statement* target) {
+      return statement() == target;
+    }
+
+    BreakableStatement* statement() { return statement_; }
+    Label* break_label() { return &break_label_; }
+
    private:
-    BreakableStatement* target_;
-    Label break_target_label_;
-    DISALLOW_COPY_AND_ASSIGN(Breakable);
+    BreakableStatement* statement_;
+    Label break_label_;
   };
 
+  // An iteration statement such as a while, for, or do loop.
   class Iteration : public Breakable {
    public:
-    Iteration(FullCodeGenerator* codegen,
-              IterationStatement* iteration_statement)
-        : Breakable(codegen, iteration_statement) {}
-    virtual ~Iteration() {}
-    virtual Iteration* AsIteration() { return this; }
-    virtual bool IsContinueTarget(Statement* statement) {
-      return this->statement() == statement;
+    Iteration(FullCodeGenerator* codegen, IterationStatement* statement)
+        : Breakable(codegen, statement) {
     }
-    Label* continue_target() { return &continue_target_label_; }
+    virtual ~Iteration() {}
+
+    virtual Iteration* AsIteration() { return this; }
+    virtual bool IsContinueTarget(Statement* target) {
+      return statement() == target;
+    }
+
+    Label* continue_label() { return &continue_label_; }
+
    private:
-    Label continue_target_label_;
-    DISALLOW_COPY_AND_ASSIGN(Iteration);
+    Label continue_label_;
   };
 
-  // The environment inside the try block of a try/catch statement.
+  // The try block of a try/catch statement.
   class TryCatch : public NestedStatement {
    public:
-    explicit TryCatch(FullCodeGenerator* codegen, Label* catch_entry)
-        : NestedStatement(codegen), catch_entry_(catch_entry) { }
+    explicit TryCatch(FullCodeGenerator* codegen) : NestedStatement(codegen) {
+    }
     virtual ~TryCatch() {}
-    virtual TryCatch* AsTryCatch() { return this; }
-    Label* catch_entry() { return catch_entry_; }
-    virtual int Exit(int stack_depth);
-   private:
-    Label* catch_entry_;
-    DISALLOW_COPY_AND_ASSIGN(TryCatch);
+
+    virtual NestedStatement* Exit(int* stack_depth, int* context_length);
   };
 
-  // The environment inside the try block of a try/finally statement.
+  // The try block of a try/finally statement.
   class TryFinally : public NestedStatement {
    public:
-    explicit TryFinally(FullCodeGenerator* codegen, Label* finally_entry)
-        : NestedStatement(codegen), finally_entry_(finally_entry) { }
+    TryFinally(FullCodeGenerator* codegen, Label* finally_entry)
+        : NestedStatement(codegen), finally_entry_(finally_entry) {
+    }
     virtual ~TryFinally() {}
-    virtual TryFinally* AsTryFinally() { return this; }
-    Label* finally_entry() { return finally_entry_; }
-    virtual int Exit(int stack_depth);
+
+    virtual NestedStatement* Exit(int* stack_depth, int* context_length);
+
    private:
     Label* finally_entry_;
-    DISALLOW_COPY_AND_ASSIGN(TryFinally);
   };
 
-  // A FinallyEnvironment represents being inside a finally block.
-  // Abnormal termination of the finally block needs to clean up
-  // the block's parameters from the stack.
+  // The finally block of a try/finally statement.
   class Finally : public NestedStatement {
    public:
+    static const int kElementCount = 2;
+
     explicit Finally(FullCodeGenerator* codegen) : NestedStatement(codegen) { }
     virtual ~Finally() {}
-    virtual Finally* AsFinally() { return this; }
-    virtual int Exit(int stack_depth) {
-      return stack_depth + kFinallyStackElementCount;
+
+    virtual NestedStatement* Exit(int* stack_depth, int* context_length) {
+      *stack_depth += kElementCount;
+      return previous_;
     }
-   private:
-    // Number of extra stack slots occupied during a finally block.
-    static const int kFinallyStackElementCount = 2;
-    DISALLOW_COPY_AND_ASSIGN(Finally);
   };
 
-  // A ForInEnvironment represents being inside a for-in loop.
-  // Abnormal termination of the for-in block needs to clean up
-  // the block's temporary storage from the stack.
+  // The body of a for/in loop.
   class ForIn : public Iteration {
    public:
-    ForIn(FullCodeGenerator* codegen,
-          ForInStatement* statement)
-        : Iteration(codegen, statement) { }
-    virtual ~ForIn() {}
-    virtual ForIn* AsForIn() { return this; }
-    virtual int Exit(int stack_depth) {
-      return stack_depth + kForInStackElementCount;
+    static const int kElementCount = 5;
+
+    ForIn(FullCodeGenerator* codegen, ForInStatement* statement)
+        : Iteration(codegen, statement) {
     }
-   private:
-    static const int kForInStackElementCount = 5;
-    DISALLOW_COPY_AND_ASSIGN(ForIn);
+    virtual ~ForIn() {}
+
+    virtual NestedStatement* Exit(int* stack_depth, int* context_length) {
+      *stack_depth += kElementCount;
+      return previous_;
+    }
+  };
+
+
+  // The body of a with or catch.
+  class WithOrCatch : public NestedStatement {
+   public:
+    explicit WithOrCatch(FullCodeGenerator* codegen)
+        : NestedStatement(codegen) {
+    }
+    virtual ~WithOrCatch() {}
+
+    virtual NestedStatement* Exit(int* stack_depth, int* context_length) {
+      ++(*context_length);
+      return previous_;
+    }
   };
 
   // The forward bailout stack keeps track of the expressions that can
@@ -519,6 +518,35 @@
     loop_depth_--;
   }
 
+#if defined(V8_TARGET_ARCH_IA32)
+  int stack_height() { return stack_height_; }
+  void set_stack_height(int depth) { stack_height_ = depth; }
+  void increment_stack_height() { stack_height_++; }
+  void increment_stack_height(int delta) { stack_height_ += delta; }
+  void decrement_stack_height() {
+    if (FLAG_verify_stack_height) {
+      ASSERT(stack_height_ > 0);
+    }
+    stack_height_--;
+  }
+  void decrement_stack_height(int delta) {
+    stack_height_-= delta;
+    if (FLAG_verify_stack_height) {
+      ASSERT(stack_height_ >= 0);
+    }
+  }
+  // Call this function only if FLAG_verify_stack_height is true.
+  void verify_stack_height();  // Generates a runtime check of esp - ebp.
+#else
+  int stack_height() { return 0; }
+  void set_stack_height(int depth) {}
+  void increment_stack_height() {}
+  void increment_stack_height(int delta) {}
+  void decrement_stack_height() {}
+  void decrement_stack_height(int delta) {}
+  void verify_stack_height() {}
+#endif  // V8_TARGET_ARCH_IA32
+
   MacroAssembler* masm() { return masm_; }
 
   class ExpressionContext;
@@ -578,6 +606,10 @@
 
     virtual ~ExpressionContext() {
       codegen_->set_new_context(old_);
+      if (FLAG_verify_stack_height) {
+        ASSERT_EQ(expected_stack_height_, codegen()->stack_height());
+        codegen()->verify_stack_height();
+      }
     }
 
     Isolate* isolate() const { return codegen_->isolate(); }
@@ -631,6 +663,7 @@
     FullCodeGenerator* codegen() const { return codegen_; }
     MacroAssembler* masm() const { return masm_; }
     MacroAssembler* masm_;
+    int expected_stack_height_;  // The expected stack height esp - ebp on exit.
 
    private:
     const ExpressionContext* old_;
@@ -640,7 +673,9 @@
   class AccumulatorValueContext : public ExpressionContext {
    public:
     explicit AccumulatorValueContext(FullCodeGenerator* codegen)
-        : ExpressionContext(codegen) { }
+        : ExpressionContext(codegen) {
+      expected_stack_height_ = codegen->stack_height();
+    }
 
     virtual void Plug(bool flag) const;
     virtual void Plug(Register reg) const;
@@ -661,7 +696,9 @@
   class StackValueContext : public ExpressionContext {
    public:
     explicit StackValueContext(FullCodeGenerator* codegen)
-        : ExpressionContext(codegen) { }
+        : ExpressionContext(codegen) {
+      expected_stack_height_ = codegen->stack_height() + 1;
+    }
 
     virtual void Plug(bool flag) const;
     virtual void Plug(Register reg) const;
@@ -690,7 +727,9 @@
           condition_(condition),
           true_label_(true_label),
           false_label_(false_label),
-          fall_through_(fall_through) { }
+          fall_through_(fall_through) {
+      expected_stack_height_ = codegen->stack_height();
+    }
 
     static const TestContext* cast(const ExpressionContext* context) {
       ASSERT(context->IsTest());
@@ -727,7 +766,10 @@
   class EffectContext : public ExpressionContext {
    public:
     explicit EffectContext(FullCodeGenerator* codegen)
-        : ExpressionContext(codegen) { }
+        : ExpressionContext(codegen) {
+      expected_stack_height_ = codegen->stack_height();
+    }
+
 
     virtual void Plug(bool flag) const;
     virtual void Plug(Register reg) const;
@@ -751,6 +793,7 @@
   Label return_label_;
   NestedStatement* nesting_stack_;
   int loop_depth_;
+  int stack_height_;
   const ExpressionContext* context_;
   ZoneList<BailoutEntry> bailout_entries_;
   ZoneList<BailoutEntry> stack_checks_;
diff --git a/src/func-name-inferrer.h b/src/func-name-inferrer.h
index bec3a5c..1a57268 100644
--- a/src/func-name-inferrer.h
+++ b/src/func-name-inferrer.h
@@ -70,6 +70,12 @@
     }
   }
 
+  void RemoveLastFunction() {
+    if (IsOpen() && !funcs_to_infer_.is_empty()) {
+      funcs_to_infer_.RemoveLast();
+    }
+  }
+
   // Infers a function name and leaves names collection state.
   void Infer() {
     ASSERT(IsOpen());
diff --git a/src/handles.cc b/src/handles.cc
index b03efbd..8c6439b 100644
--- a/src/handles.cc
+++ b/src/handles.cc
@@ -422,48 +422,18 @@
 
 
 Handle<Object> GetHiddenProperties(Handle<JSObject> obj,
-                                   bool create_if_needed) {
-  Isolate* isolate = obj->GetIsolate();
-  Object* holder = obj->BypassGlobalProxy();
-  if (holder->IsUndefined()) return isolate->factory()->undefined_value();
-  obj = Handle<JSObject>(JSObject::cast(holder), isolate);
+                                   JSObject::HiddenPropertiesFlag flag) {
+  CALL_HEAP_FUNCTION(obj->GetIsolate(),
+                     obj->GetHiddenProperties(flag),
+                     Object);
+}
 
-  if (obj->HasFastProperties()) {
-    // If the object has fast properties, check whether the first slot
-    // in the descriptor array matches the hidden symbol. Since the
-    // hidden symbols hash code is zero (and no other string has hash
-    // code zero) it will always occupy the first entry if present.
-    DescriptorArray* descriptors = obj->map()->instance_descriptors();
-    if ((descriptors->number_of_descriptors() > 0) &&
-        (descriptors->GetKey(0) == isolate->heap()->hidden_symbol()) &&
-        descriptors->IsProperty(0)) {
-      ASSERT(descriptors->GetType(0) == FIELD);
-      return Handle<Object>(obj->FastPropertyAt(descriptors->GetFieldIndex(0)),
-                            isolate);
-    }
-  }
 
-  // Only attempt to find the hidden properties in the local object and not
-  // in the prototype chain.  Note that HasLocalProperty() can cause a GC in
-  // the general case in the presence of interceptors.
-  if (!obj->HasHiddenPropertiesObject()) {
-    // Hidden properties object not found. Allocate a new hidden properties
-    // object if requested. Otherwise return the undefined value.
-    if (create_if_needed) {
-      Handle<Object> hidden_obj =
-          isolate->factory()->NewJSObject(isolate->object_function());
-
-      // Don't allow leakage of the hidden object through accessors
-      // on Object.prototype.
-      SetPrototype(Handle<JSObject>::cast(hidden_obj),
-                   isolate->factory()->null_value());
-      CALL_HEAP_FUNCTION(isolate,
-                         obj->SetHiddenPropertiesObject(*hidden_obj), Object);
-    } else {
-      return isolate->factory()->undefined_value();
-    }
-  }
-  return Handle<Object>(obj->GetHiddenPropertiesObject(), isolate);
+int GetIdentityHash(Handle<JSObject> obj) {
+  CALL_AND_RETRY(obj->GetIsolate(),
+                 obj->GetIdentityHash(JSObject::ALLOW_CREATION),
+                 return Smi::cast(__object__)->value(),
+                 return 0);
 }
 
 
@@ -647,15 +617,17 @@
   {
     AssertNoAllocation no_heap_allocation;  // ensure vectors stay valid.
     // Dispatch on type of strings.
-    if (src->IsAsciiRepresentation()) {
+    String::FlatContent content = src->GetFlatContent();
+    ASSERT(content.IsFlat());
+    if (content.IsAscii()) {
       CalculateLineEnds(isolate,
                         &line_ends,
-                        src->ToAsciiVector(),
+                        content.ToAsciiVector(),
                         with_last_line);
     } else {
       CalculateLineEnds(isolate,
                         &line_ends,
-                        src->ToUC16Vector(),
+                        content.ToUC16Vector(),
                         with_last_line);
     }
   }
@@ -913,6 +885,15 @@
 }
 
 
+Handle<ObjectHashTable> PutIntoObjectHashTable(Handle<ObjectHashTable> table,
+                                               Handle<JSObject> key,
+                                               Handle<Object> value) {
+  CALL_HEAP_FUNCTION(table->GetIsolate(),
+                     table->Put(*key, *value),
+                     ObjectHashTable);
+}
+
+
 bool EnsureCompiled(Handle<SharedFunctionInfo> shared,
                     ClearExceptionFlag flag) {
   return shared->is_compiled() || CompileLazyShared(shared, flag);
diff --git a/src/handles.h b/src/handles.h
index 13c6dd6..9bb3b1f 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -264,9 +264,13 @@
 Handle<Object> SetPrototype(Handle<JSObject> obj, Handle<Object> value);
 
 // Return the object's hidden properties object. If the object has no hidden
-// properties and create_if_needed is true, then a new hidden property object
-// will be allocated. Otherwise the Heap::undefined_value is returned.
-Handle<Object> GetHiddenProperties(Handle<JSObject> obj, bool create_if_needed);
+// properties and HiddenPropertiesFlag::ALLOW_CREATION is passed, then a new
+// hidden property object will be allocated. Otherwise Heap::undefined_value
+// is returned.
+Handle<Object> GetHiddenProperties(Handle<JSObject> obj,
+                                   JSObject::HiddenPropertiesFlag flag);
+
+int GetIdentityHash(Handle<JSObject> obj);
 
 Handle<Object> DeleteElement(Handle<JSObject> obj, uint32_t index);
 Handle<Object> DeleteProperty(Handle<JSObject> obj, Handle<String> prop);
@@ -343,6 +347,10 @@
 
 Handle<Object> PreventExtensions(Handle<JSObject> object);
 
+Handle<ObjectHashTable> PutIntoObjectHashTable(Handle<ObjectHashTable> table,
+                                               Handle<JSObject> key,
+                                               Handle<Object> value);
+
 // Does lazy compilation of the given function. Returns true on success and
 // false if the compilation resulted in a stack overflow.
 enum ClearExceptionFlag { KEEP_EXCEPTION, CLEAR_EXCEPTION };
diff --git a/src/heap-inl.h b/src/heap-inl.h
index b0b4fbe..7b666af 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -142,6 +142,11 @@
 }
 
 
+MaybeObject* Heap::CopyFixedDoubleArray(FixedDoubleArray* src) {
+  return CopyFixedDoubleArrayWithMap(src, src->map());
+}
+
+
 MaybeObject* Heap::AllocateRaw(int size_in_bytes,
                                AllocationSpace space,
                                AllocationSpace retry_space) {
@@ -318,10 +323,10 @@
   ASSERT(type != JS_GLOBAL_PROPERTY_CELL_TYPE);
 
   if (type < FIRST_NONSTRING_TYPE) {
-    // There are three string representations: sequential strings, cons
-    // strings, and external strings.  Only cons strings contain
-    // non-map-word pointers to heap objects.
-    return ((type & kStringRepresentationMask) == kConsStringTag)
+    // There are four string representations: sequential strings, external
+    // strings, cons strings, and sliced strings.
+    // Only the latter two contain non-map-word pointers to heap objects.
+    return ((type & kIsIndirectStringMask) == kIsIndirectStringTag)
         ? OLD_POINTER_SPACE
         : OLD_DATA_SPACE;
   } else {
diff --git a/src/heap.cc b/src/heap.cc
index 2d27570..279f30b 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -438,7 +438,9 @@
 #if defined(DEBUG)
   ReportStatisticsAfterGC();
 #endif  // DEBUG
+#ifdef ENABLE_DEBUGGER_SUPPORT
   isolate_->debug()->AfterGarbageCollection();
+#endif  // ENABLE_DEBUGGER_SUPPORT
 }
 
 
@@ -1288,10 +1290,18 @@
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
                         template VisitSpecialized<ConsString::kSize>);
 
+    table_.Register(kVisitSlicedString,
+                    &ObjectEvacuationStrategy<POINTER_OBJECT>::
+                        template VisitSpecialized<SlicedString::kSize>);
+
     table_.Register(kVisitSharedFunctionInfo,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
                         template VisitSpecialized<SharedFunctionInfo::kSize>);
 
+    table_.Register(kVisitJSWeakMap,
+                    &ObjectEvacuationStrategy<POINTER_OBJECT>::
+                    Visit);
+
     table_.Register(kVisitJSRegExp,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
                     Visit);
@@ -1739,6 +1749,12 @@
   set_fixed_cow_array_map(Map::cast(obj));
   ASSERT(fixed_array_map() != fixed_cow_array_map());
 
+  { MaybeObject* maybe_obj =
+        AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
+    if (!maybe_obj->ToObject(&obj)) return false;
+  }
+  set_serialized_scope_info_map(Map::cast(obj));
+
   { MaybeObject* maybe_obj = AllocateMap(HEAP_NUMBER_TYPE, HeapNumber::kSize);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
@@ -1904,6 +1920,12 @@
         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
+  set_block_context_map(Map::cast(obj));
+
+  { MaybeObject* maybe_obj =
+        AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
+    if (!maybe_obj->ToObject(&obj)) return false;
+  }
   Map* global_context_map = Map::cast(obj);
   global_context_map->set_visitor_id(StaticVisitorBase::kVisitGlobalContext);
   set_global_context_map(global_context_map);
@@ -2546,6 +2568,8 @@
 
   // If the resulting string is small make a flat string.
   if (length < String::kMinNonFlatLength) {
+    // Note that neither of the two inputs can be a slice because:
+    STATIC_ASSERT(String::kMinNonFlatLength <= SlicedString::kMinLength);
     ASSERT(first->IsFlat());
     ASSERT(second->IsFlat());
     if (is_ascii) {
@@ -2637,24 +2661,69 @@
   // Make an attempt to flatten the buffer to reduce access time.
   buffer = buffer->TryFlattenGetString();
 
-  Object* result;
-  { MaybeObject* maybe_result = buffer->IsAsciiRepresentation()
-                   ? AllocateRawAsciiString(length, pretenure )
-                   : AllocateRawTwoByteString(length, pretenure);
-    if (!maybe_result->ToObject(&result)) return maybe_result;
-  }
-  String* string_result = String::cast(result);
-  // Copy the characters into the new object.
-  if (buffer->IsAsciiRepresentation()) {
-    ASSERT(string_result->IsAsciiRepresentation());
-    char* dest = SeqAsciiString::cast(string_result)->GetChars();
-    String::WriteToFlat(buffer, dest, start, end);
-  } else {
-    ASSERT(string_result->IsTwoByteRepresentation());
-    uc16* dest = SeqTwoByteString::cast(string_result)->GetChars();
-    String::WriteToFlat(buffer, dest, start, end);
+  // TODO(1626): For now slicing external strings is not supported.  However,
+  // a flat cons string can have an external string as first part in some cases.
+  // Therefore we have to single out this case as well.
+  if (!FLAG_string_slices ||
+      (buffer->IsConsString() &&
+        (!buffer->IsFlat() ||
+         !ConsString::cast(buffer)->first()->IsSeqString())) ||
+      buffer->IsExternalString() ||
+      length < SlicedString::kMinLength ||
+      pretenure == TENURED) {
+    Object* result;
+    { MaybeObject* maybe_result = buffer->IsAsciiRepresentation()
+                     ? AllocateRawAsciiString(length, pretenure)
+                     : AllocateRawTwoByteString(length, pretenure);
+      if (!maybe_result->ToObject(&result)) return maybe_result;
+    }
+    String* string_result = String::cast(result);
+    // Copy the characters into the new object.
+    if (buffer->IsAsciiRepresentation()) {
+      ASSERT(string_result->IsAsciiRepresentation());
+      char* dest = SeqAsciiString::cast(string_result)->GetChars();
+      String::WriteToFlat(buffer, dest, start, end);
+    } else {
+      ASSERT(string_result->IsTwoByteRepresentation());
+      uc16* dest = SeqTwoByteString::cast(string_result)->GetChars();
+      String::WriteToFlat(buffer, dest, start, end);
+    }
+    return result;
   }
 
+  ASSERT(buffer->IsFlat());
+  ASSERT(!buffer->IsExternalString());
+#if DEBUG
+  buffer->StringVerify();
+#endif
+
+  Object* result;
+  { Map* map = buffer->IsAsciiRepresentation()
+                 ? sliced_ascii_string_map()
+                 : sliced_string_map();
+    MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
+    if (!maybe_result->ToObject(&result)) return maybe_result;
+  }
+
+  AssertNoAllocation no_gc;
+  SlicedString* sliced_string = SlicedString::cast(result);
+  sliced_string->set_length(length);
+  sliced_string->set_hash_field(String::kEmptyHashField);
+  if (buffer->IsConsString()) {
+    ConsString* cons = ConsString::cast(buffer);
+    ASSERT(cons->second()->length() == 0);
+    sliced_string->set_parent(cons->first());
+    sliced_string->set_offset(start);
+  } else if (buffer->IsSlicedString()) {
+    // Prevent nesting sliced strings.
+    SlicedString* parent_slice = SlicedString::cast(buffer);
+    sliced_string->set_parent(parent_slice->parent());
+    sliced_string->set_offset(start + parent_slice->offset());
+  } else {
+    sliced_string->set_parent(buffer);
+    sliced_string->set_offset(start);
+  }
+  ASSERT(sliced_string->parent()->IsSeqString());
   return result;
 }
 
@@ -3389,17 +3458,22 @@
               object_size);
   }
 
-  FixedArray* elements = FixedArray::cast(source->elements());
+  FixedArrayBase* elements = FixedArrayBase::cast(source->elements());
   FixedArray* properties = FixedArray::cast(source->properties());
   // Update elements if necessary.
   if (elements->length() > 0) {
     Object* elem;
-    { MaybeObject* maybe_elem =
-          (elements->map() == fixed_cow_array_map()) ?
-          elements : CopyFixedArray(elements);
+    { MaybeObject* maybe_elem;
+      if (elements->map() == fixed_cow_array_map()) {
+        maybe_elem = FixedArray::cast(elements);
+      } else if (source->HasFastDoubleElements()) {
+        maybe_elem = CopyFixedDoubleArray(FixedDoubleArray::cast(elements));
+      } else {
+        maybe_elem = CopyFixedArray(FixedArray::cast(elements));
+      }
       if (!maybe_elem->ToObject(&elem)) return maybe_elem;
     }
-    JSObject::cast(clone)->set_elements(FixedArray::cast(elem));
+    JSObject::cast(clone)->set_elements(FixedArrayBase::cast(elem));
   }
   // Update properties if necessary.
   if (properties->length() > 0) {
@@ -3758,6 +3832,23 @@
 }
 
 
+MaybeObject* Heap::CopyFixedDoubleArrayWithMap(FixedDoubleArray* src,
+                                               Map* map) {
+  int len = src->length();
+  Object* obj;
+  { MaybeObject* maybe_obj = AllocateRawFixedDoubleArray(len, NOT_TENURED);
+    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  }
+  HeapObject* dst = HeapObject::cast(obj);
+  dst->set_map(map);
+  CopyBlock(
+      dst->address() + FixedDoubleArray::kLengthOffset,
+      src->address() + FixedDoubleArray::kLengthOffset,
+      FixedDoubleArray::SizeFor(len) - FixedDoubleArray::kLengthOffset);
+  return obj;
+}
+
+
 MaybeObject* Heap::AllocateFixedArray(int length) {
   ASSERT(length >= 0);
   if (length == 0) return empty_fixed_array();
@@ -3989,6 +4080,36 @@
 }
 
 
+MaybeObject* Heap::AllocateBlockContext(JSFunction* function,
+                                        Context* previous,
+                                        SerializedScopeInfo* scope_info) {
+  Object* result;
+  { MaybeObject* maybe_result =
+        AllocateFixedArrayWithHoles(scope_info->NumberOfContextSlots());
+    if (!maybe_result->ToObject(&result)) return maybe_result;
+  }
+  Context* context = reinterpret_cast<Context*>(result);
+  context->set_map(block_context_map());
+  context->set_closure(function);
+  context->set_previous(previous);
+  context->set_extension(scope_info);
+  context->set_global(previous->global());
+  return context;
+}
+
+
+MaybeObject* Heap::AllocateSerializedScopeInfo(int length) {
+  Object* result;
+  { MaybeObject* maybe_result = AllocateFixedArray(length, TENURED);
+    if (!maybe_result->ToObject(&result)) return maybe_result;
+  }
+  SerializedScopeInfo* scope_info =
+      reinterpret_cast<SerializedScopeInfo*>(result);
+  scope_info->set_map(serialized_scope_info_map());
+  return scope_info;
+}
+
+
 MaybeObject* Heap::AllocateStruct(InstanceType type) {
   Map* map;
   switch (type) {
diff --git a/src/heap.h b/src/heap.h
index 6cd4f84..0f69fab 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -65,6 +65,7 @@
   V(Map, heap_number_map, HeapNumberMap)                                       \
   V(Map, global_context_map, GlobalContextMap)                                 \
   V(Map, fixed_array_map, FixedArrayMap)                                       \
+  V(Map, serialized_scope_info_map, SerializedScopeInfoMap)                    \
   V(Map, fixed_cow_array_map, FixedCOWArrayMap)                                \
   V(Map, fixed_double_array_map, FixedDoubleArrayMap)                          \
   V(Object, no_interceptor_result_sentinel, NoInterceptorResultSentinel)       \
@@ -87,6 +88,8 @@
   V(Map, symbol_map, SymbolMap)                                                \
   V(Map, cons_string_map, ConsStringMap)                                       \
   V(Map, cons_ascii_string_map, ConsAsciiStringMap)                            \
+  V(Map, sliced_string_map, SlicedStringMap)                                   \
+  V(Map, sliced_ascii_string_map, SlicedAsciiStringMap)                        \
   V(Map, ascii_symbol_map, AsciiSymbolMap)                                     \
   V(Map, cons_symbol_map, ConsSymbolMap)                                       \
   V(Map, cons_ascii_symbol_map, ConsAsciiSymbolMap)                            \
@@ -111,6 +114,7 @@
   V(Map, function_context_map, FunctionContextMap)                             \
   V(Map, catch_context_map, CatchContextMap)                                   \
   V(Map, with_context_map, WithContextMap)                                     \
+  V(Map, block_context_map, BlockContextMap)                                   \
   V(Map, code_map, CodeMap)                                                    \
   V(Map, oddball_map, OddballMap)                                              \
   V(Map, global_property_cell_map, GlobalPropertyCellMap)                      \
@@ -160,6 +164,7 @@
   V(length_symbol, "length")                                             \
   V(name_symbol, "name")                                                 \
   V(native_symbol, "native")                                             \
+  V(null_symbol, "null")                                                 \
   V(number_symbol, "number")                                             \
   V(Number_symbol, "Number")                                             \
   V(nan_symbol, "NaN")                                                   \
@@ -220,7 +225,8 @@
   V(closure_symbol, "(closure)")                                         \
   V(use_strict, "use strict")                                            \
   V(dot_symbol, ".")                                                     \
-  V(anonymous_function_symbol, "(anonymous function)")
+  V(anonymous_function_symbol, "(anonymous function)")                   \
+  V(block_scope_symbol, ".block")
 
 // Forward declarations.
 class GCTracer;
@@ -483,6 +489,9 @@
   // Allocates an empty code cache.
   MUST_USE_RESULT MaybeObject* AllocateCodeCache();
 
+  // Allocates a serialized scope info.
+  MUST_USE_RESULT MaybeObject* AllocateSerializedScopeInfo(int length);
+
   // Allocates an empty PolymorphicCodeCache.
   MUST_USE_RESULT MaybeObject* AllocatePolymorphicCodeCache();
 
@@ -617,6 +626,16 @@
   // Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
   MUST_USE_RESULT MaybeObject* CopyFixedArrayWithMap(FixedArray* src, Map* map);
 
+  // Make a copy of src and return it. Returns
+  // Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
+  MUST_USE_RESULT inline MaybeObject* CopyFixedDoubleArray(
+      FixedDoubleArray* src);
+
+  // Make a copy of src, set the map, and return the copy. Returns
+  // Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
+  MUST_USE_RESULT MaybeObject* CopyFixedDoubleArrayWithMap(
+      FixedDoubleArray* src, Map* map);
+
   // Allocates a fixed array initialized with the hole values.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
@@ -658,6 +677,11 @@
                                                    Context* previous,
                                                    JSObject* extension);
 
+  // Allocate a block context.
+  MUST_USE_RESULT MaybeObject* AllocateBlockContext(JSFunction* function,
+                                                    Context* previous,
+                                                    SerializedScopeInfo* info);
+
   // Allocates a new utility object in the old generation.
   MUST_USE_RESULT MaybeObject* AllocateStruct(InstanceType type);
 
@@ -1636,6 +1660,7 @@
   friend class Page;
   friend class Isolate;
   friend class MarkCompactCollector;
+  friend class StaticMarkingVisitor;
   friend class MapCompact;
 
   DISALLOW_COPY_AND_ASSIGN(Heap);
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index d282f37..d3cc8a6 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -635,6 +635,13 @@
 }
 
 
+void HBoundsCheck::PrintDataTo(StringStream* stream) {
+  index()->PrintNameTo(stream);
+  stream->Add(" ");
+  length()->PrintNameTo(stream);
+}
+
+
 void HCallConstantFunction::PrintDataTo(StringStream* stream) {
   if (IsApplyFunction()) {
     stream->Add("optimized apply ");
@@ -771,7 +778,7 @@
 void HTypeofIsAndBranch::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
   stream->Add(" == ");
-  stream->Add(type_literal_->ToAsciiVector());
+  stream->Add(type_literal_->GetFlatContent().ToAsciiVector());
 }
 
 
@@ -862,19 +869,25 @@
 
 
 Range* HValue::InferRange() {
-  if (representation().IsTagged()) {
-    // Tagged values are always in int32 range when converted to integer,
-    // but they can contain -0.
-    Range* result = new Range();
-    result->set_can_be_minus_zero(true);
-    return result;
-  } else if (representation().IsNone()) {
-    return NULL;
-  } else {
-    // Untagged integer32 cannot be -0 and we don't compute ranges for
-    // untagged doubles.
-    return new Range();
+  // Untagged integer32 cannot be -0, all other representations can.
+  Range* result = new Range();
+  result->set_can_be_minus_zero(!representation().IsInteger32());
+  return result;
+}
+
+
+Range* HChange::InferRange() {
+  Range* input_range = value()->range();
+  if (from().IsInteger32() &&
+      to().IsTagged() &&
+      input_range != NULL && input_range->IsInSmiRange()) {
+    set_type(HType::Smi());
   }
+  Range* result = (input_range != NULL)
+      ? input_range->Copy()
+      : HValue::InferRange();
+  if (to().IsInteger32()) result->set_can_be_minus_zero(false);
+  return result;
 }
 
 
@@ -1223,6 +1236,7 @@
           ? left()->range()->Copy()
           : new Range();
       result->Sar(c->Integer32Value());
+      result->set_can_be_minus_zero(false);
       return result;
     }
   }
@@ -1230,6 +1244,31 @@
 }
 
 
+Range* HShr::InferRange() {
+  if (right()->IsConstant()) {
+    HConstant* c = HConstant::cast(right());
+    if (c->HasInteger32Value()) {
+      int shift_count = c->Integer32Value() & 0x1f;
+      if (left()->range()->CanBeNegative()) {
+        // Only compute bounds if the result always fits into an int32.
+        return (shift_count >= 1)
+            ? new Range(0, static_cast<uint32_t>(0xffffffff) >> shift_count)
+            : new Range();
+      } else {
+        // For positive inputs we can use the >> operator.
+        Range* result = (left()->range() != NULL)
+            ? left()->range()->Copy()
+            : new Range();
+        result->Sar(c->Integer32Value());
+        result->set_can_be_minus_zero(false);
+        return result;
+      }
+    }
+  }
+  return HValue::InferRange();
+}
+
+
 Range* HShl::InferRange() {
   if (right()->IsConstant()) {
     HConstant* c = HConstant::cast(right());
@@ -1238,6 +1277,7 @@
           ? left()->range()->Copy()
           : new Range();
       result->Shl(c->Integer32Value());
+      result->set_can_be_minus_zero(false);
       return result;
     }
   }
@@ -1285,7 +1325,7 @@
 
 HLoadNamedFieldPolymorphic::HLoadNamedFieldPolymorphic(HValue* context,
                                                        HValue* object,
-                                                       ZoneMapList* types,
+                                                       SmallMapList* types,
                                                        Handle<String> name)
     : types_(Min(types->length(), kMaxLoadPolymorphism)),
       name_(name),
@@ -1349,6 +1389,20 @@
 }
 
 
+void HLoadNamedFieldPolymorphic::PrintDataTo(StringStream* stream) {
+  object()->PrintNameTo(stream);
+  stream->Add(" .");
+  stream->Add(*String::cast(*name())->ToCString());
+}
+
+
+void HLoadNamedGeneric::PrintDataTo(StringStream* stream) {
+  object()->PrintNameTo(stream);
+  stream->Add(" .");
+  stream->Add(*String::cast(*name())->ToCString());
+}
+
+
 void HLoadKeyedFastElement::PrintDataTo(StringStream* stream) {
   object()->PrintNameTo(stream);
   stream->Add("[");
@@ -1798,11 +1852,6 @@
 }
 
 
-void HBoundsCheck::Verify() {
-  HInstruction::Verify();
-}
-
-
 void HCheckSmi::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
@@ -1815,18 +1864,6 @@
 }
 
 
-void HCheckInstanceType::Verify() {
-  HInstruction::Verify();
-  ASSERT(HasNoUses());
-}
-
-
-void HCheckMap::Verify() {
-  HInstruction::Verify();
-  ASSERT(HasNoUses());
-}
-
-
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 15186ff..76007d7 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -104,8 +104,7 @@
   V(Div)                                       \
   V(ElementsKind)                              \
   V(EnterInlined)                              \
-  V(ExternalArrayLength)                       \
-  V(FixedArrayLength)                          \
+  V(FixedArrayBaseLength)                      \
   V(ForceRepresentation)                       \
   V(FunctionLiteral)                           \
   V(GetCachedArrayIndex)                       \
@@ -184,6 +183,7 @@
   V(InobjectFields)                            \
   V(BackingStoreFields)                        \
   V(ArrayElements)                             \
+  V(DoubleArrayElements)                       \
   V(SpecializedArrayElements)                  \
   V(GlobalVars)                                \
   V(Maps)                                      \
@@ -227,14 +227,20 @@
   Range* next() const { return next_; }
   Range* CopyClearLower() const { return new Range(kMinInt, upper_); }
   Range* CopyClearUpper() const { return new Range(lower_, kMaxInt); }
-  Range* Copy() const { return new Range(lower_, upper_); }
+  Range* Copy() const {
+    Range* result = new Range(lower_, upper_);
+    result->set_can_be_minus_zero(CanBeMinusZero());
+    return result;
+  }
   int32_t Mask() const;
   void set_can_be_minus_zero(bool b) { can_be_minus_zero_ = b; }
   bool CanBeMinusZero() const { return CanBeZero() && can_be_minus_zero_; }
   bool CanBeZero() const { return upper_ >= 0 && lower_ <= 0; }
   bool CanBeNegative() const { return lower_ < 0; }
   bool Includes(int value) const { return lower_ <= value && upper_ >= value; }
-  bool IsMostGeneric() const { return lower_ == kMinInt && upper_ == kMaxInt; }
+  bool IsMostGeneric() const {
+    return lower_ == kMinInt && upper_ == kMaxInt && CanBeMinusZero();
+  }
   bool IsInSmiRange() const {
     return lower_ >= Smi::kMinValue && upper_ <= Smi::kMaxValue;
   }
@@ -578,9 +584,9 @@
   virtual bool IsConvertibleToInteger() const { return true; }
 
   HType type() const { return type_; }
-  void set_type(HType type) {
-    ASSERT(HasNoUses());
-    type_ = type;
+  void set_type(HType new_type) {
+    ASSERT(new_type.IsSubtypeOf(type_));
+    type_ = new_type;
   }
 
   // An operation needs to override this function iff:
@@ -933,8 +939,12 @@
 
 class HBranch: public HUnaryControlInstruction {
  public:
-  HBranch(HValue* value, HBasicBlock* true_target, HBasicBlock* false_target)
-      : HUnaryControlInstruction(value, true_target, false_target) {
+  HBranch(HValue* value,
+          HBasicBlock* true_target,
+          HBasicBlock* false_target,
+          ToBooleanStub::Types expected_input_types = ToBooleanStub::no_types())
+      : HUnaryControlInstruction(value, true_target, false_target),
+        expected_input_types_(expected_input_types) {
     ASSERT(true_target != NULL && false_target != NULL);
   }
   explicit HBranch(HValue* value)
@@ -945,7 +955,14 @@
     return Representation::None();
   }
 
+  ToBooleanStub::Types expected_input_types() const {
+    return expected_input_types_;
+  }
+
   DECLARE_CONCRETE_INSTRUCTION(Branch)
+
+ private:
+  ToBooleanStub::Types expected_input_types_;
 };
 
 
@@ -1089,10 +1106,6 @@
     set_representation(to);
     SetFlag(kUseGVN);
     if (is_truncating) SetFlag(kTruncatingToInt32);
-    if (from.IsInteger32() && to.IsTagged() && value->range() != NULL &&
-        value->range()->IsInSmiRange()) {
-      set_type(HType::Smi());
-    }
   }
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
@@ -1104,6 +1117,8 @@
     return from_;
   }
 
+  virtual Range* InferRange();
+
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(Change)
@@ -1663,12 +1678,14 @@
 };
 
 
-class HJSArrayLength: public HUnaryOperation {
+class HJSArrayLength: public HTemplateInstruction<2> {
  public:
-  explicit HJSArrayLength(HValue* value) : HUnaryOperation(value) {
+  HJSArrayLength(HValue* value, HValue* typecheck) {
     // The length of an array is stored as a tagged value in the array
     // object. It is guaranteed to be 32 bit integer, but it can be
     // represented as either a smi or heap number.
+    SetOperandAt(0, value);
+    SetOperandAt(1, typecheck);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnArrayLengths);
@@ -1679,6 +1696,8 @@
     return Representation::Tagged();
   }
 
+  HValue* value() { return OperandAt(0); }
+
   DECLARE_CONCRETE_INSTRUCTION(JSArrayLength)
 
  protected:
@@ -1686,9 +1705,9 @@
 };
 
 
-class HFixedArrayLength: public HUnaryOperation {
+class HFixedArrayBaseLength: public HUnaryOperation {
  public:
-  explicit HFixedArrayLength(HValue* value) : HUnaryOperation(value) {
+  explicit HFixedArrayBaseLength(HValue* value) : HUnaryOperation(value) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnArrayLengths);
@@ -1698,28 +1717,7 @@
     return Representation::Tagged();
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(FixedArrayLength)
-
- protected:
-  virtual bool DataEquals(HValue* other) { return true; }
-};
-
-
-class HExternalArrayLength: public HUnaryOperation {
- public:
-  explicit HExternalArrayLength(HValue* value) : HUnaryOperation(value) {
-    set_representation(Representation::Integer32());
-    // The result of this instruction is idempotent as long as its inputs don't
-    // change.  The length of a pixel array cannot change once set, so it's not
-    // necessary to introduce a kDependsOnArrayLengths or any other dependency.
-    SetFlag(kUseGVN);
-  }
-
-  virtual Representation RequiredInputRepresentation(int index) const {
-    return Representation::Tagged();
-  }
-
-  DECLARE_CONCRETE_INSTRUCTION(ExternalArrayLength)
+  DECLARE_CONCRETE_INSTRUCTION(FixedArrayBaseLength)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
@@ -1894,10 +1892,14 @@
 };
 
 
-class HCheckMap: public HUnaryOperation {
+class HCheckMap: public HTemplateInstruction<2> {
  public:
-  HCheckMap(HValue* value, Handle<Map> map)
-      : HUnaryOperation(value), map_(map) {
+  HCheckMap(HValue* value, Handle<Map> map, HValue* typecheck = NULL)
+      : map_(map) {
+    SetOperandAt(0, value);
+    // If callers don't depend on a typecheck, they can pass in NULL. In that
+    // case we use a copy of the |value| argument as a dummy value.
+    SetOperandAt(1, typecheck != NULL ? typecheck : value);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnMaps);
@@ -1909,10 +1911,7 @@
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
-#ifdef DEBUG
-  virtual void Verify();
-#endif
-
+  HValue* value() { return OperandAt(0); }
   Handle<Map> map() const { return map_; }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMap)
@@ -1980,10 +1979,6 @@
     return Representation::Tagged();
   }
 
-#ifdef DEBUG
-  virtual void Verify();
-#endif
-
   virtual HValue* Canonicalize();
 
   bool is_interval_check() const { return check_ <= LAST_INTERVAL_CHECK; }
@@ -2458,9 +2453,7 @@
     return Representation::Integer32();
   }
 
-#ifdef DEBUG
-  virtual void Verify();
-#endif
+  virtual void PrintDataTo(StringStream* stream);
 
   HValue* index() { return OperandAt(0); }
   HValue* length() { return OperandAt(1); }
@@ -3063,6 +3056,7 @@
   HShr(HValue* context, HValue* left, HValue* right)
       : HBitwiseBinaryOperation(context, left, right) { }
 
+  virtual Range* InferRange();
   virtual HType CalculateInferredType();
 
   DECLARE_CONCRETE_INSTRUCTION(Shr)
@@ -3415,12 +3409,12 @@
  public:
   HLoadNamedFieldPolymorphic(HValue* context,
                              HValue* object,
-                             ZoneMapList* types,
+                             SmallMapList* types,
                              Handle<String> name);
 
   HValue* context() { return OperandAt(0); }
   HValue* object() { return OperandAt(1); }
-  ZoneMapList* types() { return &types_; }
+  SmallMapList* types() { return &types_; }
   Handle<String> name() { return name_; }
   bool need_generic() { return need_generic_; }
 
@@ -3428,6 +3422,8 @@
     return Representation::Tagged();
   }
 
+  virtual void PrintDataTo(StringStream* stream);
+
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedFieldPolymorphic)
 
   static const int kMaxLoadPolymorphism = 4;
@@ -3436,7 +3432,7 @@
   virtual bool DataEquals(HValue* value);
 
  private:
-  ZoneMapList types_;
+  SmallMapList types_;
   Handle<String> name_;
   bool need_generic_;
 };
@@ -3461,6 +3457,8 @@
     return Representation::Tagged();
   }
 
+  virtual void PrintDataTo(StringStream* stream);
+
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedGeneric)
 
  private:
@@ -3527,7 +3525,7 @@
     SetOperandAt(0, elements);
     SetOperandAt(1, key);
     set_representation(Representation::Double());
-    SetFlag(kDependsOnArrayElements);
+    SetFlag(kDependsOnDoubleArrayElements);
     SetFlag(kUseGVN);
   }
 
@@ -3745,7 +3743,7 @@
     SetOperandAt(0, elements);
     SetOperandAt(1, key);
     SetOperandAt(2, val);
-    SetFlag(kChangesArrayElements);
+    SetFlag(kChangesDoubleArrayElements);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index f105703..5772141 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -736,6 +736,8 @@
   HPhase phase("Assign dominators", this);
   for (int i = 0; i < blocks_.length(); ++i) {
     if (blocks_[i]->IsLoopHeader()) {
+      // Only the first predecessor of a loop header is from outside the loop.
+      // All others are back edges, and thus cannot dominate the loop header.
       blocks_[i]->AssignCommonDominator(blocks_[i]->predecessors()->first());
     } else {
       for (int j = 0; j < blocks_[i]->predecessors()->length(); ++j) {
@@ -743,13 +745,15 @@
       }
     }
   }
+}
 
-  // Propagate flag marking blocks containing unconditional deoptimize.
+// Mark all blocks that are dominated by an unconditional soft deoptimize to
+// prevent code motion across those blocks.
+void HGraph::PropagateDeoptimizingMark() {
+  HPhase phase("Propagate deoptimizing mark", this);
   MarkAsDeoptimizingRecursively(entry_block());
 }
 
-
-// Mark all blocks that are dominated by an unconditional deoptimize.
 void HGraph::MarkAsDeoptimizingRecursively(HBasicBlock* block) {
   for (int i = 0; i < block->dominated_blocks()->length(); ++i) {
     HBasicBlock* dominated = block->dominated_blocks()->at(i);
@@ -2182,7 +2186,9 @@
   }
   HBasicBlock* empty_true = builder->graph()->CreateBasicBlock();
   HBasicBlock* empty_false = builder->graph()->CreateBasicBlock();
-  HBranch* test = new(zone()) HBranch(value, empty_true, empty_false);
+  unsigned test_id = condition()->test_id();
+  ToBooleanStub::Types expected(builder->oracle()->ToBooleanTypes(test_id));
+  HBranch* test = new(zone()) HBranch(value, empty_true, empty_false, expected);
   builder->current_block()->Finish(test);
 
   empty_true->Goto(if_true());
@@ -2317,6 +2323,7 @@
 
   graph()->OrderBlocks();
   graph()->AssignDominators();
+  graph()->PropagateDeoptimizingMark();
   if (!graph()->CheckConstPhiUses()) {
     Bailout("Unsupported phi use of const variable");
     return NULL;
@@ -2332,20 +2339,11 @@
   HInferRepresentation rep(graph());
   rep.Analyze();
 
-  if (FLAG_use_range) {
-    HRangeAnalysis rangeAnalysis(graph());
-    rangeAnalysis.Analyze();
-  }
+  graph()->MarkDeoptimizeOnUndefined();
+  graph()->InsertRepresentationChanges();
 
   graph()->InitializeInferredTypes();
   graph()->Canonicalize();
-  graph()->MarkDeoptimizeOnUndefined();
-  graph()->InsertRepresentationChanges();
-  graph()->ComputeMinusZeroChecks();
-
-  // Eliminate redundant stack checks on backwards branches.
-  HStackCheckEliminator sce(graph());
-  sce.Process();
 
   // Perform common subexpression elimination and loop-invariant code motion.
   if (FLAG_use_gvn) {
@@ -2354,6 +2352,16 @@
     gvn.Analyze();
   }
 
+  if (FLAG_use_range) {
+    HRangeAnalysis rangeAnalysis(graph());
+    rangeAnalysis.Analyze();
+  }
+  graph()->ComputeMinusZeroChecks();
+
+  // Eliminate redundant stack checks on backwards branches.
+  HStackCheckEliminator sce(graph());
+  sce.Process();
+
   // Replace the results of check instructions with the original value, if the
   // result is used. This is safe now, since we don't do code motion after this
   // point. It enables better register allocation since the value produced by
@@ -2495,6 +2503,9 @@
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
+  if (stmt->block_scope() != NULL) {
+    return Bailout("ScopedBlock");
+  }
   BreakAndContinueInfo break_info(stmt);
   { BreakAndContinueScope push(&break_info, this);
     CHECK_BAILOUT(VisitStatements(stmt->statements()));
@@ -2646,12 +2657,11 @@
 }
 
 
-void HGraphBuilder::VisitEnterWithContextStatement(
-    EnterWithContextStatement* stmt) {
+void HGraphBuilder::VisitWithStatement(WithStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
-  return Bailout("EnterWithContextStatement");
+  return Bailout("WithStatement");
 }
 
 
@@ -3134,6 +3144,8 @@
   Variable* variable = expr->AsVariable();
   if (variable == NULL) {
     return Bailout("reference to rewritten variable");
+  } else if (variable->mode() == Variable::LET) {
+    return Bailout("reference to let variable");
   } else if (variable->IsStackAllocated()) {
     HValue* value = environment()->Lookup(variable);
     if (variable->mode() == Variable::CONST &&
@@ -3311,8 +3323,8 @@
 
     // Load the elements array before the first store.
     if (elements == NULL)  {
-     elements = new(zone()) HLoadElements(literal);
-     AddInstruction(elements);
+      elements = new(zone()) HLoadElements(literal);
+      AddInstruction(elements);
     }
 
     HValue* key = AddInstruction(
@@ -3408,7 +3420,7 @@
   ASSERT(!name.is_null());
 
   LookupResult lookup;
-  ZoneMapList* types = expr->GetReceiverTypes();
+  SmallMapList* types = expr->GetReceiverTypes();
   bool is_monomorphic = expr->IsMonomorphic() &&
       ComputeStoredField(types->first(), name, &lookup);
 
@@ -3422,7 +3434,7 @@
 void HGraphBuilder::HandlePolymorphicStoreNamedField(Assignment* expr,
                                                      HValue* object,
                                                      HValue* value,
-                                                     ZoneMapList* types,
+                                                     SmallMapList* types,
                                                      Handle<String> name) {
   // TODO(ager): We should recognize when the prototype chains for different
   // maps are identical. In that case we can avoid repeatedly generating the
@@ -3513,7 +3525,7 @@
     Handle<String> name = Handle<String>::cast(key->handle());
     ASSERT(!name.is_null());
 
-    ZoneMapList* types = expr->GetReceiverTypes();
+    SmallMapList* types = expr->GetReceiverTypes();
     LookupResult lookup;
 
     if (expr->IsMonomorphic()) {
@@ -3599,8 +3611,9 @@
   BinaryOperation* operation = expr->binary_operation();
 
   if (var != NULL) {
-    if (var->mode() == Variable::CONST)  {
-      return Bailout("unsupported const compound assignment");
+    if (var->mode() == Variable::CONST ||
+        var->mode() == Variable::LET)  {
+      return Bailout("unsupported let or const compound assignment");
     }
 
     CHECK_ALIVE(VisitForValue(operation));
@@ -3743,6 +3756,8 @@
       // variables (e.g. initialization inside a loop).
       HValue* old_value = environment()->Lookup(var);
       AddInstruction(new HUseConst(old_value));
+    } else if (var->mode() == Variable::LET) {
+      return Bailout("unsupported assignment to let");
     }
 
     if (proxy->IsArguments()) return Bailout("assignment to arguments");
@@ -3945,13 +3960,17 @@
                     : BuildLoadKeyedGeneric(object, key);
   }
   AddInstruction(new(zone()) HCheckNonSmi(object));
-  AddInstruction(new(zone()) HCheckMap(object, map));
-  HInstruction* elements = new(zone()) HLoadElements(object);
+  HInstruction* mapcheck = AddInstruction(new(zone()) HCheckMap(object, map));
+  HInstruction* elements = AddInstruction(new(zone()) HLoadElements(object));
+  bool fast_double_elements = map->has_fast_double_elements();
+  if (is_store && map->has_fast_elements()) {
+    AddInstruction(new(zone()) HCheckMap(
+        elements, isolate()->factory()->fixed_array_map()));
+  }
   HInstruction* length = NULL;
   HInstruction* checked_key = NULL;
   if (map->has_external_array_elements()) {
-    AddInstruction(elements);
-    length = AddInstruction(new(zone()) HExternalArrayLength(elements));
+    length = AddInstruction(new(zone()) HFixedArrayBaseLength(elements));
     checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
     HLoadExternalArrayPointer* external_elements =
         new(zone()) HLoadExternalArrayPointer(elements);
@@ -3959,25 +3978,13 @@
     return BuildExternalArrayElementAccess(external_elements, checked_key,
                                            val, map->elements_kind(), is_store);
   }
-  bool fast_double_elements = map->has_fast_double_elements();
   ASSERT(map->has_fast_elements() || fast_double_elements);
   if (map->instance_type() == JS_ARRAY_TYPE) {
-    length = AddInstruction(new(zone()) HJSArrayLength(object));
-    checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
-    AddInstruction(elements);
-    if (is_store && !fast_double_elements) {
-      AddInstruction(new(zone()) HCheckMap(
-          elements, isolate()->factory()->fixed_array_map()));
-    }
+    length = AddInstruction(new(zone()) HJSArrayLength(object, mapcheck));
   } else {
-    AddInstruction(elements);
-    if (is_store && !fast_double_elements) {
-      AddInstruction(new(zone()) HCheckMap(
-          elements, isolate()->factory()->fixed_array_map()));
-    }
-    length = AddInstruction(new(zone()) HFixedArrayLength(elements));
-    checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
+    length = AddInstruction(new(zone()) HFixedArrayBaseLength(elements));
   }
+  checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
   if (is_store) {
     if (fast_double_elements) {
       return new(zone()) HStoreKeyedFastDoubleElement(elements,
@@ -4007,7 +4014,7 @@
   *has_side_effects = false;
   AddInstruction(new(zone()) HCheckNonSmi(object));
   AddInstruction(HCheckInstanceType::NewIsSpecObject(object));
-  ZoneMapList* maps = prop->GetReceiverTypes();
+  SmallMapList* maps = prop->GetReceiverTypes();
   bool todo_external_array = false;
 
   static const int kNumElementTypes = JSObject::kElementsKindCount;
@@ -4029,7 +4036,8 @@
 
   HInstruction* elements_kind_instr =
       AddInstruction(new(zone()) HElementsKind(object));
-  HInstruction* elements = NULL;
+  HCompareConstantEqAndBranch* elements_kind_branch = NULL;
+  HInstruction* elements = AddInstruction(new(zone()) HLoadElements(object));
   HLoadExternalArrayPointer* external_elements = NULL;
   HInstruction* checked_key = NULL;
 
@@ -4045,16 +4053,8 @@
                   JSObject::LAST_ELEMENTS_KIND);
     if (elements_kind == JSObject::FIRST_EXTERNAL_ARRAY_ELEMENTS_KIND
         && todo_external_array) {
-      elements = AddInstruction(new(zone()) HLoadElements(object));
-      // We need to forcibly prevent some ElementsKind-dependent instructions
-      // from being hoisted out of any loops they might occur in, because
-      // the current loop-invariant-code-motion algorithm isn't clever enough
-      // to deal with them properly.
-      // There's some performance to be gained by developing a smarter
-      // solution for this.
-      elements->ClearFlag(HValue::kUseGVN);
       HInstruction* length =
-          AddInstruction(new(zone()) HExternalArrayLength(elements));
+          AddInstruction(new(zone()) HFixedArrayBaseLength(elements));
       checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
       external_elements = new(zone()) HLoadExternalArrayPointer(elements);
       AddInstruction(external_elements);
@@ -4062,18 +4062,23 @@
     if (type_todo[elements_kind]) {
       HBasicBlock* if_true = graph()->CreateBasicBlock();
       HBasicBlock* if_false = graph()->CreateBasicBlock();
-      HCompareConstantEqAndBranch* compare =
-          new(zone()) HCompareConstantEqAndBranch(elements_kind_instr,
-                                                  elements_kind,
-                                                  Token::EQ_STRICT);
-      compare->SetSuccessorAt(0, if_true);
-      compare->SetSuccessorAt(1, if_false);
-      current_block()->Finish(compare);
+      elements_kind_branch = new(zone()) HCompareConstantEqAndBranch(
+          elements_kind_instr, elements_kind, Token::EQ_STRICT);
+      elements_kind_branch->SetSuccessorAt(0, if_true);
+      elements_kind_branch->SetSuccessorAt(1, if_false);
+      current_block()->Finish(elements_kind_branch);
 
       set_current_block(if_true);
       HInstruction* access;
       if (elements_kind == JSObject::FAST_ELEMENTS ||
           elements_kind == JSObject::FAST_DOUBLE_ELEMENTS) {
+        bool fast_double_elements =
+            elements_kind == JSObject::FAST_DOUBLE_ELEMENTS;
+        if (is_store && elements_kind == JSObject::FAST_ELEMENTS) {
+          AddInstruction(new(zone()) HCheckMap(
+              elements, isolate()->factory()->fixed_array_map(),
+              elements_kind_branch));
+        }
         HBasicBlock* if_jsarray = graph()->CreateBasicBlock();
         HBasicBlock* if_fastobject = graph()->CreateBasicBlock();
         HHasInstanceTypeAndBranch* typecheck =
@@ -4083,14 +4088,9 @@
         current_block()->Finish(typecheck);
 
         set_current_block(if_jsarray);
-        HInstruction* length = new(zone()) HJSArrayLength(object);
+        HInstruction* length = new(zone()) HJSArrayLength(object, typecheck);
         AddInstruction(length);
-        length->ClearFlag(HValue::kUseGVN);
         checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
-        elements = AddInstruction(new(zone()) HLoadElements(object));
-        elements->ClearFlag(HValue::kUseGVN);
-        bool fast_double_elements =
-            elements_kind == JSObject::FAST_DOUBLE_ELEMENTS;
         if (is_store) {
           if (fast_double_elements) {
             access = AddInstruction(
@@ -4098,8 +4098,6 @@
                                                          checked_key,
                                                          val));
           } else {
-            AddInstruction(new(zone()) HCheckMap(
-                elements, isolate()->factory()->fixed_array_map()));
             access = AddInstruction(
                 new(zone()) HStoreKeyedFastElement(elements, checked_key, val));
           }
@@ -4120,13 +4118,7 @@
         if_jsarray->Goto(join);
 
         set_current_block(if_fastobject);
-        elements = AddInstruction(new(zone()) HLoadElements(object));
-        elements->ClearFlag(HValue::kUseGVN);
-        if (is_store && !fast_double_elements) {
-          AddInstruction(new(zone()) HCheckMap(
-              elements, isolate()->factory()->fixed_array_map()));
-        }
-        length = AddInstruction(new(zone()) HFixedArrayLength(elements));
+        length = AddInstruction(new(zone()) HFixedArrayBaseLength(elements));
         checked_key = AddInstruction(new(zone()) HBoundsCheck(key, length));
         if (is_store) {
           if (fast_double_elements) {
@@ -4270,8 +4262,9 @@
   if (expr->IsArrayLength()) {
     HValue* array = Pop();
     AddInstruction(new(zone()) HCheckNonSmi(array));
-    AddInstruction(HCheckInstanceType::NewIsJSArray(array));
-    instr = new(zone()) HJSArrayLength(array);
+    HInstruction* mapcheck =
+        AddInstruction(HCheckInstanceType::NewIsJSArray(array));
+    instr = new(zone()) HJSArrayLength(array, mapcheck);
 
   } else if (expr->IsStringLength()) {
     HValue* string = Pop();
@@ -4295,7 +4288,7 @@
 
   } else if (expr->key()->IsPropertyName()) {
     Handle<String> name = expr->key()->AsLiteral()->AsPropertyName();
-    ZoneMapList* types = expr->GetReceiverTypes();
+    SmallMapList* types = expr->GetReceiverTypes();
 
     HValue* obj = Pop();
     if (expr->IsMonomorphic()) {
@@ -4356,7 +4349,7 @@
 
 void HGraphBuilder::HandlePolymorphicCallNamed(Call* expr,
                                                HValue* receiver,
-                                               ZoneMapList* types,
+                                               SmallMapList* types,
                                                Handle<String> name) {
   // TODO(ager): We should recognize when the prototype chains for different
   // maps are identical. In that case we can avoid repeatedly generating the
@@ -4886,13 +4879,14 @@
 
     Handle<String> name = prop->key()->AsLiteral()->AsPropertyName();
 
-    ZoneMapList* types = expr->GetReceiverTypes();
+    SmallMapList* types = expr->GetReceiverTypes();
 
     HValue* receiver =
         environment()->ExpressionStackAt(expr->arguments()->length());
     if (expr->IsMonomorphic()) {
-      Handle<Map> receiver_map =
-          (types == NULL) ? Handle<Map>::null() : types->first();
+      Handle<Map> receiver_map = (types == NULL || types->is_empty())
+          ? Handle<Map>::null()
+          : types->first();
       if (TryInlineBuiltinFunction(expr,
                                    receiver,
                                    receiver_map,
@@ -5109,19 +5103,13 @@
     // The subexpression does not have side effects.
     return ast_context()->ReturnValue(graph()->GetConstantFalse());
   } else if (prop != NULL) {
-    if (prop->is_synthetic()) {
-      // Result of deleting parameters is false, even when they rewrite
-      // to accesses on the arguments object.
-      return ast_context()->ReturnValue(graph()->GetConstantFalse());
-  } else {
-      CHECK_ALIVE(VisitForValue(prop->obj()));
-      CHECK_ALIVE(VisitForValue(prop->key()));
-      HValue* key = Pop();
-      HValue* obj = Pop();
-      HValue* context = environment()->LookupContext();
-      HDeleteProperty* instr = new(zone()) HDeleteProperty(context, obj, key);
-      return ast_context()->ReturnInstruction(instr, expr->id());
-    }
+    CHECK_ALIVE(VisitForValue(prop->obj()));
+    CHECK_ALIVE(VisitForValue(prop->key()));
+    HValue* key = Pop();
+    HValue* obj = Pop();
+    HValue* context = environment()->LookupContext();
+    HDeleteProperty* instr = new(zone()) HDeleteProperty(context, obj, key);
+    return ast_context()->ReturnInstruction(instr, expr->id());
   } else if (var->is_global()) {
     Bailout("delete with global variable");
   } else {
@@ -5566,9 +5554,11 @@
     // We need an extra block to maintain edge-split form.
     HBasicBlock* empty_block = graph()->CreateBasicBlock();
     HBasicBlock* eval_right = graph()->CreateBasicBlock();
+    unsigned test_id = expr->left()->test_id();
+    ToBooleanStub::Types expected(oracle()->ToBooleanTypes(test_id));
     HBranch* test = is_logical_and
-      ? new(zone()) HBranch(Top(), eval_right, empty_block)
-      : new(zone()) HBranch(Top(), empty_block, eval_right);
+      ? new(zone()) HBranch(Top(), eval_right, empty_block, expected)
+      : new(zone()) HBranch(Top(), empty_block, eval_right, expected);
     current_block()->Finish(test);
 
     set_current_block(eval_right);
@@ -5843,7 +5833,9 @@
 void HGraphBuilder::VisitDeclaration(Declaration* decl) {
   // We support only declarations that do not require code generation.
   Variable* var = decl->proxy()->var();
-  if (!var->IsStackAllocated() || decl->fun() != NULL) {
+  if (!var->IsStackAllocated() ||
+      decl->fun() != NULL ||
+      decl->mode() == Variable::LET) {
     return Bailout("unsupported declaration");
   }
 
@@ -6255,11 +6247,6 @@
 }
 
 
-void HGraphBuilder::GenerateIsNativeOrStrictMode(CallRuntime* call) {
-  return Bailout("inlined runtime function: IsNativeOrStrictMode");
-}
-
-
 #undef CHECK_BAILOUT
 #undef CHECK_ALIVE
 
diff --git a/src/hydrogen.h b/src/hydrogen.h
index ffa8aa7..1066d2c 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -238,7 +238,7 @@
   void OrderBlocks();
   void AssignDominators();
   void ReplaceCheckedValues();
-  void MarkAsDeoptimizingRecursively(HBasicBlock* block);
+  void PropagateDeoptimizingMark();
 
   // Returns false if there are phi-uses of the arguments-object
   // which are not supported by the optimizing compiler.
@@ -299,6 +299,7 @@
   HConstant* GetConstant(SetOncePointer<HConstant>* pointer,
                          Object* value);
 
+  void MarkAsDeoptimizingRecursively(HBasicBlock* block);
   void InsertTypeConversions(HInstruction* instr);
   void PropagateMinusZeroChecks(HValue* value, BitVector* visited);
   void RecursivelyMarkPhiDeoptimizeOnUndefined(HPhi* phi);
@@ -725,6 +726,8 @@
                           HBasicBlock* second,
                           int join_id);
 
+  TypeFeedbackOracle* oracle() const { return function_state()->oracle(); }
+
  private:
   // Type of a member function that generates inline code for a native function.
   typedef void (HGraphBuilder::*InlineFunctionGenerator)(CallRuntime* call);
@@ -753,7 +756,6 @@
   CompilationInfo* info() const {
     return function_state()->compilation_info();
   }
-  TypeFeedbackOracle* oracle() const { return function_state()->oracle(); }
 
   AstContext* call_context() const {
     return function_state()->call_context();
@@ -901,11 +903,11 @@
   void HandlePolymorphicStoreNamedField(Assignment* expr,
                                         HValue* object,
                                         HValue* value,
-                                        ZoneMapList* types,
+                                        SmallMapList* types,
                                         Handle<String> name);
   void HandlePolymorphicCallNamed(Call* expr,
                                   HValue* receiver,
-                                  ZoneMapList* types,
+                                  SmallMapList* types,
                                   Handle<String> name);
   void HandleLiteralCompareTypeof(CompareOperation* compare_expr,
                                   Expression* expr,
diff --git a/src/ia32/assembler-ia32.cc b/src/ia32/assembler-ia32.cc
index 0dc5194..9996474 100644
--- a/src/ia32/assembler-ia32.cc
+++ b/src/ia32/assembler-ia32.cc
@@ -1957,6 +1957,18 @@
 }
 
 
+void Assembler::roundsd(XMMRegister dst, XMMRegister src, RoundingMode mode) {
+  ASSERT(CpuFeatures::IsEnabled(SSE4_1));
+  EnsureSpace ensure_space(this);
+  EMIT(0x66);
+  EMIT(0x0F);
+  EMIT(0x3A);
+  EMIT(0x0B);
+  emit_sse_operand(dst, src);
+  // Mask precision exeption.
+  EMIT(static_cast<byte>(mode) | 0x8);
+}
+
 void Assembler::movmskpd(Register dst, XMMRegister src) {
   ASSERT(CpuFeatures::IsEnabled(SSE2));
   EnsureSpace ensure_space(this);
diff --git a/src/ia32/assembler-ia32.h b/src/ia32/assembler-ia32.h
index da38e13..c186094 100644
--- a/src/ia32/assembler-ia32.h
+++ b/src/ia32/assembler-ia32.h
@@ -941,6 +941,16 @@
   void andpd(XMMRegister dst, XMMRegister src);
 
   void ucomisd(XMMRegister dst, XMMRegister src);
+
+  enum RoundingMode {
+    kRoundToNearest = 0x0,
+    kRoundDown      = 0x1,
+    kRoundUp        = 0x2,
+    kRoundToZero    = 0x3
+  };
+
+  void roundsd(XMMRegister dst, XMMRegister src, RoundingMode mode);
+
   void movmskpd(Register dst, XMMRegister src);
 
   void cmpltsd(XMMRegister dst, XMMRegister src);
diff --git a/src/ia32/builtins-ia32.cc b/src/ia32/builtins-ia32.cc
index f8a85de..845a073 100644
--- a/src/ia32/builtins-ia32.cc
+++ b/src/ia32/builtins-ia32.cc
@@ -373,7 +373,7 @@
   __ LeaveConstructFrame();
 
   // Remove caller arguments from the stack and return.
-  ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
   __ pop(ecx);
   __ lea(esp, Operand(esp, ebx, times_2, 1 * kPointerSize));  // 1 ~ receiver
   __ push(ecx);
@@ -923,7 +923,7 @@
   // Fill the FixedArray with the hole value. Inline the code if short.
   // Reconsider loop unfolding if kPreallocatedArrayElements gets changed.
   static const int kLoopUnfoldLimit = 4;
-  ASSERT(kPreallocatedArrayElements <= kLoopUnfoldLimit);
+  STATIC_ASSERT(kPreallocatedArrayElements <= kLoopUnfoldLimit);
   if (initial_capacity <= kLoopUnfoldLimit) {
     // Use a scratch register here to have only one reloc info when unfolding
     // the loop.
@@ -975,7 +975,7 @@
 
   // Allocate the JSArray object together with space for a FixedArray with the
   // requested elements.
-  ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
   __ AllocateInNewSpace(JSArray::kSize + FixedArray::kHeaderSize,
                         times_half_pointer_size,  // array_size is a smi.
                         array_size,
@@ -1100,7 +1100,7 @@
   __ bind(&argc_one_or_more);
   __ cmp(eax, 1);
   __ j(not_equal, &argc_two_or_more);
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ mov(ecx, Operand(esp, (push_count + 1) * kPointerSize));
   __ test(ecx, Operand(ecx));
   __ j(not_zero, &not_empty_array);
@@ -1155,7 +1155,7 @@
 
   // Handle construction of an array from a list of arguments.
   __ bind(&argc_two_or_more);
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ SmiTag(eax);  // Convet argc to a smi.
   // eax: array_size (smi)
   // edi: constructor
@@ -1437,7 +1437,7 @@
   // Preserve the number of arguments on the stack. Must preserve eax,
   // ebx and ecx because these registers are used when copying the
   // arguments and the receiver.
-  ASSERT(kSmiTagSize == 1);
+  STATIC_ASSERT(kSmiTagSize == 1);
   __ lea(edi, Operand(eax, eax, times_1, kSmiTag));
   __ push(edi);
 }
@@ -1451,7 +1451,7 @@
   __ leave();
 
   // Remove caller arguments from the stack.
-  ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
   __ pop(ecx);
   __ lea(esp, Operand(esp, ebx, times_2, 1 * kPointerSize));  // 1 ~ receiver
   __ push(ecx);
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 71aacf9..85e74b8 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -236,69 +236,141 @@
 }
 
 
-// The stub returns zero for false, and a non-zero value for true.
+// The stub expects its argument on the stack and returns its result in tos_:
+// zero for false, and a non-zero value for true.
 void ToBooleanStub::Generate(MacroAssembler* masm) {
-  Label false_result, true_result, not_string;
+  Label patch;
   Factory* factory = masm->isolate()->factory();
+  const Register argument = eax;
   const Register map = edx;
 
-  __ mov(eax, Operand(esp, 1 * kPointerSize));
+  if (!types_.IsEmpty()) {
+    __ mov(argument, Operand(esp, 1 * kPointerSize));
+  }
 
   // undefined -> false
-  __ cmp(eax, factory->undefined_value());
-  __ j(equal, &false_result);
+  CheckOddball(masm, UNDEFINED, Heap::kUndefinedValueRootIndex, false);
 
   // Boolean -> its value
-  __ cmp(eax, factory->false_value());
-  __ j(equal, &false_result);
-  __ cmp(eax, factory->true_value());
-  __ j(equal, &true_result);
-
-  // Smis: 0 -> false, all other -> true
-  __ test(eax, Operand(eax));
-  __ j(zero, &false_result);
-  __ JumpIfSmi(eax, &true_result);
+  CheckOddball(masm, BOOLEAN, Heap::kFalseValueRootIndex, false);
+  CheckOddball(masm, BOOLEAN, Heap::kTrueValueRootIndex, true);
 
   // 'null' -> false.
-  __ cmp(eax, factory->null_value());
-  __ j(equal, &false_result, Label::kNear);
+  CheckOddball(masm, NULL_TYPE, Heap::kNullValueRootIndex, false);
 
-  // Get the map of the heap object.
-  __ mov(map, FieldOperand(eax, HeapObject::kMapOffset));
+  if (types_.Contains(SMI)) {
+    // Smis: 0 -> false, all other -> true
+    Label not_smi;
+    __ JumpIfNotSmi(argument, &not_smi, Label::kNear);
+    // argument contains the correct return value already.
+    if (!tos_.is(argument)) {
+      __ mov(tos_, argument);
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&not_smi);
+  } else if (types_.NeedsMap()) {
+    // If we need a map later and have a Smi -> patch.
+    __ JumpIfSmi(argument, &patch, Label::kNear);
+  }
 
-  // Undetectable -> false.
-  __ test_b(FieldOperand(map, Map::kBitFieldOffset),
-            1 << Map::kIsUndetectable);
-  __ j(not_zero, &false_result, Label::kNear);
+  if (types_.NeedsMap()) {
+    __ mov(map, FieldOperand(argument, HeapObject::kMapOffset));
 
-  // JavaScript object -> true.
-  __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
-  __ j(above_equal, &true_result, Label::kNear);
+    if (types_.CanBeUndetectable()) {
+      __ test_b(FieldOperand(map, Map::kBitFieldOffset),
+                1 << Map::kIsUndetectable);
+      // Undetectable -> false.
+      Label not_undetectable;
+      __ j(zero, &not_undetectable, Label::kNear);
+      __ Set(tos_, Immediate(0));
+      __ ret(1 * kPointerSize);
+      __ bind(&not_undetectable);
+    }
+  }
 
-  // String value -> false iff empty.
-  __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
-  __ j(above_equal, &not_string, Label::kNear);
-  __ cmp(FieldOperand(eax, String::kLengthOffset), Immediate(0));
-  __ j(zero, &false_result, Label::kNear);
-  __ jmp(&true_result, Label::kNear);
+  if (types_.Contains(SPEC_OBJECT)) {
+    // spec object -> true.
+    Label not_js_object;
+    __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
+    __ j(below, &not_js_object, Label::kNear);
+    // argument contains the correct return value already.
+    if (!tos_.is(argument)) {
+      __ Set(tos_, Immediate(1));
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&not_js_object);
+  }
 
-  __ bind(&not_string);
-  // HeapNumber -> false iff +0, -0, or NaN.
-  __ cmp(map, factory->heap_number_map());
-  __ j(not_equal, &true_result, Label::kNear);
-  __ fldz();
-  __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
-  __ FCmp();
-  __ j(zero, &false_result, Label::kNear);
-  // Fall through to |true_result|.
+  if (types_.Contains(STRING)) {
+    // String value -> false iff empty.
+    Label not_string;
+    __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
+    __ j(above_equal, &not_string, Label::kNear);
+    __ mov(tos_, FieldOperand(argument, String::kLengthOffset));
+    __ ret(1 * kPointerSize);  // the string length is OK as the return value
+    __ bind(&not_string);
+  }
 
-  // Return 1/0 for true/false in tos_.
-  __ bind(&true_result);
-  __ mov(tos_, 1);
-  __ ret(1 * kPointerSize);
-  __ bind(&false_result);
-  __ mov(tos_, 0);
-  __ ret(1 * kPointerSize);
+  if (types_.Contains(HEAP_NUMBER)) {
+    // heap number -> false iff +0, -0, or NaN.
+    Label not_heap_number, false_result;
+    __ cmp(map, factory->heap_number_map());
+    __ j(not_equal, &not_heap_number, Label::kNear);
+    __ fldz();
+    __ fld_d(FieldOperand(argument, HeapNumber::kValueOffset));
+    __ FCmp();
+    __ j(zero, &false_result, Label::kNear);
+    // argument contains the correct return value already.
+    if (!tos_.is(argument)) {
+      __ Set(tos_, Immediate(1));
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&false_result);
+    __ Set(tos_, Immediate(0));
+    __ ret(1 * kPointerSize);
+    __ bind(&not_heap_number);
+  }
+
+  __ bind(&patch);
+  GenerateTypeTransition(masm);
+}
+
+
+void ToBooleanStub::CheckOddball(MacroAssembler* masm,
+                                 Type type,
+                                 Heap::RootListIndex value,
+                                 bool result) {
+  const Register argument = eax;
+  if (types_.Contains(type)) {
+    // If we see an expected oddball, return its ToBoolean value tos_.
+    Label different_value;
+    __ CompareRoot(argument, value);
+    __ j(not_equal, &different_value, Label::kNear);
+    if (!result) {
+      // If we have to return zero, there is no way around clearing tos_.
+      __ Set(tos_, Immediate(0));
+    } else if (!tos_.is(argument)) {
+      // If we have to return non-zero, we can re-use the argument if it is the
+      // same register as the result, because we never see Smi-zero here.
+      __ Set(tos_, Immediate(1));
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&different_value);
+  }
+}
+
+
+void ToBooleanStub::GenerateTypeTransition(MacroAssembler* masm) {
+  __ pop(ecx);  // Get return address, operand is now on top of stack.
+  __ push(Immediate(Smi::FromInt(tos_.code())));
+  __ push(Immediate(Smi::FromInt(types_.ToByte())));
+  __ push(ecx);  // Push return address.
+  // Patch the caller to an appropriate specialized stub and return the
+  // operation result to the caller of the stub.
+  __ TailCallExternalReference(
+      ExternalReference(IC_Utility(IC::kToBoolean_Patch), masm->isolate()),
+      3,
+      1);
 }
 
 
@@ -421,10 +493,10 @@
     __ cmp(Operand(scratch2), Immediate(non_smi_exponent));
     // If we have a match of the int32-but-not-Smi exponent then skip some
     // logic.
-    __ j(equal, &right_exponent);
+    __ j(equal, &right_exponent, Label::kNear);
     // If the exponent is higher than that then go to slow case.  This catches
     // numbers that don't fit in a signed int32, infinities and NaNs.
-    __ j(less, &normal_exponent);
+    __ j(less, &normal_exponent, Label::kNear);
 
     {
       // Handle a big exponent.  The only reason we have this code is that the
@@ -453,9 +525,9 @@
       __ or_(ecx, Operand(scratch2));
       // We have the answer in ecx, but we may need to negate it.
       __ test(scratch, Operand(scratch));
-      __ j(positive, &done);
+      __ j(positive, &done, Label::kNear);
       __ neg(ecx);
-      __ jmp(&done);
+      __ jmp(&done, Label::kNear);
     }
 
     __ bind(&normal_exponent);
@@ -468,7 +540,7 @@
         (HeapNumber::kExponentBias + 0) << HeapNumber::kExponentShift;
     __ sub(Operand(scratch2), Immediate(zero_exponent));
     // ecx already has a Smi zero.
-    __ j(less, &done);
+    __ j(less, &done, Label::kNear);
 
     // We have a shifted exponent between 0 and 30 in scratch2.
     __ shr(scratch2, HeapNumber::kExponentShift);
@@ -693,7 +765,7 @@
 
     Label slow_allocate_heapnumber, heapnumber_allocated;
     __ AllocateHeapNumber(eax, ebx, ecx, &slow_allocate_heapnumber);
-    __ jmp(&heapnumber_allocated);
+    __ jmp(&heapnumber_allocated, Label::kNear);
 
     __ bind(&slow_allocate_heapnumber);
     __ EnterInternalFrame();
@@ -1370,14 +1442,14 @@
   Register right = eax;
 
   // Test if left operand is a string.
-  __ JumpIfSmi(left, &call_runtime);
+  __ JumpIfSmi(left, &call_runtime, Label::kNear);
   __ CmpObjectType(left, FIRST_NONSTRING_TYPE, ecx);
-  __ j(above_equal, &call_runtime);
+  __ j(above_equal, &call_runtime, Label::kNear);
 
   // Test if right operand is a string.
-  __ JumpIfSmi(right, &call_runtime);
+  __ JumpIfSmi(right, &call_runtime, Label::kNear);
   __ CmpObjectType(right, FIRST_NONSTRING_TYPE, ecx);
-  __ j(above_equal, &call_runtime);
+  __ j(above_equal, &call_runtime, Label::kNear);
 
   StringAddStub string_add_stub(NO_STRING_CHECK_IN_STUB);
   GenerateRegisterArgsPush(masm);
@@ -1491,7 +1563,7 @@
       } else {
         // Check if result fits in a smi.
         __ cmp(eax, 0xc0000000);
-        __ j(negative, &non_smi_result);
+        __ j(negative, &non_smi_result, Label::kNear);
       }
       // Tag smi result and return.
       __ SmiTag(eax);
@@ -1705,7 +1777,7 @@
       } else {
         // Check if result fits in a smi.
         __ cmp(eax, 0xc0000000);
-        __ j(negative, &non_smi_result);
+        __ j(negative, &non_smi_result, Label::kNear);
       }
       // Tag smi result and return.
       __ SmiTag(eax);
@@ -1904,7 +1976,7 @@
       } else {
         // Check if result fits in a smi.
         __ cmp(eax, 0xc0000000);
-        __ j(negative, &non_smi_result);
+        __ j(negative, &non_smi_result, Label::kNear);
       }
       // Tag smi result and return.
       __ SmiTag(eax);
@@ -2379,7 +2451,7 @@
   Label load_arg2, done;
 
   // Test if arg1 is a Smi.
-  __ JumpIfNotSmi(edx, &arg1_is_object);
+  __ JumpIfNotSmi(edx, &arg1_is_object, Label::kNear);
 
   __ SmiUntag(edx);
   __ jmp(&load_arg2);
@@ -2405,7 +2477,7 @@
   __ bind(&load_arg2);
 
   // Test if arg2 is a Smi.
-  __ JumpIfNotSmi(eax, &arg2_is_object);
+  __ JumpIfNotSmi(eax, &arg2_is_object, Label::kNear);
 
   __ SmiUntag(eax);
   __ mov(ecx, eax);
@@ -2795,7 +2867,7 @@
 
   // Check that the key is a smi.
   Label slow;
-  __ JumpIfNotSmi(edx, &slow);
+  __ JumpIfNotSmi(edx, &slow, Label::kNear);
 
   // Check if the calling frame is an arguments adaptor frame.
   Label adaptor;
@@ -2808,7 +2880,7 @@
   // through register eax. Use unsigned comparison to get negative
   // check for free.
   __ cmp(edx, Operand(eax));
-  __ j(above_equal, &slow);
+  __ j(above_equal, &slow, Label::kNear);
 
   // Read the argument from the stack and return it.
   STATIC_ASSERT(kSmiTagSize == 1);
@@ -2824,7 +2896,7 @@
   __ bind(&adaptor);
   __ mov(ecx, Operand(ebx, ArgumentsAdaptorFrameConstants::kLengthOffset));
   __ cmp(edx, Operand(ecx));
-  __ j(above_equal, &slow);
+  __ j(above_equal, &slow, Label::kNear);
 
   // Read the argument from the stack and return it.
   STATIC_ASSERT(kSmiTagSize == 1);
@@ -3103,11 +3175,11 @@
   __ mov(edx, Operand(ebp, StandardFrameConstants::kCallerFPOffset));
   __ mov(ecx, Operand(edx, StandardFrameConstants::kContextOffset));
   __ cmp(Operand(ecx), Immediate(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
-  __ j(equal, &adaptor_frame);
+  __ j(equal, &adaptor_frame, Label::kNear);
 
   // Get the length from the frame.
   __ mov(ecx, Operand(esp, 1 * kPointerSize));
-  __ jmp(&try_allocate);
+  __ jmp(&try_allocate, Label::kNear);
 
   // Patch the arguments.length and the parameters pointer.
   __ bind(&adaptor_frame);
@@ -3153,7 +3225,7 @@
   // If there are no actual arguments, we're done.
   Label done;
   __ test(ecx, Operand(ecx));
-  __ j(zero, &done);
+  __ j(zero, &done, Label::kNear);
 
   // Get the parameters pointer from the stack.
   __ mov(edx, Operand(esp, 2 * kPointerSize));
@@ -3299,6 +3371,8 @@
   __ cmp(edx, Operand(eax));
   __ j(greater, &runtime);
 
+  // Reset offset for possibly sliced string.
+  __ Set(edi, Immediate(0));
   // ecx: RegExp data (FixedArray)
   // Check the representation and encoding of the subject string.
   Label seq_ascii_string, seq_two_byte_string, check_code;
@@ -3309,36 +3383,45 @@
   __ and_(ebx,
           kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask);
   STATIC_ASSERT((kStringTag | kSeqStringTag | kTwoByteStringTag) == 0);
-  __ j(zero, &seq_two_byte_string);
+  __ j(zero, &seq_two_byte_string, Label::kNear);
   // Any other flat string must be a flat ascii string.
-  __ test(Operand(ebx),
+  __ and_(Operand(ebx),
           Immediate(kIsNotStringMask | kStringRepresentationMask));
-  __ j(zero, &seq_ascii_string);
+  __ j(zero, &seq_ascii_string, Label::kNear);
 
-  // Check for flat cons string.
+  // Check for flat cons string or sliced string.
   // A flat cons string is a cons string where the second part is the empty
   // string. In that case the subject string is just the first part of the cons
   // string. Also in this case the first part of the cons string is known to be
   // a sequential string or an external string.
-  STATIC_ASSERT(kExternalStringTag != 0);
-  STATIC_ASSERT((kConsStringTag & kExternalStringTag) == 0);
-  __ test(Operand(ebx),
-          Immediate(kIsNotStringMask | kExternalStringTag));
-  __ j(not_zero, &runtime);
-  // String is a cons string.
-  __ mov(edx, FieldOperand(eax, ConsString::kSecondOffset));
-  __ cmp(Operand(edx), factory->empty_string());
+  // In the case of a sliced string its offset has to be taken into account.
+  Label cons_string, check_encoding;
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ cmp(Operand(ebx), Immediate(kExternalStringTag));
+  __ j(less, &cons_string);
+  __ j(equal, &runtime);
+
+  // String is sliced.
+  __ mov(edi, FieldOperand(eax, SlicedString::kOffsetOffset));
+  __ mov(eax, FieldOperand(eax, SlicedString::kParentOffset));
+  // edi: offset of sliced string, smi-tagged.
+  // eax: parent string.
+  __ jmp(&check_encoding, Label::kNear);
+  // String is a cons string, check whether it is flat.
+  __ bind(&cons_string);
+  __ cmp(FieldOperand(eax, ConsString::kSecondOffset), factory->empty_string());
   __ j(not_equal, &runtime);
   __ mov(eax, FieldOperand(eax, ConsString::kFirstOffset));
+  __ bind(&check_encoding);
   __ mov(ebx, FieldOperand(eax, HeapObject::kMapOffset));
-  // String is a cons string with empty second part.
-  // eax: first part of cons string.
-  // ebx: map of first part of cons string.
-  // Is first part a flat two byte string?
+  // eax: first part of cons string or parent of sliced string.
+  // ebx: map of first part of cons string or map of parent of sliced string.
+  // Is first part of cons or parent of slice a flat two byte string?
   __ test_b(FieldOperand(ebx, Map::kInstanceTypeOffset),
             kStringRepresentationMask | kStringEncodingMask);
   STATIC_ASSERT((kSeqStringTag | kTwoByteStringTag) == 0);
-  __ j(zero, &seq_two_byte_string);
+  __ j(zero, &seq_two_byte_string, Label::kNear);
   // Any other flat string must be ascii.
   __ test_b(FieldOperand(ebx, Map::kInstanceTypeOffset),
             kStringRepresentationMask);
@@ -3348,14 +3431,14 @@
   // eax: subject string (flat ascii)
   // ecx: RegExp data (FixedArray)
   __ mov(edx, FieldOperand(ecx, JSRegExp::kDataAsciiCodeOffset));
-  __ Set(edi, Immediate(1));  // Type is ascii.
-  __ jmp(&check_code);
+  __ Set(ecx, Immediate(1));  // Type is ascii.
+  __ jmp(&check_code, Label::kNear);
 
   __ bind(&seq_two_byte_string);
   // eax: subject string (flat two byte)
   // ecx: RegExp data (FixedArray)
   __ mov(edx, FieldOperand(ecx, JSRegExp::kDataUC16CodeOffset));
-  __ Set(edi, Immediate(0));  // Type is two byte.
+  __ Set(ecx, Immediate(0));  // Type is two byte.
 
   __ bind(&check_code);
   // Check that the irregexp code has been generated for the actual string
@@ -3365,7 +3448,7 @@
 
   // eax: subject string
   // edx: code
-  // edi: encoding of subject string (1 if ascii, 0 if two_byte);
+  // ecx: encoding of subject string (1 if ascii, 0 if two_byte);
   // Load used arguments before starting to push arguments for call to native
   // RegExp code to avoid handling changing stack height.
   __ mov(ebx, Operand(esp, kPreviousIndexOffset));
@@ -3374,7 +3457,7 @@
   // eax: subject string
   // ebx: previous index
   // edx: code
-  // edi: encoding of subject string (1 if ascii 0 if two_byte);
+  // ecx: encoding of subject string (1 if ascii 0 if two_byte);
   // All checks done. Now push arguments for native regexp code.
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->regexp_entry_native(), 1);
@@ -3391,23 +3474,47 @@
   __ mov(Operand(esp, 6 * kPointerSize), Immediate(1));
 
   // Argument 6: Start (high end) of backtracking stack memory area.
-  __ mov(ecx, Operand::StaticVariable(address_of_regexp_stack_memory_address));
-  __ add(ecx, Operand::StaticVariable(address_of_regexp_stack_memory_size));
-  __ mov(Operand(esp, 5 * kPointerSize), ecx);
+  __ mov(esi, Operand::StaticVariable(address_of_regexp_stack_memory_address));
+  __ add(esi, Operand::StaticVariable(address_of_regexp_stack_memory_size));
+  __ mov(Operand(esp, 5 * kPointerSize), esi);
 
   // Argument 5: static offsets vector buffer.
   __ mov(Operand(esp, 4 * kPointerSize),
          Immediate(ExternalReference::address_of_static_offsets_vector(
              masm->isolate())));
 
+  // Argument 2: Previous index.
+  __ mov(Operand(esp, 1 * kPointerSize), ebx);
+
+  // Argument 1: Original subject string.
+  // The original subject is in the previous stack frame. Therefore we have to
+  // use ebp, which points exactly to one pointer size below the previous esp.
+  // (Because creating a new stack frame pushes the previous ebp onto the stack
+  // and thereby moves up esp by one kPointerSize.)
+  __ mov(esi, Operand(ebp, kSubjectOffset + kPointerSize));
+  __ mov(Operand(esp, 0 * kPointerSize), esi);
+
+  // esi: original subject string
+  // eax: underlying subject string
+  // ebx: previous index
+  // ecx: encoding of subject string (1 if ascii 0 if two_byte);
+  // edx: code
   // Argument 4: End of string data
   // Argument 3: Start of string data
-  Label setup_two_byte, setup_rest;
-  __ test(edi, Operand(edi));
-  __ mov(edi, FieldOperand(eax, String::kLengthOffset));
-  __ j(zero, &setup_two_byte, Label::kNear);
+  // Prepare start and end index of the input.
+  // Load the length from the original sliced string if that is the case.
+  __ mov(esi, FieldOperand(esi, String::kLengthOffset));
+  __ add(esi, Operand(edi));  // Calculate input end wrt offset.
   __ SmiUntag(edi);
-  __ lea(ecx, FieldOperand(eax, edi, times_1, SeqAsciiString::kHeaderSize));
+  __ add(ebx, Operand(edi));  // Calculate input start wrt offset.
+
+  // ebx: start index of the input string
+  // esi: end index of the input string
+  Label setup_two_byte, setup_rest;
+  __ test(ecx, Operand(ecx));
+  __ j(zero, &setup_two_byte, Label::kNear);
+  __ SmiUntag(esi);
+  __ lea(ecx, FieldOperand(eax, esi, times_1, SeqAsciiString::kHeaderSize));
   __ mov(Operand(esp, 3 * kPointerSize), ecx);  // Argument 4.
   __ lea(ecx, FieldOperand(eax, ebx, times_1, SeqAsciiString::kHeaderSize));
   __ mov(Operand(esp, 2 * kPointerSize), ecx);  // Argument 3.
@@ -3415,20 +3522,14 @@
 
   __ bind(&setup_two_byte);
   STATIC_ASSERT(kSmiTag == 0);
-  STATIC_ASSERT(kSmiTagSize == 1);  // edi is smi (powered by 2).
-  __ lea(ecx, FieldOperand(eax, edi, times_1, SeqTwoByteString::kHeaderSize));
+  STATIC_ASSERT(kSmiTagSize == 1);  // esi is smi (powered by 2).
+  __ lea(ecx, FieldOperand(eax, esi, times_1, SeqTwoByteString::kHeaderSize));
   __ mov(Operand(esp, 3 * kPointerSize), ecx);  // Argument 4.
   __ lea(ecx, FieldOperand(eax, ebx, times_2, SeqTwoByteString::kHeaderSize));
   __ mov(Operand(esp, 2 * kPointerSize), ecx);  // Argument 3.
 
   __ bind(&setup_rest);
 
-  // Argument 2: Previous index.
-  __ mov(Operand(esp, 1 * kPointerSize), ebx);
-
-  // Argument 1: Subject string.
-  __ mov(Operand(esp, 0 * kPointerSize), eax);
-
   // Locate the code entry and call it.
   __ add(Operand(edx), Immediate(Code::kHeaderSize - kHeapObjectTag));
   __ call(Operand(edx));
@@ -3467,7 +3568,7 @@
   // by javascript code.
   __ cmp(eax, factory->termination_exception());
   Label throw_termination_exception;
-  __ j(equal, &throw_termination_exception);
+  __ j(equal, &throw_termination_exception, Label::kNear);
 
   // Handle normal exception by following handler chain.
   __ Throw(eax);
@@ -3750,16 +3851,16 @@
 void CompareStub::Generate(MacroAssembler* masm) {
   ASSERT(lhs_.is(no_reg) && rhs_.is(no_reg));
 
-  Label check_unequal_objects, done;
+  Label check_unequal_objects;
 
   // Compare two smis if required.
   if (include_smi_compare_) {
     Label non_smi, smi_done;
     __ mov(ecx, Operand(edx));
     __ or_(ecx, Operand(eax));
-    __ JumpIfNotSmi(ecx, &non_smi);
+    __ JumpIfNotSmi(ecx, &non_smi, Label::kNear);
     __ sub(edx, Operand(eax));  // Return on the result of the subtraction.
-    __ j(no_overflow, &smi_done);
+    __ j(no_overflow, &smi_done, Label::kNear);
     __ not_(edx);  // Correct sign in case of overflow. edx is never 0 here.
     __ bind(&smi_done);
     __ mov(eax, edx);
@@ -3881,7 +3982,7 @@
     __ cmp(FieldOperand(ebx, HeapObject::kMapOffset),
            Immediate(masm->isolate()->factory()->heap_number_map()));
     // If heap number, handle it in the slow case.
-    __ j(equal, &slow);
+    __ j(equal, &slow, Label::kNear);
     // Return non-equal (ebx is not zero)
     __ mov(eax, ebx);
     __ ret(0);
@@ -3932,7 +4033,7 @@
       __ ucomisd(xmm0, xmm1);
 
       // Don't base result on EFLAGS when a NaN is involved.
-      __ j(parity_even, &unordered);
+      __ j(parity_even, &unordered, Label::kNear);
       // Return a result of -1, 0, or 1, based on EFLAGS.
       __ mov(eax, 0);  // equal
       __ mov(ecx, Immediate(Smi::FromInt(1)));
@@ -3948,12 +4049,12 @@
       __ FCmp();
 
       // Don't base result on EFLAGS when a NaN is involved.
-      __ j(parity_even, &unordered);
+      __ j(parity_even, &unordered, Label::kNear);
 
       Label below_label, above_label;
       // Return a result of -1, 0, or 1, based on EFLAGS.
-      __ j(below, &below_label);
-      __ j(above, &above_label);
+      __ j(below, &below_label, Label::kNear);
+      __ j(above, &above_label, Label::kNear);
 
       __ Set(eax, Immediate(0));
       __ ret(0);
@@ -4268,7 +4369,7 @@
   // If the returned exception is RETRY_AFTER_GC continue at retry label
   STATIC_ASSERT(Failure::RETRY_AFTER_GC == 0);
   __ test(eax, Immediate(((1 << kFailureTypeTagSize) - 1) << kFailureTagSize));
-  __ j(zero, &retry);
+  __ j(zero, &retry, Label::kNear);
 
   // Special handling of out of memory exceptions.
   __ cmp(eax, reinterpret_cast<int32_t>(Failure::OutOfMemoryException()));
@@ -4388,11 +4489,11 @@
   ExternalReference js_entry_sp(Isolate::k_js_entry_sp_address,
                                 masm->isolate());
   __ cmp(Operand::StaticVariable(js_entry_sp), Immediate(0));
-  __ j(not_equal, &not_outermost_js);
+  __ j(not_equal, &not_outermost_js, Label::kNear);
   __ mov(Operand::StaticVariable(js_entry_sp), ebp);
   __ push(Immediate(Smi::FromInt(StackFrame::OUTERMOST_JSENTRY_FRAME)));
   Label cont;
-  __ jmp(&cont);
+  __ jmp(&cont, Label::kNear);
   __ bind(&not_outermost_js);
   __ push(Immediate(Smi::FromInt(StackFrame::INNER_JSENTRY_FRAME)));
   __ bind(&cont);
@@ -4633,26 +4734,26 @@
   __ bind(&not_js_object);
   // Before null, smi and string value checks, check that the rhs is a function
   // as for a non-function rhs an exception needs to be thrown.
-  __ JumpIfSmi(function, &slow);
+  __ JumpIfSmi(function, &slow, Label::kNear);
   __ CmpObjectType(function, JS_FUNCTION_TYPE, scratch);
-  __ j(not_equal, &slow);
+  __ j(not_equal, &slow, Label::kNear);
 
   // Null is not instance of anything.
   __ cmp(object, factory->null_value());
-  __ j(not_equal, &object_not_null);
+  __ j(not_equal, &object_not_null, Label::kNear);
   __ Set(eax, Immediate(Smi::FromInt(1)));
   __ ret((HasArgsInRegisters() ? 0 : 2) * kPointerSize);
 
   __ bind(&object_not_null);
   // Smi values is not instance of anything.
-  __ JumpIfNotSmi(object, &object_not_null_or_smi);
+  __ JumpIfNotSmi(object, &object_not_null_or_smi, Label::kNear);
   __ Set(eax, Immediate(Smi::FromInt(1)));
   __ ret((HasArgsInRegisters() ? 0 : 2) * kPointerSize);
 
   __ bind(&object_not_null_or_smi);
   // String values is not instance of anything.
   Condition is_string = masm->IsObjectStringType(object, scratch, scratch);
-  __ j(NegateCondition(is_string), &slow);
+  __ j(NegateCondition(is_string), &slow, Label::kNear);
   __ Set(eax, Immediate(Smi::FromInt(1)));
   __ ret((HasArgsInRegisters() ? 0 : 2) * kPointerSize);
 
@@ -4739,6 +4840,7 @@
   Label flat_string;
   Label ascii_string;
   Label got_char_code;
+  Label sliced_string;
 
   // If the receiver is a smi trigger the non-string case.
   STATIC_ASSERT(kSmiTag == 0);
@@ -4769,31 +4871,45 @@
   __ j(zero, &flat_string);
 
   // Handle non-flat strings.
-  __ test(result_, Immediate(kIsConsStringMask));
-  __ j(zero, &call_runtime_);
+  __ and_(result_, kStringRepresentationMask);
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ cmp(result_, kExternalStringTag);
+  __ j(greater, &sliced_string, Label::kNear);
+  __ j(equal, &call_runtime_);
 
   // ConsString.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
+  Label assure_seq_string;
   __ cmp(FieldOperand(object_, ConsString::kSecondOffset),
          Immediate(masm->isolate()->factory()->empty_string()));
   __ j(not_equal, &call_runtime_);
   // Get the first of the two strings and load its instance type.
   __ mov(object_, FieldOperand(object_, ConsString::kFirstOffset));
+  __ jmp(&assure_seq_string, Label::kNear);
+
+  // SlicedString, unpack and add offset.
+  __ bind(&sliced_string);
+  __ add(scratch_, FieldOperand(object_, SlicedString::kOffsetOffset));
+  __ mov(object_, FieldOperand(object_, SlicedString::kParentOffset));
+
+  // Assure that we are dealing with a sequential string. Go to runtime if not.
+  __ bind(&assure_seq_string);
   __ mov(result_, FieldOperand(object_, HeapObject::kMapOffset));
   __ movzx_b(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
-  // If the first cons component is also non-flat, then go to runtime.
   STATIC_ASSERT(kSeqStringTag == 0);
   __ test(result_, Immediate(kStringRepresentationMask));
   __ j(not_zero, &call_runtime_);
+  __ jmp(&flat_string, Label::kNear);
 
   // Check for 1-byte or 2-byte string.
   __ bind(&flat_string);
   STATIC_ASSERT(kAsciiStringTag != 0);
   __ test(result_, Immediate(kStringEncodingMask));
-  __ j(not_zero, &ascii_string);
+  __ j(not_zero, &ascii_string, Label::kNear);
 
   // 2-byte string.
   // Load the 2-byte character code into the result register.
@@ -4801,7 +4917,7 @@
   __ movzx_w(result_, FieldOperand(object_,
                                    scratch_, times_1,  // Scratch is smi-tagged.
                                    SeqTwoByteString::kHeaderSize));
-  __ jmp(&got_char_code);
+  __ jmp(&got_char_code, Label::kNear);
 
   // ASCII string.
   // Load the byte into the result register.
@@ -5113,6 +5229,8 @@
   __ and_(ecx, kStringRepresentationMask);
   __ cmp(ecx, kExternalStringTag);
   __ j(equal, &string_add_runtime);
+  // We cannot encounter sliced strings here since:
+  STATIC_ASSERT(SlicedString::kMinLength >= String::kMinNonFlatLength);
   // Now check if both strings are ascii strings.
   // eax: first string
   // ebx: length of resulting flat string as a smi
@@ -5585,7 +5703,83 @@
   __ movzx_b(ebx, FieldOperand(ebx, Map::kInstanceTypeOffset));
   __ Set(ecx, Immediate(2));
 
-  __ bind(&result_longer_than_two);
+  if (FLAG_string_slices) {
+    Label copy_routine;
+    // If coming from the make_two_character_string path, the string
+    // is too short to be sliced anyways.
+    STATIC_ASSERT(2 < SlicedString::kMinLength);
+    __ jmp(&copy_routine);
+    __ bind(&result_longer_than_two);
+
+    // eax: string
+    // ebx: instance type
+    // ecx: sub string length
+    // edx: from index (smi)
+    Label allocate_slice, sliced_string, seq_string;
+    __ cmp(ecx, SlicedString::kMinLength);
+    // Short slice.  Copy instead of slicing.
+    __ j(less, &copy_routine);
+    STATIC_ASSERT(kSeqStringTag == 0);
+    __ test(ebx, Immediate(kStringRepresentationMask));
+    __ j(zero, &seq_string, Label::kNear);
+    STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
+    STATIC_ASSERT(kIsIndirectStringMask != 0);
+    __ test(ebx, Immediate(kIsIndirectStringMask));
+    // External string.  Jump to runtime.
+    __ j(zero, &runtime);
+
+    Factory* factory = masm->isolate()->factory();
+    __ test(ebx, Immediate(kSlicedNotConsMask));
+    __ j(not_zero, &sliced_string, Label::kNear);
+    // Cons string.  Check whether it is flat, then fetch first part.
+    __ cmp(FieldOperand(eax, ConsString::kSecondOffset),
+           factory->empty_string());
+    __ j(not_equal, &runtime);
+    __ mov(edi, FieldOperand(eax, ConsString::kFirstOffset));
+    __ jmp(&allocate_slice, Label::kNear);
+
+    __ bind(&sliced_string);
+    // Sliced string.  Fetch parent and correct start index by offset.
+    __ add(edx, FieldOperand(eax, SlicedString::kOffsetOffset));
+    __ mov(edi, FieldOperand(eax, SlicedString::kParentOffset));
+    __ jmp(&allocate_slice, Label::kNear);
+
+    __ bind(&seq_string);
+    // Sequential string.  Just move string to the right register.
+    __ mov(edi, eax);
+
+    __ bind(&allocate_slice);
+    // edi: underlying subject string
+    // ebx: instance type of original subject string
+    // edx: offset
+    // ecx: length
+    // Allocate new sliced string.  At this point we do not reload the instance
+    // type including the string encoding because we simply rely on the info
+    // provided by the original string.  It does not matter if the original
+    // string's encoding is wrong because we always have to recheck encoding of
+    // the newly created string's parent anyways due to externalized strings.
+    Label two_byte_slice, set_slice_header;
+    STATIC_ASSERT(kAsciiStringTag != 0);
+    __ test(ebx, Immediate(kAsciiStringTag));
+    __ j(zero, &two_byte_slice, Label::kNear);
+    __ AllocateAsciiSlicedString(eax, ebx, no_reg, &runtime);
+    __ jmp(&set_slice_header, Label::kNear);
+    __ bind(&two_byte_slice);
+    __ AllocateSlicedString(eax, ebx, no_reg, &runtime);
+    __ bind(&set_slice_header);
+    __ mov(FieldOperand(eax, SlicedString::kOffsetOffset), edx);
+    __ SmiTag(ecx);
+    __ mov(FieldOperand(eax, SlicedString::kLengthOffset), ecx);
+    __ mov(FieldOperand(eax, SlicedString::kParentOffset), edi);
+    __ mov(FieldOperand(eax, SlicedString::kHashFieldOffset),
+           Immediate(String::kEmptyHashField));
+    __ jmp(&return_eax);
+
+    __ bind(&copy_routine);
+  } else {
+    __ bind(&result_longer_than_two);
+  }
+
   // eax: string
   // ebx: instance type
   // ecx: result string length
diff --git a/src/ia32/deoptimizer-ia32.cc b/src/ia32/deoptimizer-ia32.cc
index 4ff1bfc..e23f3e9 100644
--- a/src/ia32/deoptimizer-ia32.cc
+++ b/src/ia32/deoptimizer-ia32.cc
@@ -37,7 +37,7 @@
 namespace v8 {
 namespace internal {
 
-int Deoptimizer::table_entry_size_ = 10;
+const int Deoptimizer::table_entry_size_ = 10;
 
 
 int Deoptimizer::patch_size() {
@@ -601,8 +601,6 @@
     output_frame->SetContinuation(
         reinterpret_cast<uint32_t>(continuation->entry()));
   }
-
-  if (output_count_ - 1 == frame_index) iterator->Done();
 }
 
 
diff --git a/src/ia32/disasm-ia32.cc b/src/ia32/disasm-ia32.cc
index 7a59a4f..a936277 100644
--- a/src/ia32/disasm-ia32.cc
+++ b/src/ia32/disasm-ia32.cc
@@ -54,7 +54,7 @@
 };
 
 
-static ByteMnemonic two_operands_instr[] = {
+static const ByteMnemonic two_operands_instr[] = {
   {0x03, "add", REG_OPER_OP_ORDER},
   {0x09, "or", OPER_REG_OP_ORDER},
   {0x0B, "or", REG_OPER_OP_ORDER},
@@ -79,7 +79,7 @@
 };
 
 
-static ByteMnemonic zero_operands_instr[] = {
+static const ByteMnemonic zero_operands_instr[] = {
   {0xC3, "ret", UNSET_OP_ORDER},
   {0xC9, "leave", UNSET_OP_ORDER},
   {0x90, "nop", UNSET_OP_ORDER},
@@ -98,14 +98,14 @@
 };
 
 
-static ByteMnemonic call_jump_instr[] = {
+static const ByteMnemonic call_jump_instr[] = {
   {0xE8, "call", UNSET_OP_ORDER},
   {0xE9, "jmp", UNSET_OP_ORDER},
   {-1, "", UNSET_OP_ORDER}
 };
 
 
-static ByteMnemonic short_immediate_instr[] = {
+static const ByteMnemonic short_immediate_instr[] = {
   {0x05, "add", UNSET_OP_ORDER},
   {0x0D, "or", UNSET_OP_ORDER},
   {0x15, "adc", UNSET_OP_ORDER},
@@ -117,7 +117,7 @@
 };
 
 
-static const char* jump_conditional_mnem[] = {
+static const char* const jump_conditional_mnem[] = {
   /*0*/ "jo", "jno", "jc", "jnc",
   /*4*/ "jz", "jnz", "jna", "ja",
   /*8*/ "js", "jns", "jpe", "jpo",
@@ -125,7 +125,7 @@
 };
 
 
-static const char* set_conditional_mnem[] = {
+static const char* const set_conditional_mnem[] = {
   /*0*/ "seto", "setno", "setc", "setnc",
   /*4*/ "setz", "setnz", "setna", "seta",
   /*8*/ "sets", "setns", "setpe", "setpo",
@@ -133,7 +133,7 @@
 };
 
 
-static const char* conditional_move_mnem[] = {
+static const char* const conditional_move_mnem[] = {
   /*0*/ "cmovo", "cmovno", "cmovc", "cmovnc",
   /*4*/ "cmovz", "cmovnz", "cmovna", "cmova",
   /*8*/ "cmovs", "cmovns", "cmovpe", "cmovpo",
@@ -169,7 +169,7 @@
   InstructionDesc instructions_[256];
   void Clear();
   void Init();
-  void CopyTable(ByteMnemonic bm[], InstructionType type);
+  void CopyTable(const ByteMnemonic bm[], InstructionType type);
   void SetTableRange(InstructionType type,
                      byte start,
                      byte end,
@@ -208,7 +208,8 @@
 }
 
 
-void InstructionTable::CopyTable(ByteMnemonic bm[], InstructionType type) {
+void InstructionTable::CopyTable(const ByteMnemonic bm[],
+                                 InstructionType type) {
   for (int i = 0; bm[i].b >= 0; i++) {
     InstructionDesc* id = &instructions_[bm[i].b];
     id->mnem = bm[i].mnem;
@@ -1140,7 +1141,17 @@
             }
           } else if (*data == 0x3A) {
             data++;
-            if (*data == 0x16) {
+            if (*data == 0x0B) {
+              data++;
+              int mod, regop, rm;
+              get_modrm(*data, &mod, &regop, &rm);
+              int8_t imm8 = static_cast<int8_t>(data[1]);
+              AppendToBuffer("roundsd %s,%s,%d",
+                             NameOfXMMRegister(regop),
+                             NameOfXMMRegister(rm),
+                             static_cast<int>(imm8));
+              data += 2;
+            } else if (*data == 0x16) {
               data++;
               int mod, regop, rm;
               get_modrm(*data, &mod, &regop, &rm);
diff --git a/src/ia32/frames-ia32.h b/src/ia32/frames-ia32.h
index bc65ddf..2f1b2a9 100644
--- a/src/ia32/frames-ia32.h
+++ b/src/ia32/frames-ia32.h
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -58,10 +58,11 @@
 
 class StackHandlerConstants : public AllStatic {
  public:
-  static const int kNextOffset  = 0 * kPointerSize;
-  static const int kFPOffset    = 1 * kPointerSize;
-  static const int kStateOffset = 2 * kPointerSize;
-  static const int kPCOffset    = 3 * kPointerSize;
+  static const int kNextOffset    = 0 * kPointerSize;
+  static const int kContextOffset = 1 * kPointerSize;
+  static const int kFPOffset      = 2 * kPointerSize;
+  static const int kStateOffset   = 3 * kPointerSize;
+  static const int kPCOffset      = 4 * kPointerSize;
 
   static const int kSize = kPCOffset + kPointerSize;
 };
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index 7633856..df2542e 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -46,7 +46,6 @@
 
 
 static unsigned GetPropertyId(Property* property) {
-  if (property->is_synthetic()) return AstNode::kNoNumber;
   return property->id();
 }
 
@@ -166,6 +165,11 @@
     }
   }
 
+  set_stack_height(2 + scope()->num_stack_slots());
+  if (FLAG_verify_stack_height) {
+    verify_stack_height();
+  }
+
   bool function_in_register = true;
 
   // Possibly allocate a local context.
@@ -358,6 +362,15 @@
 }
 
 
+void FullCodeGenerator::verify_stack_height() {
+  ASSERT(FLAG_verify_stack_height);
+  __ sub(Operand(ebp), Immediate(kPointerSize * stack_height()));
+  __ cmp(ebp, Operand(esp));
+  __ Assert(equal, "Full codegen stack height not as expected.");
+  __ add(Operand(ebp), Immediate(kPointerSize * stack_height()));
+}
+
+
 void FullCodeGenerator::EffectContext::Plug(Slot* slot) const {
 }
 
@@ -372,6 +385,7 @@
   MemOperand slot_operand = codegen()->EmitSlotSearch(slot, result_register());
   // Memory operands can be pushed directly.
   __ push(slot_operand);
+  codegen()->increment_stack_height();
 }
 
 
@@ -425,6 +439,7 @@
   } else {
     __ push(Immediate(lit));
   }
+  codegen()->increment_stack_height();
 }
 
 
@@ -462,6 +477,7 @@
                                                    Register reg) const {
   ASSERT(count > 0);
   __ Drop(count);
+  codegen()->decrement_stack_height(count);
 }
 
 
@@ -471,6 +487,7 @@
   ASSERT(count > 0);
   __ Drop(count);
   __ Move(result_register(), reg);
+  codegen()->decrement_stack_height(count);
 }
 
 
@@ -479,6 +496,7 @@
   ASSERT(count > 0);
   if (count > 1) __ Drop(count - 1);
   __ mov(Operand(esp, 0), reg);
+  codegen()->decrement_stack_height(count - 1);
 }
 
 
@@ -490,6 +508,7 @@
   __ Move(result_register(), reg);
   codegen()->PrepareForBailoutBeforeSplit(TOS_REG, false, NULL, NULL);
   codegen()->DoTest(this);
+  codegen()->decrement_stack_height(count);
 }
 
 
@@ -523,6 +542,7 @@
   __ bind(materialize_false);
   __ push(Immediate(isolate()->factory()->false_value()));
   __ bind(&done);
+  codegen()->increment_stack_height();
 }
 
 
@@ -550,6 +570,7 @@
       ? isolate()->factory()->true_value()
       : isolate()->factory()->false_value();
   __ push(Immediate(value));
+  codegen()->increment_stack_height();
 }
 
 
@@ -572,7 +593,7 @@
                                Label* fall_through) {
   ToBooleanStub stub(result_register());
   __ push(result_register());
-  __ CallStub(&stub);
+  __ CallStub(&stub, condition->test_id());
   __ test(result_register(), Operand(result_register()));
   // The stub returns nonzero for true.
   Split(not_zero, if_true, if_false, fall_through);
@@ -668,97 +689,73 @@
   Comment cmnt(masm_, "[ Declaration");
   ASSERT(variable != NULL);  // Must have been resolved.
   Slot* slot = variable->AsSlot();
-  Property* prop = variable->AsProperty();
-
-  if (slot != NULL) {
-    switch (slot->type()) {
-      case Slot::PARAMETER:
-      case Slot::LOCAL:
-        if (mode == Variable::CONST) {
-          __ mov(Operand(ebp, SlotOffset(slot)),
-                 Immediate(isolate()->factory()->the_hole_value()));
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ mov(Operand(ebp, SlotOffset(slot)), result_register());
-        }
-        break;
-
-      case Slot::CONTEXT:
-        // We bypass the general EmitSlotSearch because we know more about
-        // this specific context.
-
-        // The variable in the decl always resides in the current function
-        // context.
-        ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
-        if (FLAG_debug_code) {
-          // Check that we're not inside a with or catch context.
-          __ mov(ebx, FieldOperand(esi, HeapObject::kMapOffset));
-          __ cmp(ebx, isolate()->factory()->with_context_map());
-          __ Check(not_equal, "Declaration in with context.");
-          __ cmp(ebx, isolate()->factory()->catch_context_map());
-          __ Check(not_equal, "Declaration in catch context.");
-        }
-        if (mode == Variable::CONST) {
-          __ mov(ContextOperand(esi, slot->index()),
-                 Immediate(isolate()->factory()->the_hole_value()));
-          // No write barrier since the hole value is in old space.
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ mov(ContextOperand(esi, slot->index()), result_register());
-          int offset = Context::SlotOffset(slot->index());
-          __ mov(ebx, esi);
-          __ RecordWrite(ebx, offset, result_register(), ecx);
-        }
-        break;
-
-      case Slot::LOOKUP: {
-        __ push(esi);
-        __ push(Immediate(variable->name()));
-        // Declaration nodes are always introduced in one of two modes.
-        ASSERT(mode == Variable::VAR || mode == Variable::CONST);
-        PropertyAttributes attr = (mode == Variable::VAR) ? NONE : READ_ONLY;
-        __ push(Immediate(Smi::FromInt(attr)));
-        // Push initial value, if any.
-        // Note: For variables we must not push an initial value (such as
-        // 'undefined') because we may have a (legal) redeclaration and we
-        // must not destroy the current value.
-        if (mode == Variable::CONST) {
-          __ push(Immediate(isolate()->factory()->the_hole_value()));
-        } else if (function != NULL) {
-          VisitForStackValue(function);
-        } else {
-          __ push(Immediate(Smi::FromInt(0)));  // No initial value!
-        }
-        __ CallRuntime(Runtime::kDeclareContextSlot, 4);
-        break;
+  ASSERT(slot != NULL);
+  switch (slot->type()) {
+    case Slot::PARAMETER:
+    case Slot::LOCAL:
+      if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ mov(Operand(ebp, SlotOffset(slot)), result_register());
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ mov(Operand(ebp, SlotOffset(slot)),
+               Immediate(isolate()->factory()->the_hole_value()));
       }
-    }
+      break;
 
-  } else if (prop != NULL) {
-    // A const declaration aliasing a parameter is an illegal redeclaration.
-    ASSERT(mode != Variable::CONST);
-    if (function != NULL) {
-      // We are declaring a function that rewrites to a property.
-      // Use (keyed) IC to set the initial value.  We cannot visit the
-      // rewrite because it's shared and we risk recording duplicate AST
-      // IDs for bailouts from optimized code.
-      ASSERT(prop->obj()->AsVariableProxy() != NULL);
-      { AccumulatorValueContext for_object(this);
-        EmitVariableLoad(prop->obj()->AsVariableProxy());
+    case Slot::CONTEXT:
+      // We bypass the general EmitSlotSearch because we know more about
+      // this specific context.
+
+      // The variable in the decl always resides in the current function
+      // context.
+      ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
+      if (FLAG_debug_code) {
+        // Check that we're not inside a with or catch context.
+        __ mov(ebx, FieldOperand(esi, HeapObject::kMapOffset));
+        __ cmp(ebx, isolate()->factory()->with_context_map());
+        __ Check(not_equal, "Declaration in with context.");
+        __ cmp(ebx, isolate()->factory()->catch_context_map());
+        __ Check(not_equal, "Declaration in catch context.");
       }
+      if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ mov(ContextOperand(esi, slot->index()), result_register());
+        int offset = Context::SlotOffset(slot->index());
+        __ mov(ebx, esi);
+        __ RecordWrite(ebx, offset, result_register(), ecx);
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ mov(ContextOperand(esi, slot->index()),
+               Immediate(isolate()->factory()->the_hole_value()));
+        // No write barrier since the hole value is in old space.
+      }
+      break;
 
-      __ push(eax);
-      VisitForAccumulatorValue(function);
-      __ pop(edx);
-
-      ASSERT(prop->key()->AsLiteral() != NULL &&
-             prop->key()->AsLiteral()->handle()->IsSmi());
-      __ SafeSet(ecx, Immediate(prop->key()->AsLiteral()->handle()));
-
-      Handle<Code> ic = is_strict_mode()
-          ? isolate()->builtins()->KeyedStoreIC_Initialize_Strict()
-          : isolate()->builtins()->KeyedStoreIC_Initialize();
-      __ call(ic);
+    case Slot::LOOKUP: {
+      __ push(esi);
+      __ push(Immediate(variable->name()));
+      // Declaration nodes are always introduced in one of two modes.
+      ASSERT(mode == Variable::VAR ||
+             mode == Variable::CONST ||
+             mode == Variable::LET);
+      PropertyAttributes attr = (mode == Variable::CONST) ? READ_ONLY : NONE;
+      __ push(Immediate(Smi::FromInt(attr)));
+      // Push initial value, if any.
+      // Note: For variables we must not push an initial value (such as
+      // 'undefined') because we may have a (legal) redeclaration and we
+      // must not destroy the current value.
+      increment_stack_height(3);
+      if (function != NULL) {
+        VisitForStackValue(function);
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ push(Immediate(isolate()->factory()->the_hole_value()));
+        increment_stack_height();
+      } else {
+        __ push(Immediate(Smi::FromInt(0)));  // No initial value!
+        increment_stack_height();
+      }
+      __ CallRuntime(Runtime::kDeclareContextSlot, 4);
+      decrement_stack_height(4);
+      break;
     }
   }
 }
@@ -785,6 +782,7 @@
   Breakable nested_statement(this, stmt);
   SetStatementPosition(stmt);
 
+  int switch_clause_stack_height = stack_height();
   // Keep the switch value on the stack until a case matches.
   VisitForStackValue(stmt->tag());
   PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
@@ -844,11 +842,12 @@
   __ bind(&next_test);
   __ Drop(1);  // Switch value is no longer needed.
   if (default_clause == NULL) {
-    __ jmp(nested_statement.break_target());
+    __ jmp(nested_statement.break_label());
   } else {
     __ jmp(default_clause->body_target());
   }
 
+  set_stack_height(switch_clause_stack_height);
   // Compile all the case bodies.
   for (int i = 0; i < clauses->length(); i++) {
     Comment cmnt(masm_, "[ Case body");
@@ -858,7 +857,7 @@
     VisitStatements(clause->statements());
   }
 
-  __ bind(nested_statement.break_target());
+  __ bind(nested_statement.break_label());
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
 }
 
@@ -890,6 +889,7 @@
   __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
   __ bind(&done_convert);
   __ push(eax);
+  increment_stack_height();
 
   // Check cache validity in generated code. This is a fast case for
   // the JSObject::IsSimpleEnum cache validity checks. If we cannot
@@ -973,11 +973,13 @@
   __ push(eax);  // Fixed array length (as smi).
   __ push(Immediate(Smi::FromInt(0)));  // Initial index.
 
+  // 1 ~ The object has already been pushed.
+  increment_stack_height(ForIn::kElementCount - 1);
   // Generate code for doing the condition check.
   __ bind(&loop);
   __ mov(eax, Operand(esp, 0 * kPointerSize));  // Get the current index.
   __ cmp(eax, Operand(esp, 1 * kPointerSize));  // Compare to the array length.
-  __ j(above_equal, loop_statement.break_target());
+  __ j(above_equal, loop_statement.break_label());
 
   // Get the current entry of the array into register ebx.
   __ mov(ebx, Operand(esp, 2 * kPointerSize));
@@ -1001,7 +1003,7 @@
   __ push(ebx);  // Current entry.
   __ InvokeBuiltin(Builtins::FILTER_KEY, CALL_FUNCTION);
   __ test(eax, Operand(eax));
-  __ j(equal, loop_statement.continue_target());
+  __ j(equal, loop_statement.continue_label());
   __ mov(ebx, Operand(eax));
 
   // Update the 'each' property or variable from the possibly filtered
@@ -1018,16 +1020,17 @@
 
   // Generate code for going to the next element by incrementing the
   // index (smi) stored on top of the stack.
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   __ add(Operand(esp, 0 * kPointerSize), Immediate(Smi::FromInt(1)));
 
   EmitStackCheck(stmt);
   __ jmp(&loop);
 
   // Remove the pointers stored on the stack.
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   __ add(Operand(esp), Immediate(5 * kPointerSize));
 
+  decrement_stack_height(ForIn::kElementCount);
   // Exit and decrement the loop depth.
   __ bind(&exit);
   decrement_loop_depth();
@@ -1265,6 +1268,18 @@
       __ mov(eax, isolate()->factory()->undefined_value());
       __ bind(&done);
       context()->Plug(eax);
+    } else if (var->mode() == Variable::LET) {
+      // Let bindings may be the hole value if they have not been initialized.
+      // Throw a type error in this case.
+      Label done;
+      MemOperand slot_operand = EmitSlotSearch(slot, eax);
+      __ mov(eax, slot_operand);
+      __ cmp(eax, isolate()->factory()->the_hole_value());
+      __ j(not_equal, &done, Label::kNear);
+      __ push(Immediate(var->name()));
+      __ CallRuntime(Runtime::kThrowReferenceError, 1);
+      __ bind(&done);
+      context()->Plug(eax);
     } else {
       context()->Plug(slot);
     }
@@ -1363,6 +1378,7 @@
     if (!result_saved) {
       __ push(eax);  // Save result on the stack
       result_saved = true;
+      increment_stack_height();
     }
     switch (property->kind()) {
       case ObjectLiteral::Property::MATERIALIZED_LITERAL:
@@ -1387,6 +1403,7 @@
         // Fall through.
       case ObjectLiteral::Property::PROTOTYPE:
         __ push(Operand(esp, 0));  // Duplicate receiver.
+        increment_stack_height();
         VisitForStackValue(key);
         VisitForStackValue(value);
         if (property->emit_store()) {
@@ -1395,16 +1412,20 @@
         } else {
           __ Drop(3);
         }
+        decrement_stack_height(3);
         break;
       case ObjectLiteral::Property::SETTER:
       case ObjectLiteral::Property::GETTER:
         __ push(Operand(esp, 0));  // Duplicate receiver.
+        increment_stack_height();
         VisitForStackValue(key);
         __ push(Immediate(property->kind() == ObjectLiteral::Property::SETTER ?
                           Smi::FromInt(1) :
                           Smi::FromInt(0)));
+        increment_stack_height();
         VisitForStackValue(value);
         __ CallRuntime(Runtime::kDefineAccessor, 4);
+        decrement_stack_height(4);
         break;
       default: UNREACHABLE();
     }
@@ -1467,6 +1488,7 @@
     if (!result_saved) {
       __ push(eax);
       result_saved = true;
+      increment_stack_height();
     }
     VisitForAccumulatorValue(subexpr);
 
@@ -1495,7 +1517,9 @@
   // Invalid left-hand sides are rewritten to have a 'throw ReferenceError'
   // on the left-hand side.
   if (!expr->target()->IsValidLeftHandSide()) {
-    VisitForEffect(expr->target());
+    ASSERT(expr->target()->AsThrow() != NULL);
+    VisitInCurrentContext(expr->target());  // Throw does not plug the context
+    context()->Plug(eax);
     return;
   }
 
@@ -1520,6 +1544,7 @@
         // We need the receiver both on the stack and in the accumulator.
         VisitForAccumulatorValue(property->obj());
         __ push(result_register());
+        increment_stack_height();
       } else {
         VisitForStackValue(property->obj());
       }
@@ -1530,6 +1555,7 @@
         VisitForAccumulatorValue(property->key());
         __ mov(edx, Operand(esp, 0));
         __ push(eax);
+        increment_stack_height();
       } else {
         VisitForStackValue(property->obj());
         VisitForStackValue(property->key());
@@ -1541,7 +1567,8 @@
   // For compound assignments we need another deoptimization point after the
   // variable/property load.
   if (expr->is_compound()) {
-    { AccumulatorValueContext context(this);
+    AccumulatorValueContext result_context(this);
+    { AccumulatorValueContext left_operand_context(this);
       switch (assign_type) {
         case VARIABLE:
           EmitVariableLoad(expr->target()->AsVariableProxy());
@@ -1560,13 +1587,13 @@
 
     Token::Value op = expr->binary_op();
     __ push(eax);  // Left operand goes on the stack.
+    increment_stack_height();
     VisitForAccumulatorValue(expr->value());
 
     OverwriteMode mode = expr->value()->ResultOverwriteAllowed()
         ? OVERWRITE_RIGHT
         : NO_OVERWRITE;
     SetSourcePosition(expr->position() + 1);
-    AccumulatorValueContext context(this);
     if (ShouldInlineSmiCase(op)) {
       EmitInlineSmiBinaryOp(expr->binary_operation(),
                             op,
@@ -1630,6 +1657,7 @@
   // stack. Right operand is in eax.
   Label smi_case, done, stub_call;
   __ pop(edx);
+  decrement_stack_height();
   __ mov(ecx, eax);
   __ or_(eax, Operand(edx));
   JumpPatchSite patch_site(masm_);
@@ -1721,6 +1749,7 @@
                                      Token::Value op,
                                      OverwriteMode mode) {
   __ pop(edx);
+  decrement_stack_height();
   BinaryOpStub stub(op, mode);
   JumpPatchSite patch_site(masm_);    // unbound, signals no inlined smi code.
   __ call(stub.GetCode(), RelocInfo::CODE_TARGET, expr->id());
@@ -1733,7 +1762,9 @@
   // Invalid left-hand sides are rewritten to have a 'throw
   // ReferenceError' on the left-hand side.
   if (!expr->IsValidLeftHandSide()) {
-    VisitForEffect(expr);
+    ASSERT(expr->AsThrow() != NULL);
+    VisitInCurrentContext(expr);  // Throw does not plug the context
+    context()->Plug(eax);
     return;
   }
 
@@ -1757,9 +1788,11 @@
     }
     case NAMED_PROPERTY: {
       __ push(eax);  // Preserve value.
+      increment_stack_height();
       VisitForAccumulatorValue(prop->obj());
       __ mov(edx, eax);
       __ pop(eax);  // Restore value.
+      decrement_stack_height();
       __ mov(ecx, prop->key()->AsLiteral()->handle());
       Handle<Code> ic = is_strict_mode()
           ? isolate()->builtins()->StoreIC_Initialize_Strict()
@@ -1769,21 +1802,14 @@
     }
     case KEYED_PROPERTY: {
       __ push(eax);  // Preserve value.
-      if (prop->is_synthetic()) {
-        ASSERT(prop->obj()->AsVariableProxy() != NULL);
-        ASSERT(prop->key()->AsLiteral() != NULL);
-        { AccumulatorValueContext for_object(this);
-          EmitVariableLoad(prop->obj()->AsVariableProxy());
-        }
-        __ mov(edx, eax);
-        __ SafeSet(ecx, Immediate(prop->key()->AsLiteral()->handle()));
-      } else {
-        VisitForStackValue(prop->obj());
-        VisitForAccumulatorValue(prop->key());
-        __ mov(ecx, eax);
-        __ pop(edx);
-      }
+      increment_stack_height();
+      VisitForStackValue(prop->obj());
+      VisitForAccumulatorValue(prop->key());
+      __ mov(ecx, eax);
+      __ pop(edx);
+      decrement_stack_height();
       __ pop(eax);  // Restore value.
+      decrement_stack_height();
       Handle<Code> ic = is_strict_mode()
           ? isolate()->builtins()->KeyedStoreIC_Initialize_Strict()
           : isolate()->builtins()->KeyedStoreIC_Initialize();
@@ -1841,6 +1867,57 @@
     }
     __ bind(&skip);
 
+  } else if (var->mode() == Variable::LET && op != Token::INIT_LET) {
+    // Perform the assignment for non-const variables.  Const assignments
+    // are simply skipped.
+    Slot* slot = var->AsSlot();
+    switch (slot->type()) {
+      case Slot::PARAMETER:
+      case Slot::LOCAL: {
+        Label assign;
+        // Check for an initialized let binding.
+        __ mov(edx, Operand(ebp, SlotOffset(slot)));
+        __ cmp(edx, isolate()->factory()->the_hole_value());
+        __ j(not_equal, &assign);
+        __ push(Immediate(var->name()));
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+        // Perform the assignment.
+        __ bind(&assign);
+        __ mov(Operand(ebp, SlotOffset(slot)), eax);
+        break;
+      }
+
+      case Slot::CONTEXT: {
+        // Let variables may be the hole value if they have not been
+        // initialized. Throw a type error in this case.
+        Label assign;
+        MemOperand target = EmitSlotSearch(slot, ecx);
+        // Check for an initialized let binding.
+        __ mov(edx, target);
+        __ cmp(edx, isolate()->factory()->the_hole_value());
+        __ j(not_equal, &assign, Label::kNear);
+        __ push(Immediate(var->name()));
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+        // Perform the assignment.
+        __ bind(&assign);
+        __ mov(target, eax);
+        // The value of the assignment is in eax. RecordWrite clobbers its
+        // register arguments.
+        __ mov(edx, eax);
+        int offset = Context::SlotOffset(slot->index());
+        __ RecordWrite(ecx, offset, edx, ebx);
+        break;
+      }
+
+      case Slot::LOOKUP:
+        // Call the runtime for the assignment.
+        __ push(eax);  // Value.
+        __ push(esi);  // Context.
+        __ push(Immediate(var->name()));
+        __ push(Immediate(Smi::FromInt(strict_mode_flag())));
+        __ CallRuntime(Runtime::kStoreContextSlot, 4);
+        break;
+    }
   } else if (var->mode() != Variable::CONST) {
     // Perform the assignment for non-const variables.  Const assignments
     // are simply skipped.
@@ -1900,6 +1977,7 @@
     __ mov(edx, Operand(esp, 0));
   } else {
     __ pop(edx);
+    decrement_stack_height();
   }
   Handle<Code> ic = is_strict_mode()
       ? isolate()->builtins()->StoreIC_Initialize_Strict()
@@ -1913,6 +1991,7 @@
     __ CallRuntime(Runtime::kToFastProperties, 1);
     __ pop(eax);
     __ Drop(1);
+    decrement_stack_height();
   }
   PrepareForBailoutForId(expr->AssignmentId(), TOS_REG);
   context()->Plug(eax);
@@ -1934,10 +2013,12 @@
   }
 
   __ pop(ecx);
+  decrement_stack_height();
   if (expr->ends_initialization_block()) {
     __ mov(edx, Operand(esp, 0));  // Leave receiver on the stack for later.
   } else {
     __ pop(edx);
+    decrement_stack_height();
   }
   // Record source code position before IC call.
   SetSourcePosition(expr->position());
@@ -1953,6 +2034,7 @@
     __ push(edx);
     __ CallRuntime(Runtime::kToFastProperties, 1);
     __ pop(eax);
+    decrement_stack_height();
   }
 
   PrepareForBailoutForId(expr->AssignmentId(), TOS_REG);
@@ -1972,6 +2054,7 @@
     VisitForStackValue(expr->obj());
     VisitForAccumulatorValue(expr->key());
     __ pop(edx);
+    decrement_stack_height();
     EmitKeyedPropertyLoad(expr);
     context()->Plug(eax);
   }
@@ -1999,6 +2082,7 @@
   RecordJSReturnSite(expr);
   // Restore context register.
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+  decrement_stack_height(arg_count + 1);
   context()->Plug(eax);
 }
 
@@ -2013,6 +2097,7 @@
   __ pop(ecx);
   __ push(eax);
   __ push(ecx);
+  increment_stack_height();
 
   // Load the arguments.
   ZoneList<Expression*>* args = expr->arguments();
@@ -2032,6 +2117,7 @@
   RecordJSReturnSite(expr);
   // Restore context register.
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+  decrement_stack_height(arg_count + 1);
   context()->DropAndPlug(1, eax);  // Drop the key still on the stack.
 }
 
@@ -2053,6 +2139,8 @@
   RecordJSReturnSite(expr);
   // Restore context register.
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+
+  decrement_stack_height(arg_count + 1);
   context()->DropAndPlug(1, eax);
 }
 
@@ -2100,7 +2188,7 @@
       VisitForStackValue(fun);
       // Reserved receiver slot.
       __ push(Immediate(isolate()->factory()->undefined_value()));
-
+      increment_stack_height();
       // Push the arguments.
       for (int i = 0; i < arg_count; i++) {
         VisitForStackValue(args->at(i));
@@ -2144,10 +2232,12 @@
     RecordJSReturnSite(expr);
     // Restore context register.
     __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+    decrement_stack_height(arg_count + 1);  // Function is left on the stack.
     context()->DropAndPlug(1, eax);
   } else if (var != NULL && !var->is_this() && var->is_global()) {
     // Push global object as receiver for the call IC.
     __ push(GlobalObjectOperand());
+    increment_stack_height();
     EmitCallWithIC(expr, var->name(), RelocInfo::CODE_TARGET_CONTEXT);
   } else if (var != NULL && var->AsSlot() != NULL &&
              var->AsSlot()->type() == Slot::LOOKUP) {
@@ -2170,7 +2260,9 @@
     __ push(Immediate(var->name()));
     __ CallRuntime(Runtime::kLoadContextSlot, 2);
     __ push(eax);  // Function.
+    increment_stack_height();
     __ push(edx);  // Receiver.
+    increment_stack_height();
 
     // If fast case code has been generated, emit code to push the
     // function and receiver and have the slow path jump around this
@@ -2179,7 +2271,7 @@
       Label call;
       __ jmp(&call);
       __ bind(&done);
-      // Push function.
+      // Push function.  Stack height already incremented in slow case above.
       __ push(eax);
       // The receiver is implicitly the global receiver. Indicate this
       // by passing the hole to the call function stub.
@@ -2203,38 +2295,10 @@
       EmitCallWithIC(expr, key->handle(), RelocInfo::CODE_TARGET);
     } else {
       // Call to a keyed property.
-      // For a synthetic property use keyed load IC followed by function call,
-      // for a regular property use EmitKeyedCallWithIC.
-      if (prop->is_synthetic()) {
-        // Do not visit the object and key subexpressions (they are shared
-        // by all occurrences of the same rewritten parameter).
-        ASSERT(prop->obj()->AsVariableProxy() != NULL);
-        ASSERT(prop->obj()->AsVariableProxy()->var()->AsSlot() != NULL);
-        Slot* slot = prop->obj()->AsVariableProxy()->var()->AsSlot();
-        MemOperand operand = EmitSlotSearch(slot, edx);
-        __ mov(edx, operand);
-
-        ASSERT(prop->key()->AsLiteral() != NULL);
-        ASSERT(prop->key()->AsLiteral()->handle()->IsSmi());
-        __ mov(eax, prop->key()->AsLiteral()->handle());
-
-        // Record source code position for IC call.
-        SetSourcePosition(prop->position());
-
-        Handle<Code> ic = isolate()->builtins()->KeyedLoadIC_Initialize();
-        __ call(ic, RelocInfo::CODE_TARGET, GetPropertyId(prop));
-        // Push result (function).
-        __ push(eax);
-        // Push Global receiver.
-        __ mov(ecx, GlobalObjectOperand());
-        __ push(FieldOperand(ecx, GlobalObject::kGlobalReceiverOffset));
-        EmitCallWithStub(expr, NO_CALL_FUNCTION_FLAGS);
-      } else {
-        { PreservePositionScope scope(masm()->positions_recorder());
-          VisitForStackValue(prop->obj());
-        }
-        EmitKeyedCallWithIC(expr, prop->key());
+      { PreservePositionScope scope(masm()->positions_recorder());
+        VisitForStackValue(prop->obj());
       }
+      EmitKeyedCallWithIC(expr, prop->key());
     }
   } else {
     { PreservePositionScope scope(masm()->positions_recorder());
@@ -2243,6 +2307,7 @@
     // Load global receiver object.
     __ mov(ebx, GlobalObjectOperand());
     __ push(FieldOperand(ebx, GlobalObject::kGlobalReceiverOffset));
+    increment_stack_height();
     // Emit function call.
     EmitCallWithStub(expr, NO_CALL_FUNCTION_FLAGS);
   }
@@ -2283,6 +2348,8 @@
   Handle<Code> construct_builtin =
       isolate()->builtins()->JSConstructCall();
   __ call(construct_builtin, RelocInfo::CONSTRUCT_CALL);
+
+  decrement_stack_height(arg_count + 1);
   context()->Plug(eax);
 }
 
@@ -2595,6 +2662,7 @@
                          &if_true, &if_false, &fall_through);
 
   __ pop(ebx);
+  decrement_stack_height();
   __ cmp(eax, Operand(ebx));
   PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
   Split(equal, if_true, if_false, fall_through);
@@ -2709,6 +2777,7 @@
     VisitForStackValue(args->at(1));
     VisitForStackValue(args->at(2));
     __ CallRuntime(Runtime::kLog, 2);
+    decrement_stack_height(2);
   }
   // Finally, we're expected to leave a value on the top of the stack.
   __ mov(eax, isolate()->factory()->undefined_value());
@@ -2774,6 +2843,7 @@
   VisitForStackValue(args->at(1));
   VisitForStackValue(args->at(2));
   __ CallStub(&stub);
+  decrement_stack_height(3);
   context()->Plug(eax);
 }
 
@@ -2787,6 +2857,7 @@
   VisitForStackValue(args->at(2));
   VisitForStackValue(args->at(3));
   __ CallStub(&stub);
+  decrement_stack_height(4);
   context()->Plug(eax);
 }
 
@@ -2821,6 +2892,7 @@
   } else {
     __ CallRuntime(Runtime::kMath_pow, 2);
   }
+  decrement_stack_height(2);
   context()->Plug(eax);
 }
 
@@ -2831,6 +2903,7 @@
   VisitForStackValue(args->at(0));  // Load the object.
   VisitForAccumulatorValue(args->at(1));  // Load the value.
   __ pop(ebx);  // eax = value. ebx = object.
+  decrement_stack_height();
 
   Label done;
   // If the object is a smi, return the value.
@@ -2860,6 +2933,7 @@
 
   NumberToStringStub stub;
   __ CallStub(&stub);
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
@@ -2894,6 +2968,7 @@
   Register result = edx;
 
   __ pop(object);
+  decrement_stack_height();
 
   Label need_conversion;
   Label index_out_of_range;
@@ -2942,6 +3017,7 @@
   Register result = eax;
 
   __ pop(object);
+  decrement_stack_height();
 
   Label need_conversion;
   Label index_out_of_range;
@@ -2986,6 +3062,7 @@
 
   StringAddStub stub(NO_STRING_ADD_FLAGS);
   __ CallStub(&stub);
+  decrement_stack_height(2);
   context()->Plug(eax);
 }
 
@@ -2998,6 +3075,7 @@
 
   StringCompareStub stub;
   __ CallStub(&stub);
+  decrement_stack_height(2);
   context()->Plug(eax);
 }
 
@@ -3009,6 +3087,7 @@
   ASSERT(args->length() == 1);
   VisitForStackValue(args->at(0));
   __ CallStub(&stub);
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
@@ -3020,6 +3099,7 @@
   ASSERT(args->length() == 1);
   VisitForStackValue(args->at(0));
   __ CallStub(&stub);
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
@@ -3031,6 +3111,7 @@
   ASSERT(args->length() == 1);
   VisitForStackValue(args->at(0));
   __ CallStub(&stub);
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
@@ -3040,6 +3121,7 @@
   ASSERT(args->length() == 1);
   VisitForStackValue(args->at(0));
   __ CallRuntime(Runtime::kMath_sqrt, 1);
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
@@ -3059,6 +3141,7 @@
   __ InvokeFunction(edi, count, CALL_FUNCTION,
                     NullCallWrapper(), CALL_AS_METHOD);
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+  decrement_stack_height(arg_count + 1);
   context()->Plug(eax);
 }
 
@@ -3071,6 +3154,7 @@
   VisitForStackValue(args->at(1));
   VisitForStackValue(args->at(2));
   __ CallStub(&stub);
+  decrement_stack_height(3);
   context()->Plug(eax);
 }
 
@@ -3144,6 +3228,7 @@
   __ CallRuntime(Runtime::kSwapElements, 3);
 
   __ bind(&done);
+  decrement_stack_height(3);
   context()->Plug(eax);
 }
 
@@ -3177,7 +3262,7 @@
 
   Label done, not_found;
   // tmp now holds finger offset as a smi.
-  ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
   __ mov(tmp, FieldOperand(cache, JSFunctionResultCache::kFingerOffset));
   __ cmp(key, CodeGenerator::FixedArrayElementOperand(cache, tmp));
   __ j(not_equal, &not_found);
@@ -3229,6 +3314,7 @@
   __ mov(eax, Immediate(isolate()->factory()->true_value()));
   __ bind(&done);
 
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
@@ -3532,43 +3618,11 @@
   __ add(Operand(esp), Immediate(3 * kPointerSize));
 
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+  decrement_stack_height();
   context()->Plug(eax);
 }
 
 
-void FullCodeGenerator::EmitIsNativeOrStrictMode(ZoneList<Expression*>* args) {
-  ASSERT(args->length() == 1);
-
-  // Load the function into eax.
-  VisitForAccumulatorValue(args->at(0));
-
-  // Prepare for the test.
-  Label materialize_true, materialize_false;
-  Label* if_true = NULL;
-  Label* if_false = NULL;
-  Label* fall_through = NULL;
-  context()->PrepareTest(&materialize_true, &materialize_false,
-                         &if_true, &if_false, &fall_through);
-
-  // Test for strict mode function.
-  __ mov(ecx, FieldOperand(eax, JSFunction::kSharedFunctionInfoOffset));
-  __ test_b(FieldOperand(ecx, SharedFunctionInfo::kStrictModeByteOffset),
-            1 << SharedFunctionInfo::kStrictModeBitWithinByte);
-  __ j(not_equal, if_true);
-
-  // Test for native function.
-  __ test_b(FieldOperand(ecx, SharedFunctionInfo::kNativeByteOffset),
-            1 << SharedFunctionInfo::kNativeBitWithinByte);
-  __ j(not_equal, if_true);
-
-  // Not native or strict-mode function.
-  __ jmp(if_false);
-
-  PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
-  context()->Plug(if_true, if_false);
-}
-
-
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   Handle<String> name = expr->name();
   if (name->length() > 0 && name->Get(0) == '_') {
@@ -3584,6 +3638,7 @@
     // Prepare for calling JS runtime function.
     __ mov(eax, GlobalObjectOperand());
     __ push(FieldOperand(eax, GlobalObject::kBuiltinsOffset));
+    increment_stack_height();
   }
 
   // Push the arguments ("left-to-right").
@@ -3606,6 +3661,11 @@
     // Call the C runtime function.
     __ CallRuntime(expr->function(), arg_count);
   }
+  decrement_stack_height(arg_count);
+  if (expr->is_jsruntime()) {
+    decrement_stack_height();
+  }
+
   context()->Plug(eax);
 }
 
@@ -3618,17 +3678,12 @@
       Variable* var = expr->expression()->AsVariableProxy()->AsVariable();
 
       if (prop != NULL) {
-        if (prop->is_synthetic()) {
-          // Result of deleting parameters is false, even when they rewrite
-          // to accesses on the arguments object.
-          context()->Plug(false);
-        } else {
-          VisitForStackValue(prop->obj());
-          VisitForStackValue(prop->key());
-          __ push(Immediate(Smi::FromInt(strict_mode_flag())));
-          __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
-          context()->Plug(eax);
-        }
+        VisitForStackValue(prop->obj());
+        VisitForStackValue(prop->key());
+        __ push(Immediate(Smi::FromInt(strict_mode_flag())));
+        __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
+        decrement_stack_height(2);
+        context()->Plug(eax);
       } else if (var != NULL) {
         // Delete of an unqualified identifier is disallowed in strict mode
         // but "delete this" is.
@@ -3696,6 +3751,7 @@
         VisitForTypeofValue(expr->expression());
       }
       __ CallRuntime(Runtime::kTypeof, 1);
+      decrement_stack_height();
       context()->Plug(eax);
       break;
     }
@@ -3728,7 +3784,6 @@
 
 void FullCodeGenerator::EmitUnaryOperation(UnaryOperation* expr,
                                            const char* comment) {
-  // TODO(svenpanne): Allowing format strings in Comment would be nice here...
   Comment cmt(masm_, comment);
   bool can_overwrite = expr->expression()->ResultOverwriteAllowed();
   UnaryOverwriteMode overwrite =
@@ -3750,7 +3805,10 @@
   // Invalid left-hand sides are rewritten to have a 'throw ReferenceError'
   // as the left-hand side.
   if (!expr->expression()->IsValidLeftHandSide()) {
-    VisitForEffect(expr->expression());
+    ASSERT(expr->expression()->AsThrow() != NULL);
+    VisitInCurrentContext(expr->expression());
+    // Visiting Throw does not plug the context.
+    context()->Plug(eax);
     return;
   }
 
@@ -3775,17 +3833,20 @@
     // Reserve space for result of postfix operation.
     if (expr->is_postfix() && !context()->IsEffect()) {
       __ push(Immediate(Smi::FromInt(0)));
+      increment_stack_height();
     }
     if (assign_type == NAMED_PROPERTY) {
       // Put the object both on the stack and in the accumulator.
       VisitForAccumulatorValue(prop->obj());
       __ push(eax);
+      increment_stack_height();
       EmitNamedPropertyLoad(prop);
     } else {
       VisitForStackValue(prop->obj());
       VisitForAccumulatorValue(prop->key());
       __ mov(edx, Operand(esp, 0));
       __ push(eax);
+      increment_stack_height();
       EmitKeyedPropertyLoad(prop);
     }
   }
@@ -3816,6 +3877,7 @@
       switch (assign_type) {
         case VARIABLE:
           __ push(eax);
+          increment_stack_height();
           break;
         case NAMED_PROPERTY:
           __ mov(Operand(esp, kPointerSize), eax);
@@ -3889,6 +3951,7 @@
     case NAMED_PROPERTY: {
       __ mov(ecx, prop->key()->AsLiteral()->handle());
       __ pop(edx);
+      decrement_stack_height();
       Handle<Code> ic = is_strict_mode()
           ? isolate()->builtins()->StoreIC_Initialize_Strict()
           : isolate()->builtins()->StoreIC_Initialize();
@@ -3906,6 +3969,8 @@
     case KEYED_PROPERTY: {
       __ pop(ecx);
       __ pop(edx);
+      decrement_stack_height();
+      decrement_stack_height();
       Handle<Code> ic = is_strict_mode()
           ? isolate()->builtins()->KeyedStoreIC_Initialize_Strict()
           : isolate()->builtins()->KeyedStoreIC_Initialize();
@@ -3993,6 +4058,10 @@
     __ j(equal, if_true);
     __ cmp(eax, isolate()->factory()->false_value());
     Split(equal, if_true, if_false, fall_through);
+  } else if (FLAG_harmony_typeof &&
+             check->Equals(isolate()->heap()->null_symbol())) {
+    __ cmp(eax, isolate()->factory()->null_value());
+    Split(equal, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->undefined_symbol())) {
     __ cmp(eax, isolate()->factory()->undefined_value());
     __ j(equal, if_true);
@@ -4008,8 +4077,10 @@
     Split(above_equal, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->object_symbol())) {
     __ JumpIfSmi(eax, if_false);
-    __ cmp(eax, isolate()->factory()->null_value());
-    __ j(equal, if_true);
+    if (!FLAG_harmony_typeof) {
+      __ cmp(eax, isolate()->factory()->null_value());
+      __ j(equal, if_true);
+    }
     __ CmpObjectType(eax, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, edx);
     __ j(below, if_false);
     __ CmpInstanceType(edx, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
@@ -4063,6 +4134,7 @@
     case Token::IN:
       VisitForStackValue(expr->right());
       __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION);
+      decrement_stack_height(2);
       PrepareForBailoutBeforeSplit(TOS_REG, false, NULL, NULL);
       __ cmp(eax, isolate()->factory()->true_value());
       Split(equal, if_true, if_false, fall_through);
@@ -4072,6 +4144,7 @@
       VisitForStackValue(expr->right());
       InstanceofStub stub(InstanceofStub::kNoFlags);
       __ CallStub(&stub);
+      decrement_stack_height(2);
       PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
       __ test(eax, Operand(eax));
       // The stub returns 0 for true.
@@ -4113,6 +4186,7 @@
         default:
           UNREACHABLE();
       }
+      decrement_stack_height();
 
       bool inline_smi_code = ShouldInlineSmiCase(op);
       JumpPatchSite patch_site(masm_);
@@ -4228,8 +4302,8 @@
   ASSERT(!result_register().is(edx));
   __ pop(edx);
   __ sub(Operand(edx), Immediate(masm_->CodeObject()));
-  ASSERT_EQ(1, kSmiTagSize + kSmiShiftSize);
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 1);
+  STATIC_ASSERT(kSmiTag == 0);
   __ SmiTag(edx);
   __ push(edx);
   // Store result register while executing finally block.
@@ -4250,6 +4324,34 @@
 
 #undef __
 
+#define __ ACCESS_MASM(masm())
+
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
+    int* stack_depth,
+    int* context_length) {
+  // The macros used here must preserve the result register.
+
+  // Because the handler block contains the context of the finally
+  // code, we can restore it directly from there for the finally code
+  // rather than iteratively unwinding contexts via their previous
+  // links.
+  __ Drop(*stack_depth);  // Down to the handler block.
+  if (*context_length > 0) {
+    // Restore the context to its dedicated register and the stack.
+    __ mov(esi, Operand(esp, StackHandlerConstants::kContextOffset));
+    __ mov(Operand(ebp, StandardFrameConstants::kContextOffset), esi);
+  }
+  __ PopTryHandler();
+  __ call(finally_entry_);
+
+  *stack_depth = 0;
+  *context_length = 0;
+  return previous_;
+}
+
+
+#undef __
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32
diff --git a/src/ia32/ic-ia32.cc b/src/ia32/ic-ia32.cc
index 5f143b1..7d3ead2 100644
--- a/src/ia32/ic-ia32.cc
+++ b/src/ia32/ic-ia32.cc
@@ -324,7 +324,7 @@
   __ cmp(key, FieldOperand(scratch, FixedArray::kLengthOffset));
   __ j(above_equal, out_of_range);
   // Fast case: Do the load.
-  ASSERT((kPointerSize == 4) && (kSmiTagSize == 1) && (kSmiTag == 0));
+  STATIC_ASSERT((kPointerSize == 4) && (kSmiTagSize == 1) && (kSmiTag == 0));
   __ mov(scratch, FieldOperand(scratch, key, times_2, FixedArray::kHeaderSize));
   __ cmp(Operand(scratch), Immediate(FACTORY->the_hole_value()));
   // In case the loaded value is the_hole we have to consult GetProperty
@@ -358,7 +358,7 @@
   __ j(zero, index_string);
 
   // Is the string a symbol?
-  ASSERT(kSymbolTag != 0);
+  STATIC_ASSERT(kSymbolTag != 0);
   __ test_b(FieldOperand(map, Map::kInstanceTypeOffset), kIsSymbolMask);
   __ j(zero, not_symbol);
 }
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 982eddb..32e3074 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -1211,17 +1211,11 @@
 }
 
 
-void LCodeGen::DoFixedArrayLength(LFixedArrayLength* instr) {
+void LCodeGen::DoFixedArrayBaseLength(
+    LFixedArrayBaseLength* instr) {
   Register result = ToRegister(instr->result());
   Register array = ToRegister(instr->InputAt(0));
-  __ mov(result, FieldOperand(array, FixedArray::kLengthOffset));
-}
-
-
-void LCodeGen::DoExternalArrayLength(LExternalArrayLength* instr) {
-  Register result = ToRegister(instr->result());
-  Register array = ToRegister(instr->InputAt(0));
-  __ mov(result, FieldOperand(array, ExternalArray::kLengthOffset));
+  __ mov(result, FieldOperand(array, FixedArrayBase::kLengthOffset));
 }
 
 
@@ -1393,44 +1387,98 @@
   } else {
     ASSERT(r.IsTagged());
     Register reg = ToRegister(instr->InputAt(0));
-    if (instr->hydrogen()->value()->type().IsBoolean()) {
+    HType type = instr->hydrogen()->value()->type();
+    if (type.IsBoolean()) {
       __ cmp(reg, factory()->true_value());
       EmitBranch(true_block, false_block, equal);
+    } else if (type.IsSmi()) {
+      __ test(reg, Operand(reg));
+      EmitBranch(true_block, false_block, not_equal);
     } else {
       Label* true_label = chunk_->GetAssemblyLabel(true_block);
       Label* false_label = chunk_->GetAssemblyLabel(false_block);
 
-      __ cmp(reg, factory()->undefined_value());
-      __ j(equal, false_label);
-      __ cmp(reg, factory()->true_value());
-      __ j(equal, true_label);
-      __ cmp(reg, factory()->false_value());
-      __ j(equal, false_label);
-      __ test(reg, Operand(reg));
-      __ j(equal, false_label);
-      __ JumpIfSmi(reg, true_label);
+      ToBooleanStub::Types expected = instr->hydrogen()->expected_input_types();
+      // Avoid deopts in the case where we've never executed this path before.
+      if (expected.IsEmpty()) expected = ToBooleanStub::all_types();
 
-      // Test for double values. Zero is false.
-      Label call_stub;
-      __ cmp(FieldOperand(reg, HeapObject::kMapOffset),
-             factory()->heap_number_map());
-      __ j(not_equal, &call_stub, Label::kNear);
-      __ fldz();
-      __ fld_d(FieldOperand(reg, HeapNumber::kValueOffset));
-      __ FCmp();
-      __ j(zero, false_label);
-      __ jmp(true_label);
+      if (expected.Contains(ToBooleanStub::UNDEFINED)) {
+        // undefined -> false.
+        __ cmp(reg, factory()->undefined_value());
+        __ j(equal, false_label);
+      }
+      if (expected.Contains(ToBooleanStub::BOOLEAN)) {
+        // true -> true.
+        __ cmp(reg, factory()->true_value());
+        __ j(equal, true_label);
+        // false -> false.
+        __ cmp(reg, factory()->false_value());
+        __ j(equal, false_label);
+      }
+      if (expected.Contains(ToBooleanStub::NULL_TYPE)) {
+        // 'null' -> false.
+        __ cmp(reg, factory()->null_value());
+        __ j(equal, false_label);
+      }
 
-      // The conversion stub doesn't cause garbage collections so it's
-      // safe to not record a safepoint after the call.
-      __ bind(&call_stub);
-      ToBooleanStub stub(eax);
-      __ pushad();
-      __ push(reg);
-      __ CallStub(&stub);
-      __ test(eax, Operand(eax));
-      __ popad();
-      EmitBranch(true_block, false_block, not_zero);
+      if (expected.Contains(ToBooleanStub::SMI)) {
+        // Smis: 0 -> false, all other -> true.
+        __ test(reg, Operand(reg));
+        __ j(equal, false_label);
+        __ JumpIfSmi(reg, true_label);
+      } else if (expected.NeedsMap()) {
+        // If we need a map later and have a Smi -> deopt.
+        __ test(reg, Immediate(kSmiTagMask));
+        DeoptimizeIf(zero, instr->environment());
+      }
+
+      Register map = no_reg;  // Keep the compiler happy.
+      if (expected.NeedsMap()) {
+        map = ToRegister(instr->TempAt(0));
+        ASSERT(!map.is(reg));
+        __ mov(map, FieldOperand(reg, HeapObject::kMapOffset));
+
+        if (expected.CanBeUndetectable()) {
+          // Undetectable -> false.
+          __ test_b(FieldOperand(map, Map::kBitFieldOffset),
+                    1 << Map::kIsUndetectable);
+          __ j(not_zero, false_label);
+        }
+      }
+
+      if (expected.Contains(ToBooleanStub::SPEC_OBJECT)) {
+        // spec object -> true.
+        __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
+        __ j(above_equal, true_label);
+      }
+
+      if (expected.Contains(ToBooleanStub::STRING)) {
+        // String value -> false iff empty.
+        Label not_string;
+        __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
+        __ j(above_equal, &not_string, Label::kNear);
+        __ cmp(FieldOperand(reg, String::kLengthOffset), Immediate(0));
+        __ j(not_zero, true_label);
+        __ jmp(false_label);
+        __ bind(&not_string);
+      }
+
+      if (expected.Contains(ToBooleanStub::HEAP_NUMBER)) {
+        // heap number -> false iff +0, -0, or NaN.
+        Label not_heap_number;
+        __ cmp(FieldOperand(reg, HeapObject::kMapOffset),
+               factory()->heap_number_map());
+        __ j(not_equal, &not_heap_number, Label::kNear);
+        __ fldz();
+        __ fld_d(FieldOperand(reg, HeapNumber::kValueOffset));
+        __ FCmp();
+        __ j(zero, false_label);
+        __ jmp(true_label);
+        __ bind(&not_heap_number);
+      }
+
+      // We've seen something for the first time -> deopt.
+      DeoptimizeIf(no_condition, instr->environment());
     }
   }
 }
@@ -2211,16 +2259,13 @@
 
 
 void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
-  Register elements = ToRegister(instr->elements());
-  Register key = ToRegister(instr->key());
   Register result = ToRegister(instr->result());
-  ASSERT(result.is(elements));
 
   // Load the result.
-  __ mov(result, FieldOperand(elements,
-                              key,
-                              times_pointer_size,
-                              FixedArray::kHeaderSize));
+  __ mov(result,
+         BuildFastArrayOperand(instr->elements(), instr->key(),
+                               JSObject::FAST_ELEMENTS,
+                               FixedArray::kHeaderSize - kHeapObjectTag));
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
@@ -2253,22 +2298,22 @@
 
 
 Operand LCodeGen::BuildFastArrayOperand(
-    LOperand* external_pointer,
+    LOperand* elements_pointer,
     LOperand* key,
     JSObject::ElementsKind elements_kind,
     uint32_t offset) {
-  Register external_pointer_reg = ToRegister(external_pointer);
+  Register elements_pointer_reg = ToRegister(elements_pointer);
   int shift_size = ElementsKindToShiftSize(elements_kind);
   if (key->IsConstantOperand()) {
     int constant_value = ToInteger32(LConstantOperand::cast(key));
     if (constant_value & 0xF0000000) {
       Abort("array index constant value too big");
     }
-    return Operand(external_pointer_reg,
+    return Operand(elements_pointer_reg,
                    constant_value * (1 << shift_size) + offset);
   } else {
     ScaleFactor scale_factor = static_cast<ScaleFactor>(shift_size);
-    return Operand(external_pointer_reg, ToRegister(key), scale_factor, offset);
+    return Operand(elements_pointer_reg, ToRegister(key), scale_factor, offset);
   }
 }
 
@@ -2665,24 +2710,54 @@
   XMMRegister xmm_scratch = xmm0;
   Register output_reg = ToRegister(instr->result());
   XMMRegister input_reg = ToDoubleRegister(instr->value());
-  __ xorps(xmm_scratch, xmm_scratch);  // Zero the register.
-  __ ucomisd(input_reg, xmm_scratch);
 
-  if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
-    DeoptimizeIf(below_equal, instr->environment());
+  if (CpuFeatures::IsSupported(SSE4_1)) {
+    CpuFeatures::Scope scope(SSE4_1);
+    if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
+      // Deoptimize on negative zero.
+      Label non_zero;
+      __ xorps(xmm_scratch, xmm_scratch);  // Zero the register.
+      __ ucomisd(input_reg, xmm_scratch);
+      __ j(not_equal, &non_zero, Label::kNear);
+      __ movmskpd(output_reg, input_reg);
+      __ test(output_reg, Immediate(1));
+      DeoptimizeIf(not_zero, instr->environment());
+      __ bind(&non_zero);
+    }
+    __ roundsd(xmm_scratch, input_reg, Assembler::kRoundDown);
+    __ cvttsd2si(output_reg, Operand(xmm_scratch));
+    // Overflow is signalled with minint.
+    __ cmp(output_reg, 0x80000000u);
+    DeoptimizeIf(equal, instr->environment());
   } else {
+    Label done;
+    // Deoptimize on negative numbers.
+    __ xorps(xmm_scratch, xmm_scratch);  // Zero the register.
+    __ ucomisd(input_reg, xmm_scratch);
     DeoptimizeIf(below, instr->environment());
+
+    if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
+      // Check for negative zero.
+      Label positive_sign;
+      __ j(above, &positive_sign, Label::kNear);
+      __ movmskpd(output_reg, input_reg);
+      __ test(output_reg, Immediate(1));
+      DeoptimizeIf(not_zero, instr->environment());
+      __ Set(output_reg, Immediate(0));
+      __ jmp(&done, Label::kNear);
+      __ bind(&positive_sign);
+    }
+
+    // Use truncating instruction (OK because input is positive).
+    __ cvttsd2si(output_reg, Operand(input_reg));
+
+    // Overflow is signalled with minint.
+    __ cmp(output_reg, 0x80000000u);
+    DeoptimizeIf(equal, instr->environment());
+    __ bind(&done);
   }
-
-  // Use truncating instruction (OK because input is positive).
-  __ cvttsd2si(output_reg, Operand(input_reg));
-
-  // Overflow is signalled with minint.
-  __ cmp(output_reg, 0x80000000u);
-  DeoptimizeIf(equal, instr->environment());
 }
 
-
 void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
   XMMRegister xmm_scratch = xmm0;
   Register output_reg = ToRegister(instr->result());
@@ -2692,13 +2767,11 @@
   // xmm_scratch = 0.5
   ExternalReference one_half = ExternalReference::address_of_one_half();
   __ movdbl(xmm_scratch, Operand::StaticVariable(one_half));
-
   __ ucomisd(xmm_scratch, input_reg);
   __ j(above, &below_half);
   // input = input + 0.5
   __ addsd(input_reg, xmm_scratch);
 
-
   // Compute Math.floor(value + 0.5).
   // Use truncating instruction (OK because input is positive).
   __ cvttsd2si(output_reg, Operand(input_reg));
@@ -3017,8 +3090,14 @@
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  __ cmp(ToRegister(instr->index()), ToOperand(instr->length()));
-  DeoptimizeIf(above_equal, instr->environment());
+  if (instr->index()->IsConstantOperand()) {
+    __ cmp(ToOperand(instr->length()),
+           ToImmediate(LConstantOperand::cast(instr->index())));
+    DeoptimizeIf(below_equal, instr->environment());
+  } else {
+    __ cmp(ToRegister(instr->index()), ToOperand(instr->length()));
+    DeoptimizeIf(above_equal, instr->environment());
+  }
 }
 
 
@@ -3096,6 +3175,7 @@
 void LCodeGen::DoStoreKeyedFastDoubleElement(
     LStoreKeyedFastDoubleElement* instr) {
   XMMRegister value = ToDoubleRegister(instr->value());
+  Register key = instr->key()->IsRegister() ? ToRegister(instr->key()) : no_reg;
   Label have_value;
 
   __ ucomisd(value, value);
@@ -3137,95 +3217,79 @@
   };
 
   Register string = ToRegister(instr->string());
-  Register index = no_reg;
-  int const_index = -1;
-  if (instr->index()->IsConstantOperand()) {
-    const_index = ToInteger32(LConstantOperand::cast(instr->index()));
-    STATIC_ASSERT(String::kMaxLength <= Smi::kMaxValue);
-    if (!Smi::IsValid(const_index)) {
-      // Guaranteed to be out of bounds because of the assert above.
-      // So the bounds check that must dominate this instruction must
-      // have deoptimized already.
-      if (FLAG_debug_code) {
-        __ Abort("StringCharCodeAt: out of bounds index.");
-      }
-      // No code needs to be generated.
-      return;
-    }
-  } else {
-    index = ToRegister(instr->index());
-  }
+  Register index = ToRegister(instr->index());
   Register result = ToRegister(instr->result());
 
   DeferredStringCharCodeAt* deferred =
       new DeferredStringCharCodeAt(this, instr);
 
-  Label flat_string, ascii_string, done;
-
   // Fetch the instance type of the receiver into result register.
   __ mov(result, FieldOperand(string, HeapObject::kMapOffset));
   __ movzx_b(result, FieldOperand(result, Map::kInstanceTypeOffset));
 
-  // We need special handling for non-flat strings.
-  STATIC_ASSERT(kSeqStringTag == 0);
-  __ test(result, Immediate(kStringRepresentationMask));
-  __ j(zero, &flat_string, Label::kNear);
+  // We need special handling for indirect strings.
+  Label check_sequential;
+  __ test(result, Immediate(kIsIndirectStringMask));
+  __ j(zero, &check_sequential, Label::kNear);
 
-  // Handle non-flat strings.
-  __ test(result, Immediate(kIsConsStringMask));
-  __ j(zero, deferred->entry());
+  // Dispatch on the indirect string shape: slice or cons.
+  Label cons_string;
+  __ test(result, Immediate(kSlicedNotConsMask));
+  __ j(zero, &cons_string, Label::kNear);
 
-  // ConsString.
+  // Handle slices.
+  Label indirect_string_loaded;
+  __ mov(result, FieldOperand(string, SlicedString::kOffsetOffset));
+  __ SmiUntag(result);
+  __ add(index, Operand(result));
+  __ mov(string, FieldOperand(string, SlicedString::kParentOffset));
+  __ jmp(&indirect_string_loaded, Label::kNear);
+
+  // Handle conses.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
+  __ bind(&cons_string);
   __ cmp(FieldOperand(string, ConsString::kSecondOffset),
          Immediate(factory()->empty_string()));
   __ j(not_equal, deferred->entry());
-  // Get the first of the two strings and load its instance type.
   __ mov(string, FieldOperand(string, ConsString::kFirstOffset));
+
+  __ bind(&indirect_string_loaded);
   __ mov(result, FieldOperand(string, HeapObject::kMapOffset));
   __ movzx_b(result, FieldOperand(result, Map::kInstanceTypeOffset));
-  // If the first cons component is also non-flat, then go to runtime.
+
+  // Check whether the string is sequential. The only non-sequential
+  // shapes we support have just been unwrapped above.
+  __ bind(&check_sequential);
   STATIC_ASSERT(kSeqStringTag == 0);
   __ test(result, Immediate(kStringRepresentationMask));
   __ j(not_zero, deferred->entry());
 
-  // Check for ASCII or two-byte string.
-  __ bind(&flat_string);
+  // Dispatch on the encoding: ASCII or two-byte.
+  Label ascii_string;
   STATIC_ASSERT(kAsciiStringTag != 0);
   __ test(result, Immediate(kStringEncodingMask));
   __ j(not_zero, &ascii_string, Label::kNear);
 
   // Two-byte string.
   // Load the two-byte character code into the result register.
+  Label done;
   STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
-  if (instr->index()->IsConstantOperand()) {
-    __ movzx_w(result,
-               FieldOperand(string,
-                            SeqTwoByteString::kHeaderSize +
-                            (kUC16Size * const_index)));
-  } else {
-    __ movzx_w(result, FieldOperand(string,
-                                    index,
-                                    times_2,
-                                    SeqTwoByteString::kHeaderSize));
-  }
+  __ movzx_w(result, FieldOperand(string,
+                                  index,
+                                  times_2,
+                                  SeqTwoByteString::kHeaderSize));
   __ jmp(&done, Label::kNear);
 
   // ASCII string.
   // Load the byte into the result register.
   __ bind(&ascii_string);
-  if (instr->index()->IsConstantOperand()) {
-    __ movzx_b(result, FieldOperand(string,
-                                    SeqAsciiString::kHeaderSize + const_index));
-  } else {
-    __ movzx_b(result, FieldOperand(string,
-                                    index,
-                                    times_1,
-                                    SeqAsciiString::kHeaderSize));
-  }
+  __ movzx_b(result, FieldOperand(string,
+                                  index,
+                                  times_1,
+                                  SeqAsciiString::kHeaderSize));
   __ bind(&done);
   __ bind(deferred->exit());
 }
@@ -4108,6 +4172,10 @@
     __ cmp(input, factory()->false_value());
     final_branch_condition = equal;
 
+  } else if (FLAG_harmony_typeof && type_name->Equals(heap()->null_symbol())) {
+    __ cmp(input, factory()->null_value());
+    final_branch_condition = equal;
+
   } else if (type_name->Equals(heap()->undefined_symbol())) {
     __ cmp(input, factory()->undefined_value());
     __ j(equal, true_label);
@@ -4126,8 +4194,10 @@
 
   } else if (type_name->Equals(heap()->object_symbol())) {
     __ JumpIfSmi(input, false_label);
-    __ cmp(input, factory()->null_value());
-    __ j(equal, true_label);
+    if (!FLAG_harmony_typeof) {
+      __ cmp(input, factory()->null_value());
+      __ j(equal, true_label);
+    }
     __ CmpObjectType(input, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, input);
     __ j(below, false_label);
     __ CmpInstanceType(input, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
diff --git a/src/ia32/lithium-codegen-ia32.h b/src/ia32/lithium-codegen-ia32.h
index c568bef..d26f245 100644
--- a/src/ia32/lithium-codegen-ia32.h
+++ b/src/ia32/lithium-codegen-ia32.h
@@ -222,7 +222,7 @@
   Register ToRegister(int index) const;
   XMMRegister ToDoubleRegister(int index) const;
   int ToInteger32(LConstantOperand* op) const;
-  Operand BuildFastArrayOperand(LOperand* external_pointer,
+  Operand BuildFastArrayOperand(LOperand* elements_pointer,
                                 LOperand* key,
                                 JSObject::ElementsKind elements_kind,
                                 uint32_t offset);
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index f0615ef..f59ee07 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1045,7 +1045,13 @@
         : instr->SecondSuccessor();
     return new LGoto(successor->block_id());
   }
-  return new LBranch(UseRegisterAtStart(v));
+  ToBooleanStub::Types expected = instr->expected_input_types();
+  // We need a temporary register when we have to access the map *or* we have
+  // no type info yet, in which case we handle all cases (including the ones
+  // involving maps).
+  bool needs_temp = expected.NeedsMap() || expected.IsEmpty();
+  LOperand* temp = needs_temp ? TempRegister() : NULL;
+  return AssignEnvironment(new LBranch(UseRegister(v), temp));
 }
 
 
@@ -1536,16 +1542,10 @@
 }
 
 
-LInstruction* LChunkBuilder::DoFixedArrayLength(HFixedArrayLength* instr) {
+LInstruction* LChunkBuilder::DoFixedArrayBaseLength(
+    HFixedArrayBaseLength* instr) {
   LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LFixedArrayLength(array));
-}
-
-
-LInstruction* LChunkBuilder::DoExternalArrayLength(
-    HExternalArrayLength* instr) {
-  LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LExternalArrayLength(array));
+  return DefineAsRegister(new LFixedArrayBaseLength(array));
 }
 
 
@@ -1563,8 +1563,9 @@
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
-  return AssignEnvironment(new LBoundsCheck(UseRegisterAtStart(instr->index()),
-                                            UseAtStart(instr->length())));
+  return AssignEnvironment(new LBoundsCheck(
+      UseRegisterOrConstantAtStart(instr->index()),
+      UseAtStart(instr->length())));
 }
 
 
@@ -1885,9 +1886,9 @@
   ASSERT(instr->representation().IsTagged());
   ASSERT(instr->key()->representation().IsInteger32());
   LOperand* obj = UseRegisterAtStart(instr->object());
-  LOperand* key = UseRegisterAtStart(instr->key());
+  LOperand* key = UseRegisterOrConstantAtStart(instr->key());
   LLoadKeyedFastElement* result = new LLoadKeyedFastElement(obj, key);
-  return AssignEnvironment(DefineSameAsFirst(result));
+  return AssignEnvironment(DefineAsRegister(result));
 }
 
 
@@ -2061,8 +2062,8 @@
 
 
 LInstruction* LChunkBuilder::DoStringCharCodeAt(HStringCharCodeAt* instr) {
-  LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegisterOrConstant(instr->index());
+  LOperand* string = UseTempRegister(instr->string());
+  LOperand* index = UseTempRegister(instr->index());
   LOperand* context = UseAny(instr->context());
   LStringCharCodeAt* result = new LStringCharCodeAt(context, string, index);
   return AssignEnvironment(AssignPointerMap(DefineAsRegister(result)));
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index 0ea7c6b..4b407a3 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -86,8 +86,7 @@
   V(DivI)                                       \
   V(DoubleToI)                                  \
   V(ElementsKind)                               \
-  V(ExternalArrayLength)                        \
-  V(FixedArrayLength)                           \
+  V(FixedArrayBaseLength)                       \
   V(FunctionLiteral)                            \
   V(GetCachedArrayIndex)                        \
   V(GlobalObject)                               \
@@ -876,10 +875,11 @@
 };
 
 
-class LBranch: public LControlInstruction<1, 0> {
+class LBranch: public LControlInstruction<1, 1> {
  public:
-  explicit LBranch(LOperand* value) {
+  explicit LBranch(LOperand* value, LOperand* temp) {
     inputs_[0] = value;
+    temps_[0] = temp;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(Branch, "branch")
@@ -921,25 +921,15 @@
 };
 
 
-class LExternalArrayLength: public LTemplateInstruction<1, 1, 0> {
+class LFixedArrayBaseLength: public LTemplateInstruction<1, 1, 0> {
  public:
-  explicit LExternalArrayLength(LOperand* value) {
+  explicit LFixedArrayBaseLength(LOperand* value) {
     inputs_[0] = value;
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(ExternalArrayLength, "external-array-length")
-  DECLARE_HYDROGEN_ACCESSOR(ExternalArrayLength)
-};
-
-
-class LFixedArrayLength: public LTemplateInstruction<1, 1, 0> {
- public:
-  explicit LFixedArrayLength(LOperand* value) {
-    inputs_[0] = value;
-  }
-
-  DECLARE_CONCRETE_INSTRUCTION(FixedArrayLength, "fixed-array-length")
-  DECLARE_HYDROGEN_ACCESSOR(FixedArrayLength)
+  DECLARE_CONCRETE_INSTRUCTION(FixedArrayBaseLength,
+                               "fixed-array-base-length")
+  DECLARE_HYDROGEN_ACCESSOR(FixedArrayBaseLength)
 };
 
 
@@ -2247,14 +2237,18 @@
   template<int I, int T>
       LInstruction* DefineFixedDouble(LTemplateInstruction<1, I, T>* instr,
                                       XMMRegister reg);
+  // Assigns an environment to an instruction.  An instruction which can
+  // deoptimize must have an environment.
   LInstruction* AssignEnvironment(LInstruction* instr);
+  // Assigns a pointer map to an instruction.  An instruction which can
+  // trigger a GC or a lazy deoptimization must have a pointer map.
   LInstruction* AssignPointerMap(LInstruction* instr);
 
   enum CanDeoptimize { CAN_DEOPTIMIZE_EAGERLY, CANNOT_DEOPTIMIZE_EAGERLY };
 
-  // By default we assume that instruction sequences generated for calls
-  // cannot deoptimize eagerly and we do not attach environment to this
-  // instruction.
+  // Marks a call for the register allocator.  Assigns a pointer map to
+  // support GC and lazy deoptimization.  Assigns an environment to support
+  // eager deoptimization if CAN_DEOPTIMIZE_EAGERLY.
   LInstruction* MarkAsCall(
       LInstruction* instr,
       HInstruction* hinstr,
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 3e037d7..dff174c 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -69,8 +69,8 @@
 
   // Compute number of region covering addr. See Page::GetRegionNumberForAddress
   // method for more details.
-  and_(addr, Page::kPageAlignmentMask);
   shr(addr, Page::kRegionSizeLog2);
+  and_(addr, Page::kPageAlignmentMask >> Page::kRegionSizeLog2);
 
   // Set dirty mark for region.
   // Bit tests with a memory operand should be avoided on Intel processors,
@@ -148,7 +148,7 @@
   Label done;
 
   // Skip barrier if writing a smi.
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   JumpIfSmi(value, &done, Label::kNear);
 
   InNewSpace(object, value, equal, &done, Label::kNear);
@@ -166,8 +166,8 @@
     // Array access: calculate the destination address in the same manner as
     // KeyedStoreIC::GenerateGeneric.  Multiply a smi by 2 to get an offset
     // into an array of words.
-    ASSERT_EQ(1, kSmiTagSize);
-    ASSERT_EQ(0, kSmiTag);
+    STATIC_ASSERT(kSmiTagSize == 1);
+    STATIC_ASSERT(kSmiTag == 0);
     lea(dst, Operand(object, dst, times_half_pointer_size,
                      FixedArray::kHeaderSize - kHeapObjectTag));
   }
@@ -193,7 +193,7 @@
   Label done;
 
   // Skip barrier if writing a smi.
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   JumpIfSmi(value, &done, Label::kNear);
 
   InNewSpace(object, value, equal, &done);
@@ -263,6 +263,13 @@
 }
 
 
+void MacroAssembler::CompareRoot(Register with, Heap::RootListIndex index) {
+  // see ROOT_ACCESSOR macro in factory.h
+  Handle<Object> value(&isolate()->heap()->roots_address()[index]);
+  cmp(with, value);
+}
+
+
 void MacroAssembler::CmpObjectType(Register heap_object,
                                    InstanceType type,
                                    Register map) {
@@ -319,7 +326,7 @@
                                              Register instance_type) {
   mov(map, FieldOperand(heap_object, HeapObject::kMapOffset));
   movzx_b(instance_type, FieldOperand(map, Map::kInstanceTypeOffset));
-  ASSERT(kNotStringTag != 0);
+  STATIC_ASSERT(kNotStringTag != 0);
   test(instance_type, Immediate(kIsNotStringMask));
   return zero;
 }
@@ -535,7 +542,12 @@
 void MacroAssembler::PushTryHandler(CodeLocation try_location,
                                     HandlerType type) {
   // Adjust this code if not the case.
-  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // The pc (return address) is already on TOS.
   if (try_location == IN_JAVASCRIPT) {
     if (type == TRY_CATCH_HANDLER) {
@@ -544,6 +556,7 @@
       push(Immediate(StackHandler::TRY_FINALLY));
     }
     push(ebp);
+    push(esi);
   } else {
     ASSERT(try_location == IN_JS_ENTRY);
     // The frame pointer does not point to a JS frame so we save NULL
@@ -551,6 +564,7 @@
     // before dereferencing it to restore the context.
     push(Immediate(StackHandler::ENTRY));
     push(Immediate(0));  // NULL frame pointer.
+    push(Immediate(Smi::FromInt(0)));  // No context.
   }
   // Save the current handler as the next handler.
   push(Operand::StaticVariable(ExternalReference(Isolate::k_handler_address,
@@ -563,7 +577,7 @@
 
 
 void MacroAssembler::PopTryHandler() {
-  ASSERT_EQ(0, StackHandlerConstants::kNextOffset);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(Operand::StaticVariable(ExternalReference(Isolate::k_handler_address,
                                                 isolate())));
   add(Operand(esp), Immediate(StackHandlerConstants::kSize - kPointerSize));
@@ -572,8 +586,12 @@
 
 void MacroAssembler::Throw(Register value) {
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
-
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // eax must hold the exception.
   if (!value.is(eax)) {
     mov(eax, value);
@@ -584,24 +602,21 @@
                                     isolate());
   mov(esp, Operand::StaticVariable(handler_address));
 
-  // Restore next handler and frame pointer, discard handler state.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  // Restore next handler, context, and frame pointer; discard handler state.
   pop(Operand::StaticVariable(handler_address));
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 1 * kPointerSize);
-  pop(ebp);
-  pop(edx);  // Remove state.
+  pop(esi);  // Context.
+  pop(ebp);  // Frame pointer.
+  pop(edx);  // State.
 
-  // Before returning we restore the context from the frame pointer if
-  // not NULL.  The frame pointer is NULL in the exception handler of
-  // a JS entry frame.
-  Set(esi, Immediate(0));  // Tentatively set context pointer to NULL.
+  // If the handler is a JS frame, restore the context to the frame.
+  // (edx == ENTRY) == (ebp == 0) == (esi == 0), so we could test any
+  // of them.
   Label skip;
-  cmp(ebp, 0);
+  cmp(Operand(edx), Immediate(StackHandler::ENTRY));
   j(equal, &skip, Label::kNear);
-  mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+  mov(Operand(ebp, StandardFrameConstants::kContextOffset), esi);
   bind(&skip);
 
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   ret(0);
 }
 
@@ -609,7 +624,12 @@
 void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
                                       Register value) {
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
 
   // eax must hold the exception.
   if (!value.is(eax)) {
@@ -635,7 +655,6 @@
   bind(&done);
 
   // Set the top handler address to next handler past the current ENTRY handler.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(Operand::StaticVariable(handler_address));
 
   if (type == OUT_OF_MEMORY) {
@@ -653,15 +672,14 @@
     mov(Operand::StaticVariable(pending_exception), eax);
   }
 
-  // Clear the context pointer.
+  // Discard the context saved in the handler and clear the context pointer.
+  pop(edx);
   Set(esi, Immediate(0));
 
   // Restore fp from handler and discard handler state.
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 1 * kPointerSize);
   pop(ebp);
   pop(edx);  // State.
 
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   ret(0);
 }
 
@@ -1190,6 +1208,42 @@
 }
 
 
+void MacroAssembler::AllocateSlicedString(Register result,
+                                          Register scratch1,
+                                          Register scratch2,
+                                          Label* gc_required) {
+  // Allocate heap number in new space.
+  AllocateInNewSpace(SlicedString::kSize,
+                     result,
+                     scratch1,
+                     scratch2,
+                     gc_required,
+                     TAG_OBJECT);
+
+  // Set the map. The other fields are left uninitialized.
+  mov(FieldOperand(result, HeapObject::kMapOffset),
+      Immediate(isolate()->factory()->sliced_string_map()));
+}
+
+
+void MacroAssembler::AllocateAsciiSlicedString(Register result,
+                                               Register scratch1,
+                                               Register scratch2,
+                                               Label* gc_required) {
+  // Allocate heap number in new space.
+  AllocateInNewSpace(SlicedString::kSize,
+                     result,
+                     scratch1,
+                     scratch2,
+                     gc_required,
+                     TAG_OBJECT);
+
+  // Set the map. The other fields are left uninitialized.
+  mov(FieldOperand(result, HeapObject::kMapOffset),
+      Immediate(isolate()->factory()->sliced_ascii_string_map()));
+}
+
+
 // Copy memory, byte-by-byte, from source to destination.  Not optimized for
 // long or aligned copies.  The contents of scratch and length are destroyed.
 // Source and destination are incremented by length.
@@ -2148,7 +2202,7 @@
                                                          Register scratch2,
                                                          Label* failure) {
   // Check that both objects are not smis.
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   mov(scratch1, Operand(object1));
   and_(scratch1, Operand(object2));
   JumpIfSmi(scratch1, failure);
diff --git a/src/ia32/macro-assembler-ia32.h b/src/ia32/macro-assembler-ia32.h
index dac2273..de9361d 100644
--- a/src/ia32/macro-assembler-ia32.h
+++ b/src/ia32/macro-assembler-ia32.h
@@ -209,6 +209,9 @@
   void SafeSet(Register dst, const Immediate& x);
   void SafePush(const Immediate& x);
 
+  // Compare a register against a known root, e.g. undefined, null, true, ...
+  void CompareRoot(Register with, Heap::RootListIndex index);
+
   // Compare object type for heap object.
   // Incoming register is heap_object and outgoing register is map.
   void CmpObjectType(Register heap_object, InstanceType type, Register map);
@@ -272,8 +275,8 @@
 
   // Smi tagging support.
   void SmiTag(Register reg) {
-    ASSERT(kSmiTag == 0);
-    ASSERT(kSmiTagSize == 1);
+    STATIC_ASSERT(kSmiTag == 0);
+    STATIC_ASSERT(kSmiTagSize == 1);
     add(reg, Operand(reg));
   }
   void SmiUntag(Register reg) {
@@ -282,9 +285,9 @@
 
   // Modifies the register even if it does not contain a Smi!
   void SmiUntag(Register reg, Label* is_smi) {
-    ASSERT(kSmiTagSize == 1);
+    STATIC_ASSERT(kSmiTagSize == 1);
     sar(reg, kSmiTagSize);
-    ASSERT(kSmiTag == 0);
+    STATIC_ASSERT(kSmiTag == 0);
     j(not_carry, is_smi);
   }
 
@@ -443,6 +446,17 @@
                                Register scratch2,
                                Label* gc_required);
 
+  // Allocate a raw sliced string object. Only the map field of the result is
+  // initialized.
+  void AllocateSlicedString(Register result,
+                            Register scratch1,
+                            Register scratch2,
+                            Label* gc_required);
+  void AllocateAsciiSlicedString(Register result,
+                                 Register scratch1,
+                                 Register scratch2,
+                                 Label* gc_required);
+
   // Copy memory, byte-by-byte, from source to destination.  Not optimized for
   // long or aligned copies.
   // The contents of index and scratch are destroyed.
diff --git a/src/ia32/regexp-macro-assembler-ia32.cc b/src/ia32/regexp-macro-assembler-ia32.cc
index 8db2e9b..d175d9e 100644
--- a/src/ia32/regexp-macro-assembler-ia32.cc
+++ b/src/ia32/regexp-macro-assembler-ia32.cc
@@ -1065,12 +1065,13 @@
   }
 
   // Prepare for possible GC.
-  HandleScope handles;
+  HandleScope handles(isolate);
   Handle<Code> code_handle(re_code);
 
   Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
+
   // Current string.
-  bool is_ascii = subject->IsAsciiRepresentation();
+  bool is_ascii = subject->IsAsciiRepresentationUnderneath();
 
   ASSERT(re_code->instruction_start() <= *return_address);
   ASSERT(*return_address <=
@@ -1079,7 +1080,7 @@
   MaybeObject* result = Execution::HandleStackGuardInterrupt();
 
   if (*code_handle != re_code) {  // Return address no longer valid
-    int delta = *code_handle - re_code;
+    int delta = code_handle->address() - re_code->address();
     // Overwrite the return address on the stack.
     *return_address += delta;
   }
@@ -1088,8 +1089,20 @@
     return EXCEPTION;
   }
 
+  Handle<String> subject_tmp = subject;
+  int slice_offset = 0;
+
+  // Extract the underlying string and the slice offset.
+  if (StringShape(*subject_tmp).IsCons()) {
+    subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
+  } else if (StringShape(*subject_tmp).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(*subject_tmp);
+    subject_tmp = Handle<String>(slice->parent());
+    slice_offset = slice->offset();
+  }
+
   // String might have changed.
-  if (subject->IsAsciiRepresentation() != is_ascii) {
+  if (subject_tmp->IsAsciiRepresentation() != is_ascii) {
     // If we changed between an ASCII and an UC16 string, the specialized
     // code cannot be used, and we need to restart regexp matching from
     // scratch (including, potentially, compiling a new version of the code).
@@ -1100,8 +1113,8 @@
   // be a sequential or external string with the same content.
   // Update the start and end pointers in the stack frame to the current
   // location (whether it has actually moved or not).
-  ASSERT(StringShape(*subject).IsSequential() ||
-      StringShape(*subject).IsExternal());
+  ASSERT(StringShape(*subject_tmp).IsSequential() ||
+      StringShape(*subject_tmp).IsExternal());
 
   // The original start address of the characters to match.
   const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);
@@ -1109,13 +1122,14 @@
   // Find the current start address of the same character at the current string
   // position.
   int start_index = frame_entry<int>(re_frame, kStartIndex);
-  const byte* new_address = StringCharacterPosition(*subject, start_index);
+  const byte* new_address = StringCharacterPosition(*subject_tmp,
+                                                    start_index + slice_offset);
 
   if (start_address != new_address) {
     // If there is a difference, update the object pointer and start and end
     // addresses in the RegExp stack frame to match the new value.
     const byte* end_address = frame_entry<const byte* >(re_frame, kInputEnd);
-    int byte_length = end_address - start_address;
+    int byte_length = static_cast<int>(end_address - start_address);
     frame_entry<const String*>(re_frame, kInputString) = *subject;
     frame_entry<const byte*>(re_frame, kInputStart) = new_address;
     frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
diff --git a/src/ia32/stub-cache-ia32.cc b/src/ia32/stub-cache-ia32.cc
index 9a690d7..621a9bb 100644
--- a/src/ia32/stub-cache-ia32.cc
+++ b/src/ia32/stub-cache-ia32.cc
@@ -273,7 +273,7 @@
   // Check that the object is a string.
   __ mov(scratch, FieldOperand(receiver, HeapObject::kMapOffset));
   __ movzx_b(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
-  ASSERT(kNotStringTag != 0);
+  STATIC_ASSERT(kNotStringTag != 0);
   __ test(scratch, Immediate(kNotStringTag));
   __ j(not_zero, non_string_object);
 }
@@ -3400,37 +3400,37 @@
   __ JumpIfNotSmi(eax, &miss_force_generic);
 
   // Check that the index is in range.
-  __ mov(ecx, eax);
-  __ SmiUntag(ecx);  // Untag the index.
   __ mov(ebx, FieldOperand(edx, JSObject::kElementsOffset));
-  __ cmp(ecx, FieldOperand(ebx, ExternalArray::kLengthOffset));
+  __ cmp(eax, FieldOperand(ebx, ExternalArray::kLengthOffset));
   // Unsigned comparison catches both negative and too-large values.
   __ j(above_equal, &miss_force_generic);
   __ mov(ebx, FieldOperand(ebx, ExternalArray::kExternalPointerOffset));
   // ebx: base pointer of external storage
   switch (elements_kind) {
     case JSObject::EXTERNAL_BYTE_ELEMENTS:
-      __ movsx_b(eax, Operand(ebx, ecx, times_1, 0));
+      __ SmiUntag(eax);  // Untag the index.
+      __ movsx_b(eax, Operand(ebx, eax, times_1, 0));
       break;
     case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
     case JSObject::EXTERNAL_PIXEL_ELEMENTS:
-      __ movzx_b(eax, Operand(ebx, ecx, times_1, 0));
+      __ SmiUntag(eax);  // Untag the index.
+      __ movzx_b(eax, Operand(ebx, eax, times_1, 0));
       break;
     case JSObject::EXTERNAL_SHORT_ELEMENTS:
-      __ movsx_w(eax, Operand(ebx, ecx, times_2, 0));
+      __ movsx_w(eax, Operand(ebx, eax, times_1, 0));
       break;
     case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-      __ movzx_w(eax, Operand(ebx, ecx, times_2, 0));
+      __ movzx_w(eax, Operand(ebx, eax, times_1, 0));
       break;
     case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
     case JSObject::EXTERNAL_INT_ELEMENTS:
-      __ mov(ecx, Operand(ebx, ecx, times_4, 0));
+      __ mov(ecx, Operand(ebx, eax, times_2, 0));
       break;
     case JSObject::EXTERNAL_FLOAT_ELEMENTS:
-      __ fld_s(Operand(ebx, ecx, times_4, 0));
+      __ fld_s(Operand(ebx, eax, times_2, 0));
       break;
     case JSObject::EXTERNAL_DOUBLE_ELEMENTS:
-      __ fld_d(Operand(ebx, ecx, times_8, 0));
+      __ fld_d(Operand(ebx, eax, times_4, 0));
       break;
     default:
       UNREACHABLE();
@@ -3556,9 +3556,7 @@
 
   // Check that the index is in range.
   __ mov(edi, FieldOperand(edx, JSObject::kElementsOffset));
-  __ mov(ebx, ecx);
-  __ SmiUntag(ebx);
-  __ cmp(ebx, FieldOperand(edi, ExternalArray::kLengthOffset));
+  __ cmp(ecx, FieldOperand(edi, ExternalArray::kLengthOffset));
   // Unsigned comparison catches both negative and too-large values.
   __ j(above_equal, &slow);
 
@@ -3568,7 +3566,6 @@
   // edx: receiver
   // ecx: key
   // edi: elements array
-  // ebx: untagged index
   if (elements_kind == JSObject::EXTERNAL_PIXEL_ELEMENTS) {
     __ JumpIfNotSmi(eax, &slow);
   } else {
@@ -3576,44 +3573,39 @@
   }
 
   // smi case
-  __ mov(ecx, eax);  // Preserve the value in eax.  Key is no longer needed.
-  __ SmiUntag(ecx);
+  __ mov(ebx, eax);  // Preserve the value in eax as the return value.
+  __ SmiUntag(ebx);
   __ mov(edi, FieldOperand(edi, ExternalArray::kExternalPointerOffset));
-  // ecx: base pointer of external storage
+  // edi: base pointer of external storage
   switch (elements_kind) {
     case JSObject::EXTERNAL_PIXEL_ELEMENTS:
-      {  // Clamp the value to [0..255].
-        Label done;
-        __ test(ecx, Immediate(0xFFFFFF00));
-        __ j(zero, &done, Label::kNear);
-        __ setcc(negative, ecx);  // 1 if negative, 0 if positive.
-        __ dec_b(ecx);  // 0 if negative, 255 if positive.
-        __ bind(&done);
-      }
-      __ mov_b(Operand(edi, ebx, times_1, 0), ecx);
+      __ ClampUint8(ebx);
+      __ SmiUntag(ecx);
+      __ mov_b(Operand(edi, ecx, times_1, 0), ebx);
       break;
     case JSObject::EXTERNAL_BYTE_ELEMENTS:
     case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-      __ mov_b(Operand(edi, ebx, times_1, 0), ecx);
+      __ SmiUntag(ecx);
+      __ mov_b(Operand(edi, ecx, times_1, 0), ebx);
       break;
     case JSObject::EXTERNAL_SHORT_ELEMENTS:
     case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-      __ mov_w(Operand(edi, ebx, times_2, 0), ecx);
+      __ mov_w(Operand(edi, ecx, times_1, 0), ebx);
       break;
     case JSObject::EXTERNAL_INT_ELEMENTS:
     case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
-      __ mov(Operand(edi, ebx, times_4, 0), ecx);
+      __ mov(Operand(edi, ecx, times_2, 0), ebx);
       break;
     case JSObject::EXTERNAL_FLOAT_ELEMENTS:
     case JSObject::EXTERNAL_DOUBLE_ELEMENTS:
       // Need to perform int-to-float conversion.
-      __ push(ecx);
+      __ push(ebx);
       __ fild_s(Operand(esp, 0));
-      __ pop(ecx);
+      __ pop(ebx);
       if (elements_kind == JSObject::EXTERNAL_FLOAT_ELEMENTS) {
-        __ fstp_s(Operand(edi, ebx, times_4, 0));
+        __ fstp_s(Operand(edi, ecx, times_2, 0));
       } else {  // elements_kind == JSObject::EXTERNAL_DOUBLE_ELEMENTS.
-        __ fstp_d(Operand(edi, ebx, times_8, 0));
+        __ fstp_d(Operand(edi, ecx, times_4, 0));
       }
       break;
     default:
@@ -3629,7 +3621,6 @@
     // edx: receiver
     // ecx: key
     // edi: elements array
-    // ebx: untagged index
     __ cmp(FieldOperand(eax, HeapObject::kMapOffset),
            Immediate(masm->isolate()->factory()->heap_number_map()));
     __ j(not_equal, &slow);
@@ -3638,15 +3629,14 @@
     // +/-Infinity into integer arrays basically undefined. For more
     // reproducible behavior, convert these to zero.
     __ mov(edi, FieldOperand(edi, ExternalArray::kExternalPointerOffset));
-    // ebx: untagged index
     // edi: base pointer of external storage
     if (elements_kind == JSObject::EXTERNAL_FLOAT_ELEMENTS) {
       __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
-      __ fstp_s(Operand(edi, ebx, times_4, 0));
+      __ fstp_s(Operand(edi, ecx, times_2, 0));
       __ ret(0);
     } else if (elements_kind == JSObject::EXTERNAL_DOUBLE_ELEMENTS) {
       __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
-      __ fstp_d(Operand(edi, ebx, times_8, 0));
+      __ fstp_d(Operand(edi, ecx, times_4, 0));
       __ ret(0);
     } else {
       // Perform float-to-int conversion with truncation (round-to-zero)
@@ -3661,27 +3651,20 @@
             elements_kind != JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS) {
           ASSERT(CpuFeatures::IsSupported(SSE2));
           CpuFeatures::Scope scope(SSE2);
-          __ cvttsd2si(ecx, FieldOperand(eax, HeapNumber::kValueOffset));
+          __ cvttsd2si(ebx, FieldOperand(eax, HeapNumber::kValueOffset));
           // ecx: untagged integer value
           switch (elements_kind) {
             case JSObject::EXTERNAL_PIXEL_ELEMENTS:
-              {  // Clamp the value to [0..255].
-                Label done;
-                __ test(ecx, Immediate(0xFFFFFF00));
-                __ j(zero, &done, Label::kNear);
-                __ setcc(negative, ecx);  // 1 if negative, 0 if positive.
-                __ dec_b(ecx);  // 0 if negative, 255 if positive.
-                __ bind(&done);
-              }
-              __ mov_b(Operand(edi, ebx, times_1, 0), ecx);
-              break;
+              __ ClampUint8(ebx);
+              // Fall through.
             case JSObject::EXTERNAL_BYTE_ELEMENTS:
             case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-              __ mov_b(Operand(edi, ebx, times_1, 0), ecx);
+              __ SmiUntag(ecx);
+              __ mov_b(Operand(edi, ecx, times_1, 0), ebx);
               break;
             case JSObject::EXTERNAL_SHORT_ELEMENTS:
             case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-              __ mov_w(Operand(edi, ebx, times_2, 0), ecx);
+              __ mov_w(Operand(edi, ecx, times_1, 0), ebx);
               break;
             default:
               UNREACHABLE();
@@ -3698,7 +3681,7 @@
             __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
             __ sub(Operand(esp), Immediate(2 * kPointerSize));
             __ fisttp_d(Operand(esp, 0));
-            __ pop(ecx);
+            __ pop(ebx);
             __ add(Operand(esp), Immediate(kPointerSize));
           } else {
             ASSERT(CpuFeatures::IsSupported(SSE2));
@@ -3709,15 +3692,15 @@
             // Note: we could do better for signed int arrays.
             __ movd(xmm0, FieldOperand(eax, HeapNumber::kValueOffset));
             // We will need the key if we have to make the slow runtime call.
-            __ push(ecx);
-            __ LoadPowerOf2(xmm1, ecx, 31);
-            __ pop(ecx);
+            __ push(ebx);
+            __ LoadPowerOf2(xmm1, ebx, 31);
+            __ pop(ebx);
             __ ucomisd(xmm1, xmm0);
             __ j(above_equal, &slow);
-            __ cvttsd2si(ecx, Operand(xmm0));
+            __ cvttsd2si(ebx, Operand(xmm0));
           }
-          // ecx: untagged integer value
-          __ mov(Operand(edi, ebx, times_4, 0), ecx);
+          // ebx: untagged integer value
+          __ mov(Operand(edi, ecx, times_2, 0), ebx);
         }
         __ ret(0);  // Return original value.
       }
@@ -3981,10 +3964,12 @@
 
   __ bind(&smi_value);
   // Value is a smi. convert to a double and store.
-  __ SmiUntag(eax);
-  __ push(eax);
+  // Preserve original value.
+  __ mov(edx, eax);
+  __ SmiUntag(edx);
+  __ push(edx);
   __ fild_s(Operand(esp, 0));
-  __ pop(eax);
+  __ pop(edx);
   __ fstp_d(FieldOperand(edi, ecx, times_4, FixedDoubleArray::kHeaderSize));
   __ ret(0);
 
diff --git a/src/ic.cc b/src/ic.cc
index f70f75a..0d0b935 100644
--- a/src/ic.cc
+++ b/src/ic.cc
@@ -88,7 +88,8 @@
       // function and the original code.
       JSFunction* function = JSFunction::cast(frame->function());
       function->PrintName();
-      int code_offset = address() - js_code->instruction_start();
+      int code_offset =
+          static_cast<int>(address() - js_code->instruction_start());
       PrintF("+%d", code_offset);
     } else {
       PrintF("<unknown>");
@@ -309,6 +310,7 @@
     case Code::UNARY_OP_IC:
     case Code::BINARY_OP_IC:
     case Code::COMPARE_IC:
+    case Code::TO_BOOLEAN_IC:
       // Clearing these is tricky and does not
       // make any performance difference.
       return;
@@ -842,14 +844,6 @@
 }
 
 
-#ifdef DEBUG
-#define TRACE_IC_NAMED(msg, name) \
-  if (FLAG_trace_ic) PrintF(msg, *(name)->ToCString())
-#else
-#define TRACE_IC_NAMED(msg, name)
-#endif
-
-
 MaybeObject* LoadIC::Load(State state,
                           Handle<Object> object,
                           Handle<String> name) {
@@ -2506,6 +2500,31 @@
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, ToBoolean_Patch) {
+  ASSERT(args.length() == 3);
+
+  HandleScope scope(isolate);
+  Handle<Object> object = args.at<Object>(0);
+  Register tos = Register::from_code(args.smi_at(1));
+  ToBooleanStub::Types old_types(args.smi_at(2));
+
+  ToBooleanStub::Types new_types(old_types);
+  bool to_boolean_value = new_types.Record(object);
+  old_types.TraceTransition(new_types);
+
+  ToBooleanStub stub(tos, new_types);
+  Handle<Code> code = stub.GetCode();
+  ToBooleanIC ic(isolate);
+  ic.patch(*code);
+  return Smi::FromInt(to_boolean_value ? 1 : 0);
+}
+
+
+void ToBooleanIC::patch(Code* code) {
+  set_target(code);
+}
+
+
 static const Address IC_utilities[] = {
 #define ADDR(name) FUNCTION_ADDR(name),
     IC_UTIL_LIST(ADDR)
diff --git a/src/ic.h b/src/ic.h
index 11c2e3a..2236ba3 100644
--- a/src/ic.h
+++ b/src/ic.h
@@ -59,7 +59,8 @@
   ICU(StoreInterceptorProperty)                       \
   ICU(UnaryOp_Patch)                                  \
   ICU(BinaryOp_Patch)                                 \
-  ICU(CompareIC_Miss)
+  ICU(CompareIC_Miss)                                 \
+  ICU(ToBoolean_Patch)
 //
 // IC is the base class for LoadIC, StoreIC, CallIC, KeyedLoadIC,
 // and KeyedStoreIC.
@@ -720,6 +721,15 @@
   Token::Value op_;
 };
 
+
+class ToBooleanIC: public IC {
+ public:
+  explicit ToBooleanIC(Isolate* isolate) : IC(NO_EXTRA_FRAME, isolate) { }
+
+  void patch(Code* code);
+};
+
+
 // Helper for BinaryOpIC and CompareIC.
 void PatchInlinedSmiCode(Address address);
 
diff --git a/src/interpreter-irregexp.cc b/src/interpreter-irregexp.cc
index 1c6c52c..796a447 100644
--- a/src/interpreter-irregexp.cc
+++ b/src/interpreter-irregexp.cc
@@ -1,4 +1,4 @@
-// Copyright 2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -635,8 +635,9 @@
   AssertNoAllocation a;
   const byte* code_base = code_array->GetDataStartAddress();
   uc16 previous_char = '\n';
-  if (subject->IsAsciiRepresentation()) {
-    Vector<const char> subject_vector = subject->ToAsciiVector();
+  String::FlatContent subject_content = subject->GetFlatContent();
+  if (subject_content.IsAscii()) {
+    Vector<const char> subject_vector = subject_content.ToAsciiVector();
     if (start_position != 0) previous_char = subject_vector[start_position - 1];
     return RawMatch(isolate,
                     code_base,
@@ -645,7 +646,8 @@
                     start_position,
                     previous_char);
   } else {
-    Vector<const uc16> subject_vector = subject->ToUC16Vector();
+    ASSERT(subject_content.IsTwoByte());
+    Vector<const uc16> subject_vector = subject_content.ToUC16Vector();
     if (start_position != 0) previous_char = subject_vector[start_position - 1];
     return RawMatch(isolate,
                     code_base,
diff --git a/src/isolate.cc b/src/isolate.cc
index 8a30e79..09cbc8a 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -76,6 +76,10 @@
 
 ThreadLocalTop::ThreadLocalTop() {
   InitializeInternal();
+  // This flag may be set using v8::V8::IgnoreOutOfMemoryException()
+  // before an isolate is initialized. The initialize methods below do
+  // not touch it to preserve its value.
+  ignore_out_of_memory_ = false;
 }
 
 
@@ -382,7 +386,6 @@
   if (Thread::GetThreadLocal(isolate_key_) == NULL) {
     Thread::SetThreadLocal(isolate_key_, default_isolate_);
   }
-  CHECK(default_isolate_->PreInit());
 }
 
 
@@ -654,6 +657,7 @@
     incomplete_message_ = &accumulator;
     PrintStack(&accumulator);
     accumulator.OutputToStdOut();
+    InitializeLoggingAndCounters();
     accumulator.Log();
     incomplete_message_ = NULL;
     stack_trace_nesting_level_ = 0;
@@ -1331,6 +1335,7 @@
   if (list_ == data) list_ = data->next_;
   if (data->next_ != NULL) data->next_->prev_ = data->prev_;
   if (data->prev_ != NULL) data->prev_->next_ = data->next_;
+  delete data;
 }
 
 
@@ -1375,11 +1380,15 @@
       bootstrapper_(NULL),
       runtime_profiler_(NULL),
       compilation_cache_(NULL),
-      counters_(new Counters()),
+      counters_(NULL),
       code_range_(NULL),
+      // Must be initialized early to allow v8::SetResourceConstraints calls.
       break_access_(OS::CreateMutex()),
-      logger_(new Logger()),
-      stats_table_(new StatsTable()),
+      debugger_initialized_(false),
+      // Must be initialized early to allow v8::Debug calls.
+      debugger_access_(OS::CreateMutex()),
+      logger_(NULL),
+      stats_table_(NULL),
       stub_cache_(NULL),
       deoptimizer_data_(NULL),
       capture_stack_trace_for_uncaught_exceptions_(false),
@@ -1510,7 +1519,7 @@
     logger_->TearDown();
 
     // The default isolate is re-initializable due to legacy API.
-    state_ = PREINITIALIZED;
+    state_ = UNINITIALIZED;
   }
 }
 
@@ -1525,6 +1534,12 @@
 Isolate::~Isolate() {
   TRACE_ISOLATE(destructor);
 
+  // Has to be called while counters_ are still alive.
+  zone_.DeleteKeptSegment();
+
+  delete[] assembler_spare_buffer_;
+  assembler_spare_buffer_ = NULL;
+
   delete unicode_cache_;
   unicode_cache_ = NULL;
 
@@ -1558,6 +1573,8 @@
   handle_scope_implementer_ = NULL;
   delete break_access_;
   break_access_ = NULL;
+  delete debugger_access_;
+  debugger_access_ = NULL;
 
   delete compilation_cache_;
   compilation_cache_ = NULL;
@@ -1583,6 +1600,9 @@
   delete global_handles_;
   global_handles_ = NULL;
 
+  delete external_reference_table_;
+  external_reference_table_ = NULL;
+
 #ifdef ENABLE_DEBUGGER_SUPPORT
   delete debugger_;
   debugger_ = NULL;
@@ -1592,58 +1612,6 @@
 }
 
 
-bool Isolate::PreInit() {
-  if (state_ != UNINITIALIZED) return true;
-
-  TRACE_ISOLATE(preinit);
-
-  ASSERT(Isolate::Current() == this);
-#ifdef ENABLE_DEBUGGER_SUPPORT
-  debug_ = new Debug(this);
-  debugger_ = new Debugger(this);
-#endif
-
-  memory_allocator_ = new MemoryAllocator();
-  memory_allocator_->isolate_ = this;
-  code_range_ = new CodeRange();
-  code_range_->isolate_ = this;
-
-  // Safe after setting Heap::isolate_, initializing StackGuard and
-  // ensuring that Isolate::Current() == this.
-  heap_.SetStackLimits();
-
-#ifdef DEBUG
-  DisallowAllocationFailure disallow_allocation_failure;
-#endif
-
-#define C(name) isolate_addresses_[Isolate::k_##name] =                        \
-    reinterpret_cast<Address>(name());
-  ISOLATE_ADDRESS_LIST(C)
-#undef C
-
-  string_tracker_ = new StringTracker();
-  string_tracker_->isolate_ = this;
-  compilation_cache_ = new CompilationCache(this);
-  transcendental_cache_ = new TranscendentalCache();
-  keyed_lookup_cache_ = new KeyedLookupCache();
-  context_slot_cache_ = new ContextSlotCache();
-  descriptor_lookup_cache_ = new DescriptorLookupCache();
-  unicode_cache_ = new UnicodeCache();
-  pc_to_code_cache_ = new PcToCodeCache(this);
-  write_input_buffer_ = new StringInputBuffer();
-  global_handles_ = new GlobalHandles(this);
-  bootstrapper_ = new Bootstrapper();
-  handle_scope_implementer_ = new HandleScopeImplementer(this);
-  stub_cache_ = new StubCache(this);
-  ast_sentinels_ = new AstSentinels();
-  regexp_stack_ = new RegExpStack();
-  regexp_stack_->isolate_ = this;
-
-  state_ = PREINITIALIZED;
-  return true;
-}
-
-
 void Isolate::InitializeThreadLocal() {
   thread_local_top_.isolate_ = this;
   thread_local_top_.Initialize();
@@ -1680,19 +1648,71 @@
 }
 
 
+void Isolate::InitializeLoggingAndCounters() {
+  if (logger_ == NULL) {
+    logger_ = new Logger;
+  }
+  if (counters_ == NULL) {
+    counters_ = new Counters;
+  }
+}
+
+
+void Isolate::InitializeDebugger() {
+#ifdef ENABLE_DEBUGGER_SUPPORT
+  ScopedLock lock(debugger_access_);
+  if (NoBarrier_Load(&debugger_initialized_)) return;
+  InitializeLoggingAndCounters();
+  debug_ = new Debug(this);
+  debugger_ = new Debugger(this);
+  Release_Store(&debugger_initialized_, true);
+#endif
+}
+
+
 bool Isolate::Init(Deserializer* des) {
   ASSERT(state_ != INITIALIZED);
-
+  ASSERT(Isolate::Current() == this);
   TRACE_ISOLATE(init);
 
-  bool create_heap_objects = des == NULL;
-
 #ifdef DEBUG
   // The initialization process does not handle memory exhaustion.
   DisallowAllocationFailure disallow_allocation_failure;
 #endif
 
-  if (state_ == UNINITIALIZED && !PreInit()) return false;
+  InitializeLoggingAndCounters();
+
+  InitializeDebugger();
+
+  memory_allocator_ = new MemoryAllocator(this);
+  code_range_ = new CodeRange(this);
+
+  // Safe after setting Heap::isolate_, initializing StackGuard and
+  // ensuring that Isolate::Current() == this.
+  heap_.SetStackLimits();
+
+#define C(name) isolate_addresses_[Isolate::k_##name] =                        \
+    reinterpret_cast<Address>(name());
+  ISOLATE_ADDRESS_LIST(C)
+#undef C
+
+  string_tracker_ = new StringTracker();
+  string_tracker_->isolate_ = this;
+  compilation_cache_ = new CompilationCache(this);
+  transcendental_cache_ = new TranscendentalCache();
+  keyed_lookup_cache_ = new KeyedLookupCache();
+  context_slot_cache_ = new ContextSlotCache();
+  descriptor_lookup_cache_ = new DescriptorLookupCache();
+  unicode_cache_ = new UnicodeCache();
+  pc_to_code_cache_ = new PcToCodeCache(this);
+  write_input_buffer_ = new StringInputBuffer();
+  global_handles_ = new GlobalHandles(this);
+  bootstrapper_ = new Bootstrapper();
+  handle_scope_implementer_ = new HandleScopeImplementer(this);
+  stub_cache_ = new StubCache(this);
+  ast_sentinels_ = new AstSentinels();
+  regexp_stack_ = new RegExpStack();
+  regexp_stack_->isolate_ = this;
 
   // Enable logging before setting up the heap
   logger_->Setup();
@@ -1715,7 +1735,8 @@
     stack_guard_.InitThread(lock);
   }
 
-  // Setup the object heap
+  // Setup the object heap.
+  const bool create_heap_objects = (des == NULL);
   ASSERT(!heap_.HasBeenSetup());
   if (!heap_.Setup(create_heap_objects)) {
     V8::SetFatalError();
@@ -1775,6 +1796,16 @@
 }
 
 
+// Initialized lazily to allow early
+// v8::V8::SetAddHistogramSampleFunction calls.
+StatsTable* Isolate::stats_table() {
+  if (stats_table_ == NULL) {
+    stats_table_ = new StatsTable;
+  }
+  return stats_table_;
+}
+
+
 void Isolate::Enter() {
   Isolate* current_isolate = NULL;
   PerIsolateThreadData* current_data = CurrentPerIsolateThreadData();
@@ -1814,8 +1845,6 @@
 
   SetIsolateThreadLocals(this, data);
 
-  CHECK(PreInit());
-
   // In case it's the first time some thread enters the isolate.
   set_thread_id(data->thread_id());
 }
diff --git a/src/isolate.h b/src/isolate.h
index f2281aa..5bb504d 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -256,6 +256,9 @@
   // Call back function to report unsafe JS accesses.
   v8::FailedAccessCheckCallback failed_access_check_callback_;
 
+  // Whether out of memory exceptions should be ignored.
+  bool ignore_out_of_memory_;
+
  private:
   void InitializeInternal();
 
@@ -446,6 +449,13 @@
     return reinterpret_cast<Isolate*>(Thread::GetThreadLocal(isolate_key_));
   }
 
+  // Usually called by Init(), but can be called early e.g. to allow
+  // testing components that require logging but not the whole
+  // isolate.
+  //
+  // Safe to call more than once.
+  void InitializeLoggingAndCounters();
+
   bool Init(Deserializer* des);
 
   bool IsInitialized() { return state_ == INITIALIZED; }
@@ -498,10 +508,12 @@
   // switched to non-legacy behavior).
   static void EnterDefaultIsolate();
 
-  // Debug.
   // Mutex for serializing access to break control structures.
   Mutex* break_access() { return break_access_; }
 
+  // Mutex for serializing access to debugger.
+  Mutex* debugger_access() { return debugger_access_; }
+
   Address get_address_from_id(AddressId id);
 
   // Access to top context (where the current function object was created).
@@ -661,6 +673,12 @@
   // Tells whether the current context has experienced an out of memory
   // exception.
   bool is_out_of_memory();
+  bool ignore_out_of_memory() {
+    return thread_local_top_.ignore_out_of_memory_;
+  }
+  void set_ignore_out_of_memory(bool value) {
+    thread_local_top_.ignore_out_of_memory_ = value;
+  }
 
   void PrintCurrentStackTrace(FILE* out);
   void PrintStackTrace(FILE* out, char* thread_data);
@@ -769,14 +787,24 @@
 #undef GLOBAL_CONTEXT_FIELD_ACCESSOR
 
   Bootstrapper* bootstrapper() { return bootstrapper_; }
-  Counters* counters() { return counters_; }
+  Counters* counters() {
+    // Call InitializeLoggingAndCounters() if logging is needed before
+    // the isolate is fully initialized.
+    ASSERT(counters_ != NULL);
+    return counters_;
+  }
   CodeRange* code_range() { return code_range_; }
   RuntimeProfiler* runtime_profiler() { return runtime_profiler_; }
   CompilationCache* compilation_cache() { return compilation_cache_; }
-  Logger* logger() { return logger_; }
+  Logger* logger() {
+    // Call InitializeLoggingAndCounters() if logging is needed before
+    // the isolate is fully initialized.
+    ASSERT(logger_ != NULL);
+    return logger_;
+  }
   StackGuard* stack_guard() { return &stack_guard_; }
   Heap* heap() { return &heap_; }
-  StatsTable* stats_table() { return stats_table_; }
+  StatsTable* stats_table();
   StubCache* stub_cache() { return stub_cache_; }
   DeoptimizerData* deoptimizer_data() { return deoptimizer_data_; }
   ThreadLocalTop* thread_local_top() { return &thread_local_top_; }
@@ -877,8 +905,14 @@
   void PreallocatedStorageInit(size_t size);
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
-  Debugger* debugger() { return debugger_; }
-  Debug* debug() { return debug_; }
+  Debugger* debugger() {
+    if (!NoBarrier_Load(&debugger_initialized_)) InitializeDebugger();
+    return debugger_;
+  }
+  Debug* debug() {
+    if (!NoBarrier_Load(&debugger_initialized_)) InitializeDebugger();
+    return debug_;
+  }
 #endif
 
   inline bool DebuggerHasBreakPoints();
@@ -1010,8 +1044,6 @@
   static Isolate* default_isolate_;
   static ThreadDataTable* thread_data_table_;
 
-  bool PreInit();
-
   void Deinit();
 
   static void SetIsolateThreadLocals(Isolate* isolate,
@@ -1019,7 +1051,6 @@
 
   enum State {
     UNINITIALIZED,    // Some components may not have been allocated.
-    PREINITIALIZED,   // Components have been allocated but not initialized.
     INITIALIZED       // All components are fully initialized.
   };
 
@@ -1063,6 +1094,8 @@
 
   void PropagatePendingExceptionToExternalTryCatch();
 
+  void InitializeDebugger();
+
   int stack_trace_nesting_level_;
   StringStream* incomplete_message_;
   // The preallocated memory thread singleton.
@@ -1076,6 +1109,8 @@
   Counters* counters_;
   CodeRange* code_range_;
   Mutex* break_access_;
+  Atomic32 debugger_initialized_;
+  Mutex* debugger_access_;
   Heap heap_;
   Logger* logger_;
   StackGuard stack_guard_;
@@ -1165,6 +1200,7 @@
   friend class Simulator;
   friend class StackGuard;
   friend class ThreadId;
+  friend class TestMemoryAllocatorScope;
   friend class v8::Isolate;
   friend class v8::Locker;
   friend class v8::Unlocker;
diff --git a/src/json-parser.h b/src/json-parser.h
index 0c01461..68eab65 100644
--- a/src/json-parser.h
+++ b/src/json-parser.h
@@ -166,7 +166,8 @@
 template <bool seq_ascii>
 Handle<Object> JsonParser<seq_ascii>::ParseJson(Handle<String> source) {
   isolate_ = source->map()->isolate();
-  source_ = Handle<String>(source->TryFlattenGetString());
+  FlattenString(source);
+  source_ = source;
   source_length_ = source_->length();
 
   // Optimized fast case where we only have ASCII characters.
diff --git a/src/json.js b/src/json.js
index 6c984a1..8fd410f 100644
--- a/src/json.js
+++ b/src/json.js
@@ -237,7 +237,7 @@
     }
   }
   stack.pop();
-  builder.push("]"); 
+  builder.push("]");
 }
 
 
diff --git a/src/jsregexp.cc b/src/jsregexp.cc
index bc47df8..4ca83a4 100644
--- a/src/jsregexp.cc
+++ b/src/jsregexp.cc
@@ -212,19 +212,7 @@
   RegExpImpl::SetCapture(array, 1, to);
 }
 
-  /* template <typename SubjectChar>, typename PatternChar>
-static int ReStringMatch(Vector<const SubjectChar> sub_vector,
-                         Vector<const PatternChar> pat_vector,
-                         int start_index) {
 
-  int pattern_length = pat_vector.length();
-  if (pattern_length == 0) return start_index;
-
-  int subject_length = sub_vector.length();
-  if (start_index + pattern_length > subject_length) return -1;
-  return SearchString(sub_vector, pat_vector, start_index);
-}
-  */
 Handle<Object> RegExpImpl::AtomExec(Handle<JSRegExp> re,
                                     Handle<String> subject,
                                     int index,
@@ -236,38 +224,41 @@
 
   if (!subject->IsFlat()) FlattenString(subject);
   AssertNoAllocation no_heap_allocation;  // ensure vectors stay valid
-  // Extract flattened substrings of cons strings before determining asciiness.
-  String* seq_sub = *subject;
-  if (seq_sub->IsConsString()) seq_sub = ConsString::cast(seq_sub)->first();
 
   String* needle = String::cast(re->DataAt(JSRegExp::kAtomPatternIndex));
   int needle_len = needle->length();
+  ASSERT(needle->IsFlat());
 
   if (needle_len != 0) {
-    if (index + needle_len > subject->length())
-        return isolate->factory()->null_value();
+    if (index + needle_len > subject->length()) {
+      return isolate->factory()->null_value();
+    }
 
+    String::FlatContent needle_content = needle->GetFlatContent();
+    String::FlatContent subject_content = subject->GetFlatContent();
+    ASSERT(needle_content.IsFlat());
+    ASSERT(subject_content.IsFlat());
     // dispatch on type of strings
-    index = (needle->IsAsciiRepresentation()
-             ? (seq_sub->IsAsciiRepresentation()
+    index = (needle_content.IsAscii()
+             ? (subject_content.IsAscii()
                 ? SearchString(isolate,
-                               seq_sub->ToAsciiVector(),
-                               needle->ToAsciiVector(),
+                               subject_content.ToAsciiVector(),
+                               needle_content.ToAsciiVector(),
                                index)
                 : SearchString(isolate,
-                               seq_sub->ToUC16Vector(),
-                               needle->ToAsciiVector(),
+                               subject_content.ToUC16Vector(),
+                               needle_content.ToAsciiVector(),
                                index))
-             : (seq_sub->IsAsciiRepresentation()
+             : (subject_content.IsAscii()
                 ? SearchString(isolate,
-                               seq_sub->ToAsciiVector(),
-                               needle->ToUC16Vector(),
+                               subject_content.ToAsciiVector(),
+                               needle_content.ToUC16Vector(),
                                index)
                 : SearchString(isolate,
-                               seq_sub->ToUC16Vector(),
-                               needle->ToUC16Vector(),
+                               subject_content.ToUC16Vector(),
+                               needle_content.ToUC16Vector(),
                                index)));
-    if (index == -1) return FACTORY->null_value();
+    if (index == -1) return isolate->factory()->null_value();
   }
   ASSERT(last_match_info->HasFastElements());
 
@@ -355,10 +346,7 @@
   JSRegExp::Flags flags = re->GetFlags();
 
   Handle<String> pattern(re->Pattern());
-  if (!pattern->IsFlat()) {
-    FlattenString(pattern);
-  }
-
+  if (!pattern->IsFlat()) FlattenString(pattern);
   RegExpCompileData compile_data;
   FlatStringReader reader(isolate, pattern);
   if (!RegExpParser::ParseRegExp(&reader, flags.is_multiline(),
@@ -442,22 +430,12 @@
 
 int RegExpImpl::IrregexpPrepare(Handle<JSRegExp> regexp,
                                 Handle<String> subject) {
-  if (!subject->IsFlat()) {
-    FlattenString(subject);
-  }
+  if (!subject->IsFlat()) FlattenString(subject);
+
   // Check the asciiness of the underlying storage.
-  bool is_ascii;
-  {
-    AssertNoAllocation no_gc;
-    String* sequential_string = *subject;
-    if (subject->IsConsString()) {
-      sequential_string = ConsString::cast(*subject)->first();
-    }
-    is_ascii = sequential_string->IsAsciiRepresentation();
-  }
-  if (!EnsureCompiledIrregexp(regexp, is_ascii)) {
-    return -1;
-  }
+  bool is_ascii = subject->IsAsciiRepresentationUnderneath();
+  if (!EnsureCompiledIrregexp(regexp, is_ascii)) return -1;
+
 #ifdef V8_INTERPRETED_REGEXP
   // Byte-code regexp needs space allocated for all its registers.
   return IrregexpNumberOfRegisters(FixedArray::cast(regexp->data()));
@@ -482,15 +460,11 @@
   ASSERT(index <= subject->length());
   ASSERT(subject->IsFlat());
 
-  // A flat ASCII string might have a two-byte first part.
-  if (subject->IsConsString()) {
-    subject = Handle<String>(ConsString::cast(*subject)->first(), isolate);
-  }
+  bool is_ascii = subject->IsAsciiRepresentationUnderneath();
 
 #ifndef V8_INTERPRETED_REGEXP
   ASSERT(output.length() >= (IrregexpNumberOfCaptures(*irregexp) + 1) * 2);
   do {
-    bool is_ascii = subject->IsAsciiRepresentation();
     EnsureCompiledIrregexp(regexp, is_ascii);
     Handle<Code> code(IrregexpNativeCode(*irregexp, is_ascii), isolate);
     NativeRegExpMacroAssembler::Result res =
@@ -518,13 +492,13 @@
     // being internal and external, and even between being ASCII and UC16,
     // but the characters are always the same).
     IrregexpPrepare(regexp, subject);
+    is_ascii = subject->IsAsciiRepresentationUnderneath();
   } while (true);
   UNREACHABLE();
   return RE_EXCEPTION;
 #else  // V8_INTERPRETED_REGEXP
 
   ASSERT(output.length() >= IrregexpNumberOfRegisters(*irregexp));
-  bool is_ascii = subject->IsAsciiRepresentation();
   // We must have done EnsureCompiledIrregexp, so we can get the number of
   // registers.
   int* register_vector = output.start();
diff --git a/src/liveobjectlist.cc b/src/liveobjectlist.cc
index e382a06..451a28a 100644
--- a/src/liveobjectlist.cc
+++ b/src/liveobjectlist.cc
@@ -36,11 +36,12 @@
 #include "global-handles.h"
 #include "heap.h"
 #include "inspector.h"
+#include "isolate.h"
 #include "list-inl.h"
 #include "liveobjectlist-inl.h"
 #include "string-stream.h"
-#include "top.h"
 #include "v8utils.h"
+#include "v8conversions.h"
 
 namespace v8 {
 namespace internal {
@@ -109,7 +110,7 @@
   \
   v(Context, "meta: Context") \
   v(ByteArray, "meta: ByteArray") \
-  v(PixelArray, "meta: PixelArray") \
+  v(ExternalPixelArray, "meta: PixelArray") \
   v(ExternalArray, "meta: ExternalArray") \
   v(FixedArray, "meta: FixedArray") \
   v(String, "String") \
@@ -211,8 +212,9 @@
 
 
 static bool InSpace(AllocationSpace space, HeapObject *heap_obj) {
+  Heap* heap = ISOLATE->heap();
   if (space != LO_SPACE) {
-    return Heap::InSpace(heap_obj, space);
+    return heap->InSpace(heap_obj, space);
   }
 
   // This is an optimization to speed up the check for an object in the LO
@@ -224,11 +226,11 @@
   int first_space = static_cast<int>(FIRST_SPACE);
   int last_space = static_cast<int>(LO_SPACE);
   for (int sp = first_space; sp < last_space; sp++) {
-    if (Heap::InSpace(heap_obj, static_cast<AllocationSpace>(sp))) {
+    if (heap->InSpace(heap_obj, static_cast<AllocationSpace>(sp))) {
       return false;
     }
   }
-  SLOW_ASSERT(Heap::InSpace(heap_obj, LO_SPACE));
+  SLOW_ASSERT(heap->InSpace(heap_obj, LO_SPACE));
   return true;
 }
 
@@ -285,7 +287,7 @@
 
 
 void LolFilter::InitTypeFilter(Handle<JSObject> filter_obj) {
-  Handle<String> type_sym = Factory::LookupAsciiSymbol("type");
+  Handle<String> type_sym = FACTORY->LookupAsciiSymbol("type");
   MaybeObject* maybe_result = filter_obj->GetProperty(*type_sym);
   Object* type_obj;
   if (maybe_result->ToObject(&type_obj)) {
@@ -301,7 +303,7 @@
 
 
 void LolFilter::InitSpaceFilter(Handle<JSObject> filter_obj) {
-  Handle<String> space_sym = Factory::LookupAsciiSymbol("space");
+  Handle<String> space_sym = FACTORY->LookupAsciiSymbol("space");
   MaybeObject* maybe_result = filter_obj->GetProperty(*space_sym);
   Object* space_obj;
   if (maybe_result->ToObject(&space_obj)) {
@@ -317,7 +319,7 @@
 
 
 void LolFilter::InitPropertyFilter(Handle<JSObject> filter_obj) {
-  Handle<String> prop_sym = Factory::LookupAsciiSymbol("prop");
+  Handle<String> prop_sym = FACTORY->LookupAsciiSymbol("prop");
   MaybeObject* maybe_result = filter_obj->GetProperty(*prop_sym);
   Object* prop_obj;
   if (maybe_result->ToObject(&prop_obj)) {
@@ -571,7 +573,9 @@
                          Handle<JSObject> detail,
                          Handle<String> desc,
                          Handle<Object> error) {
-  detail = Factory::NewJSObject(Top::object_function());
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+  detail = factory->NewJSObject(isolate->object_function());
   if (detail->IsFailure()) {
     error = detail;
     return false;
@@ -586,7 +590,7 @@
     desc_str = buffer;
     size = obj->Size();
   }
-  desc = Factory::NewStringFromAscii(CStrVector(desc_str));
+  desc = factory->NewStringFromAscii(CStrVector(desc_str));
   if (desc->IsFailure()) {
     error = desc;
     return false;
@@ -663,10 +667,13 @@
     int index = 0;
     int count = 0;
 
+    Isolate* isolate = Isolate::Current();
+    Factory* factory = isolate->factory();
+
     // Prefetch some needed symbols.
-    Handle<String> id_sym = Factory::LookupAsciiSymbol("id");
-    Handle<String> desc_sym = Factory::LookupAsciiSymbol("desc");
-    Handle<String> size_sym = Factory::LookupAsciiSymbol("size");
+    Handle<String> id_sym = factory->LookupAsciiSymbol("id");
+    Handle<String> desc_sym = factory->LookupAsciiSymbol("desc");
+    Handle<String> size_sym = factory->LookupAsciiSymbol("size");
 
     // Fill the array with the lol object details.
     Handle<JSObject> detail;
@@ -1089,7 +1096,9 @@
 
 // Captures a current snapshot of all objects in the heap.
 MaybeObject* LiveObjectList::Capture() {
-  HandleScope scope;
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+  HandleScope scope(isolate);
 
   // Count the number of objects in the heap.
   int total_count = CountHeapObjects();
@@ -1139,11 +1148,11 @@
 #endif
   }
 
-  Handle<String> id_sym = Factory::LookupAsciiSymbol("id");
-  Handle<String> count_sym = Factory::LookupAsciiSymbol("count");
-  Handle<String> size_sym = Factory::LookupAsciiSymbol("size");
+  Handle<String> id_sym = factory->LookupAsciiSymbol("id");
+  Handle<String> count_sym = factory->LookupAsciiSymbol("count");
+  Handle<String> size_sym = factory->LookupAsciiSymbol("size");
 
-  Handle<JSObject> result = Factory::NewJSObject(Top::object_function());
+  Handle<JSObject> result = factory->NewJSObject(isolate->object_function());
   if (result->IsFailure()) return Object::cast(*result);
 
   { MaybeObject* maybe_result = result->SetProperty(*id_sym,
@@ -1259,7 +1268,10 @@
                                          int start,
                                          int dump_limit,
                                          LolFilter* filter) {
-  HandleScope scope;
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+
+  HandleScope scope(isolate);
 
   // Calculate the number of entries of the dump.
   int count = -1;
@@ -1277,7 +1289,7 @@
   }
 
   // Allocate an array to hold the result.
-  Handle<FixedArray> elements_arr = Factory::NewFixedArray(dump_limit);
+  Handle<FixedArray> elements_arr = factory->NewFixedArray(dump_limit);
   if (elements_arr->IsFailure()) return Object::cast(*elements_arr);
 
   // Fill in the dump.
@@ -1292,11 +1304,11 @@
   MaybeObject* maybe_result;
 
   // Allocate the result body.
-  Handle<JSObject> body = Factory::NewJSObject(Top::object_function());
+  Handle<JSObject> body = factory->NewJSObject(isolate->object_function());
   if (body->IsFailure()) return Object::cast(*body);
 
   // Set the updated body.count.
-  Handle<String> count_sym = Factory::LookupAsciiSymbol("count");
+  Handle<String> count_sym = factory->LookupAsciiSymbol("count");
   maybe_result = body->SetProperty(*count_sym,
                                    Smi::FromInt(count),
                                    NONE,
@@ -1305,7 +1317,7 @@
 
   // Set the updated body.size if appropriate.
   if (size >= 0) {
-    Handle<String> size_sym = Factory::LookupAsciiSymbol("size");
+    Handle<String> size_sym = factory->LookupAsciiSymbol("size");
     maybe_result = body->SetProperty(*size_sym,
                                      Smi::FromInt(size),
                                      NONE,
@@ -1314,7 +1326,7 @@
   }
 
   // Set body.first_index.
-  Handle<String> first_sym = Factory::LookupAsciiSymbol("first_index");
+  Handle<String> first_sym = factory->LookupAsciiSymbol("first_index");
   maybe_result = body->SetProperty(*first_sym,
                                    Smi::FromInt(start),
                                    NONE,
@@ -1322,12 +1334,12 @@
   if (maybe_result->IsFailure()) return maybe_result;
 
   // Allocate the JSArray of the elements.
-  Handle<JSObject> elements = Factory::NewJSObject(Top::array_function());
+  Handle<JSObject> elements = factory->NewJSObject(isolate->array_function());
   if (elements->IsFailure()) return Object::cast(*elements);
   Handle<JSArray>::cast(elements)->SetContent(*elements_arr);
 
   // Set body.elements.
-  Handle<String> elements_sym = Factory::LookupAsciiSymbol("elements");
+  Handle<String> elements_sym = factory->LookupAsciiSymbol("elements");
   maybe_result = body->SetProperty(*elements_sym,
                                    *elements,
                                    NONE,
@@ -1381,6 +1393,9 @@
   LiveObjectSummary summary(filter);
   writer->Write(&summary);
 
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+
   // The result body will look like this:
   // body: {
   //   count: <total_count>,
@@ -1398,21 +1413,21 @@
   // }
 
   // Prefetch some needed symbols.
-  Handle<String> desc_sym = Factory::LookupAsciiSymbol("desc");
-  Handle<String> count_sym = Factory::LookupAsciiSymbol("count");
-  Handle<String> size_sym = Factory::LookupAsciiSymbol("size");
-  Handle<String> summary_sym = Factory::LookupAsciiSymbol("summary");
+  Handle<String> desc_sym = factory->LookupAsciiSymbol("desc");
+  Handle<String> count_sym = factory->LookupAsciiSymbol("count");
+  Handle<String> size_sym = factory->LookupAsciiSymbol("size");
+  Handle<String> summary_sym = factory->LookupAsciiSymbol("summary");
 
   // Allocate the summary array.
   int entries_count = summary.GetNumberOfEntries();
   Handle<FixedArray> summary_arr =
-      Factory::NewFixedArray(entries_count);
+      factory->NewFixedArray(entries_count);
   if (summary_arr->IsFailure()) return Object::cast(*summary_arr);
 
   int idx = 0;
   for (int i = 0; i < LiveObjectSummary::kNumberOfEntries; i++) {
     // Allocate the summary record.
-    Handle<JSObject> detail = Factory::NewJSObject(Top::object_function());
+    Handle<JSObject> detail = factory->NewJSObject(isolate->object_function());
     if (detail->IsFailure()) return Object::cast(*detail);
 
     // Fill in the summary record.
@@ -1420,7 +1435,7 @@
     int count = summary.Count(type);
     if (count) {
       const char* desc_cstr = GetObjectTypeDesc(type);
-      Handle<String> desc = Factory::LookupAsciiSymbol(desc_cstr);
+      Handle<String> desc = factory->LookupAsciiSymbol(desc_cstr);
       int size = summary.Size(type);
 
       maybe_result = detail->SetProperty(*desc_sym,
@@ -1444,12 +1459,13 @@
   }
 
   // Wrap the summary fixed array in a JS array.
-  Handle<JSObject> summary_obj = Factory::NewJSObject(Top::array_function());
+  Handle<JSObject> summary_obj =
+    factory->NewJSObject(isolate->array_function());
   if (summary_obj->IsFailure()) return Object::cast(*summary_obj);
   Handle<JSArray>::cast(summary_obj)->SetContent(*summary_arr);
 
   // Create the body object.
-  Handle<JSObject> body = Factory::NewJSObject(Top::object_function());
+  Handle<JSObject> body = factory->NewJSObject(isolate->object_function());
   if (body->IsFailure()) return Object::cast(*body);
 
   // Fill out the body object.
@@ -1470,9 +1486,9 @@
   if (is_tracking_roots) {
     int found_root = summary.found_root();
     int found_weak_root = summary.found_weak_root();
-    Handle<String> root_sym = Factory::LookupAsciiSymbol("found_root");
+    Handle<String> root_sym = factory->LookupAsciiSymbol("found_root");
     Handle<String> weak_root_sym =
-        Factory::LookupAsciiSymbol("found_weak_root");
+        factory->LookupAsciiSymbol("found_weak_root");
     maybe_result = body->SetProperty(*root_sym,
                                      Smi::FromInt(found_root),
                                      NONE,
@@ -1499,7 +1515,10 @@
 // Note: only dumps the section starting at start_idx and only up to
 // dump_limit entries.
 MaybeObject* LiveObjectList::Info(int start_idx, int dump_limit) {
-  HandleScope scope;
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+
+  HandleScope scope(isolate);
   MaybeObject* maybe_result;
 
   int total_count = LiveObjectList::list_count();
@@ -1519,13 +1538,13 @@
   }
 
   // Allocate an array to hold the result.
-  Handle<FixedArray> list = Factory::NewFixedArray(dump_count);
+  Handle<FixedArray> list = factory->NewFixedArray(dump_count);
   if (list->IsFailure()) return Object::cast(*list);
 
   // Prefetch some needed symbols.
-  Handle<String> id_sym = Factory::LookupAsciiSymbol("id");
-  Handle<String> count_sym = Factory::LookupAsciiSymbol("count");
-  Handle<String> size_sym = Factory::LookupAsciiSymbol("size");
+  Handle<String> id_sym = factory->LookupAsciiSymbol("id");
+  Handle<String> count_sym = factory->LookupAsciiSymbol("count");
+  Handle<String> size_sym = factory->LookupAsciiSymbol("size");
 
   // Fill the array with the lol details.
   int idx = 0;
@@ -1543,7 +1562,8 @@
       int size;
       count = lol->GetTotalObjCountAndSize(&size);
 
-      Handle<JSObject> detail = Factory::NewJSObject(Top::object_function());
+      Handle<JSObject> detail =
+          factory->NewJSObject(isolate->object_function());
       if (detail->IsFailure()) return Object::cast(*detail);
 
       maybe_result = detail->SetProperty(*id_sym,
@@ -1568,10 +1588,10 @@
   }
 
   // Return the result as a JS array.
-  Handle<JSObject> lols = Factory::NewJSObject(Top::array_function());
+  Handle<JSObject> lols = factory->NewJSObject(isolate->array_function());
   Handle<JSArray>::cast(lols)->SetContent(*list);
 
-  Handle<JSObject> result = Factory::NewJSObject(Top::object_function());
+  Handle<JSObject> result = factory->NewJSObject(isolate->object_function());
   if (result->IsFailure()) return Object::cast(*result);
 
   maybe_result = result->SetProperty(*count_sym,
@@ -1580,14 +1600,14 @@
                                      kNonStrictMode);
   if (maybe_result->IsFailure()) return maybe_result;
 
-  Handle<String> first_sym = Factory::LookupAsciiSymbol("first_index");
+  Handle<String> first_sym = factory->LookupAsciiSymbol("first_index");
   maybe_result = result->SetProperty(*first_sym,
                                      Smi::FromInt(start_idx),
                                      NONE,
                                      kNonStrictMode);
   if (maybe_result->IsFailure()) return maybe_result;
 
-  Handle<String> lists_sym = Factory::LookupAsciiSymbol("lists");
+  Handle<String> lists_sym = factory->LookupAsciiSymbol("lists");
   maybe_result = result->SetProperty(*lists_sym,
                                      *lols,
                                      NONE,
@@ -1618,7 +1638,7 @@
   if (element != NULL) {
     return Object::cast(element->obj_);
   }
-  return Heap::undefined_value();
+  return HEAP->undefined_value();
 }
 
 
@@ -1639,8 +1659,11 @@
   SmartPointer<char> addr_str =
       address->ToCString(DISALLOW_NULLS, ROBUST_STRING_TRAVERSAL);
 
+  Isolate* isolate = Isolate::Current();
+
   // Extract the address value from the string.
-  int value = static_cast<int>(StringToInt(*address, 16));
+  int value =
+      static_cast<int>(StringToInt(isolate->unicode_cache(), *address, 16));
   Object* obj = reinterpret_cast<Object*>(value);
   return Smi::FromInt(GetObjId(obj));
 }
@@ -1760,10 +1783,13 @@
   Handle<String> desc;
   Handle<HeapObject> retainer;
 
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+
   // Prefetch some needed symbols.
-  Handle<String> id_sym = Factory::LookupAsciiSymbol("id");
-  Handle<String> desc_sym = Factory::LookupAsciiSymbol("desc");
-  Handle<String> size_sym = Factory::LookupAsciiSymbol("size");
+  Handle<String> id_sym = factory->LookupAsciiSymbol("id");
+  Handle<String> desc_sym = factory->LookupAsciiSymbol("desc");
+  Handle<String> size_sym = factory->LookupAsciiSymbol("size");
 
   NoHandleAllocation ha;
   int count = 0;
@@ -1774,7 +1800,7 @@
 
   // Iterate roots.
   LolVisitor lol_visitor(*target, target);
-  Heap::IterateStrongRoots(&lol_visitor, VISIT_ALL);
+  isolate->heap()->IterateStrongRoots(&lol_visitor, VISIT_ALL);
   if (!AddRootRetainerIfFound(lol_visitor,
                               filter,
                               summary,
@@ -1794,7 +1820,7 @@
   }
 
   lol_visitor.reset();
-  Heap::IterateWeakRoots(&lol_visitor, VISIT_ALL);
+  isolate->heap()->IterateWeakRoots(&lol_visitor, VISIT_ALL);
   if (!AddRootRetainerIfFound(lol_visitor,
                               filter,
                               summary,
@@ -1903,11 +1929,15 @@
                                              int start,
                                              int dump_limit,
                                              Handle<JSObject> filter_obj) {
-  HandleScope scope;
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+  Heap* heap = isolate->heap();
+
+  HandleScope scope(isolate);
 
   // Get the target object.
   HeapObject* heap_obj = HeapObject::cast(GetObj(obj_id));
-  if (heap_obj == Heap::undefined_value()) {
+  if (heap_obj == heap->undefined_value()) {
     return heap_obj;
   }
 
@@ -1915,7 +1945,7 @@
 
   // Get the constructor function for context extension and arguments array.
   JSObject* arguments_boilerplate =
-      Top::context()->global_context()->arguments_boilerplate();
+      isolate->context()->global_context()->arguments_boilerplate();
   JSFunction* arguments_function =
       JSFunction::cast(arguments_boilerplate->map()->constructor());
 
@@ -1937,7 +1967,7 @@
 
     // Set body.id.
     Handle<JSObject> body = Handle<JSObject>(JSObject::cast(body_obj));
-    Handle<String> id_sym = Factory::LookupAsciiSymbol("id");
+    Handle<String> id_sym = factory->LookupAsciiSymbol("id");
     maybe_result = body->SetProperty(*id_sym,
                                      Smi::FromInt(obj_id),
                                      NONE,
@@ -1952,13 +1982,17 @@
 Object* LiveObjectList::PrintObj(int obj_id) {
   Object* obj = GetObj(obj_id);
   if (!obj) {
-    return Heap::undefined_value();
+    return HEAP->undefined_value();
   }
 
   EmbeddedVector<char, 128> temp_filename;
   static int temp_count = 0;
   const char* path_prefix = ".";
 
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+  Heap* heap = isolate->heap();
+
   if (FLAG_lol_workdir) {
     path_prefix = FLAG_lol_workdir;
   }
@@ -1987,13 +2021,13 @@
   if (resource->exists() && !resource->is_empty()) {
     ASSERT(resource->IsAscii());
     Handle<String> dump_string =
-        Factory::NewExternalStringFromAscii(resource);
-    ExternalStringTable::AddString(*dump_string);
+        factory->NewExternalStringFromAscii(resource);
+    heap->external_string_table()->AddString(*dump_string);
     return *dump_string;
   } else {
     delete resource;
   }
-  return Heap::undefined_value();
+  return HEAP->undefined_value();
 }
 
 
@@ -2081,6 +2115,10 @@
 
   FILE* f = OS::FOpen(temp_filename.start(), "w+");
 
+  Isolate* isolate = Isolate::Current();
+  Factory* factory = isolate->factory();
+  Heap* heap = isolate->heap();
+
   // Save the previous verbosity.
   bool prev_verbosity = FLAG_use_verbose_printer;
   FLAG_use_verbose_printer = false;
@@ -2096,15 +2134,14 @@
       // Check for ObjectGroups that references this object.
       // TODO(mlam): refactor this to be more modular.
       {
-        List<ObjectGroup*>* groups = GlobalHandles::ObjectGroups();
+        List<ObjectGroup*>* groups = isolate->global_handles()->object_groups();
         for (int i = 0; i < groups->length(); i++) {
           ObjectGroup* group = groups->at(i);
           if (group == NULL) continue;
 
           bool found_group = false;
-          List<Object**>& objects = group->objects_;
-          for (int j = 0; j < objects.length(); j++) {
-            Object* object = *objects[j];
+          for (size_t j = 0; j < group->length_; j++) {
+            Object* object = *(group->objects_[j]);
             HeapObject* hobj = HeapObject::cast(object);
             if (obj2 == hobj) {
               found_group = true;
@@ -2117,8 +2154,8 @@
                    "obj %p is a member of object group %p {\n",
                    reinterpret_cast<void*>(obj2),
                    reinterpret_cast<void*>(group));
-            for (int j = 0; j < objects.length(); j++) {
-              Object* object = *objects[j];
+            for (size_t j = 0; j < group->length_; j++) {
+              Object* object = *(group->objects_[j]);
               if (!object->IsHeapObject()) continue;
 
               HeapObject* hobj = HeapObject::cast(object);
@@ -2143,12 +2180,12 @@
       }
 
       PrintF(f, "path from roots to obj %p\n", reinterpret_cast<void*>(obj2));
-      Heap::IterateRoots(&tracer, VISIT_ONLY_STRONG);
+      heap->IterateRoots(&tracer, VISIT_ONLY_STRONG);
       found = tracer.found();
 
       if (!found) {
         PrintF(f, "  No paths found. Checking symbol tables ...\n");
-        SymbolTable* symbol_table = Heap::raw_unchecked_symbol_table();
+        SymbolTable* symbol_table = HEAP->raw_unchecked_symbol_table();
         tracer.VisitPointers(reinterpret_cast<Object**>(&symbol_table),
                              reinterpret_cast<Object**>(&symbol_table)+1);
         found = tracer.found();
@@ -2161,7 +2198,7 @@
       if (!found) {
         PrintF(f, "  No paths found. Checking weak roots ...\n");
         // Check weak refs next.
-        GlobalHandles::IterateWeakRoots(&tracer);
+        isolate->global_handles()->IterateWeakRoots(&tracer);
         found = tracer.found();
       }
 
@@ -2191,13 +2228,13 @@
   if (resource->exists() && !resource->is_empty()) {
     ASSERT(resource->IsAscii());
     Handle<String> path_string =
-        Factory::NewExternalStringFromAscii(resource);
-    ExternalStringTable::AddString(*path_string);
+        factory->NewExternalStringFromAscii(resource);
+    heap->external_string_table()->AddString(*path_string);
     return *path_string;
   } else {
     delete resource;
   }
-  return Heap::undefined_value();
+  return heap->undefined_value();
 }
 
 
@@ -2210,13 +2247,13 @@
   HeapObject* obj1 = NULL;
   if (obj_id1 != 0) {
     obj1 = HeapObject::cast(GetObj(obj_id1));
-    if (obj1 == Heap::undefined_value()) {
+    if (obj1 == HEAP->undefined_value()) {
       return obj1;
     }
   }
 
   HeapObject* obj2 = HeapObject::cast(GetObj(obj_id2));
-  if (obj2 == Heap::undefined_value()) {
+  if (obj2 == HEAP->undefined_value()) {
     return obj2;
   }
 
@@ -2570,12 +2607,13 @@
 void LiveObjectList::VerifyNotInFromSpace() {
   OS::Print("VerifyNotInFromSpace() ...\n");
   LolIterator it(NULL, last());
+  Heap* heap = ISOLATE->heap();
   int i = 0;
   for (it.Init(); !it.Done(); it.Next()) {
     HeapObject* heap_obj = it.Obj();
-    if (Heap::InFromSpace(heap_obj)) {
+    if (heap->InFromSpace(heap_obj)) {
       OS::Print(" ERROR: VerifyNotInFromSpace: [%d] obj %p in From space %p\n",
-                i++, heap_obj, Heap::new_space()->FromSpaceLow());
+                i++, heap_obj, heap->new_space()->FromSpaceLow());
     }
   }
 }
diff --git a/src/liveobjectlist.h b/src/liveobjectlist.h
index 23e418d..542482d 100644
--- a/src/liveobjectlist.h
+++ b/src/liveobjectlist.h
@@ -237,10 +237,10 @@
   // to live new space objects, and not actually keep them alive.
   void UpdatePointer(Object** p) {
     Object* object = *p;
-    if (!Heap::InNewSpace(object)) return;
+    if (!HEAP->InNewSpace(object)) return;
 
     HeapObject* heap_obj = HeapObject::cast(object);
-    ASSERT(Heap::InFromSpace(heap_obj));
+    ASSERT(HEAP->InFromSpace(heap_obj));
 
     // We use the first word (where the map pointer usually is) of a heap
     // object to record the forwarding pointer.  A forwarding pointer can
diff --git a/src/log-utils.cc b/src/log-utils.cc
index 2d1ce23..27e654d 100644
--- a/src/log-utils.cc
+++ b/src/log-utils.cc
@@ -34,7 +34,7 @@
 namespace internal {
 
 
-const char* Log::kLogToTemporaryFile = "&";
+const char* const Log::kLogToTemporaryFile = "&";
 
 
 Log::Log(Logger* logger)
@@ -86,8 +86,6 @@
   if (open_log_file) {
     if (strcmp(FLAG_logfile, "-") == 0) {
       OpenStdout();
-    } else if (strcmp(FLAG_logfile, "*") == 0) {
-      // Does nothing for now. Will be removed.
     } else if (strcmp(FLAG_logfile, kLogToTemporaryFile) == 0) {
       OpenTemporaryFile();
     } else {
diff --git a/src/log-utils.h b/src/log-utils.h
index d336d71..2b20a01 100644
--- a/src/log-utils.h
+++ b/src/log-utils.h
@@ -59,7 +59,7 @@
 
   // This mode is only used in tests, as temporary files are automatically
   // deleted on close and thus can't be accessed afterwards.
-  static const char* kLogToTemporaryFile;
+  static const char* const kLogToTemporaryFile;
 
  private:
   explicit Log(Logger* logger);
diff --git a/src/log.cc b/src/log.cc
index 04fd22e..dedf7e9 100644
--- a/src/log.cc
+++ b/src/log.cc
@@ -1400,6 +1400,7 @@
       case Code::UNARY_OP_IC:   // fall through
       case Code::BINARY_OP_IC:   // fall through
       case Code::COMPARE_IC:  // fall through
+      case Code::TO_BOOLEAN_IC:  // fall through
       case Code::STUB:
         description =
             CodeStub::MajorName(CodeStub::GetMajorKey(code_object), true);
diff --git a/src/macros.py b/src/macros.py
index fc08cb1..5ba7ac3 100644
--- a/src/macros.py
+++ b/src/macros.py
@@ -44,7 +44,7 @@
 const kApiConstructorOffset         = 2;
 const kApiPrototypeTemplateOffset   = 5;
 const kApiParentTemplateOffset      = 6;
-const kApiPrototypeAttributesOffset = 15;
+const kApiFlagOffset                = 14;
 
 const NO_HINT     = 0;
 const NUMBER_HINT = 1;
@@ -65,6 +65,7 @@
 
 # For apinatives.js
 const kUninitialized = -1;
+const kReadOnlyPrototypeBit = 3;  # For FunctionTemplateInfo, matches objects.h
 
 # Note: kDayZeroInJulianDay = ToJulianDay(1970, 0, 1).
 const kInvalidDate        = 'Invalid Date';
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 0bf8286..3e4a617 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -64,13 +64,15 @@
       live_bytes_(0),
 #endif
       heap_(NULL),
-      code_flusher_(NULL) { }
+      code_flusher_(NULL),
+      encountered_weak_maps_(NULL) { }
 
 
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
   ASSERT(state_ == PREPARE_GC);
+  ASSERT(encountered_weak_maps_ == Smi::FromInt(0));
 
   // Prepare has selected whether to compact the old generation or not.
   // Tell the tracer.
@@ -80,6 +82,8 @@
 
   if (FLAG_collect_maps) ClearNonLiveTransitions();
 
+  ClearWeakMaps();
+
   SweepLargeObjectSpace();
 
   if (IsCompacting()) {
@@ -390,6 +394,10 @@
                                       ConsString::BodyDescriptor,
                                       void>::Visit);
 
+    table_.Register(kVisitSlicedString,
+                    &FixedBodyVisitor<StaticMarkingVisitor,
+                                      SlicedString::BodyDescriptor,
+                                      void>::Visit);
 
     table_.Register(kVisitFixedArray,
                     &FlexibleBodyVisitor<StaticMarkingVisitor,
@@ -407,6 +415,8 @@
     table_.Register(kVisitSeqAsciiString, &DataObjectVisitor::Visit);
     table_.Register(kVisitSeqTwoByteString, &DataObjectVisitor::Visit);
 
+    table_.Register(kVisitJSWeakMap, &VisitJSWeakMap);
+
     table_.Register(kVisitOddball,
                     &FixedBodyVisitor<StaticMarkingVisitor,
                                       Oddball::BodyDescriptor,
@@ -556,6 +566,34 @@
                               StructBodyDescriptor,
                               void> StructObjectVisitor;
 
+  static void VisitJSWeakMap(Map* map, HeapObject* object) {
+    MarkCompactCollector* collector = map->heap()->mark_compact_collector();
+    JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(object);
+
+    // Enqueue weak map in linked list of encountered weak maps.
+    ASSERT(weak_map->next() == Smi::FromInt(0));
+    weak_map->set_next(collector->encountered_weak_maps());
+    collector->set_encountered_weak_maps(weak_map);
+
+    // Skip visiting the backing hash table containing the mappings.
+    int object_size = JSWeakMap::BodyDescriptor::SizeOf(map, object);
+    BodyVisitorBase<StaticMarkingVisitor>::IteratePointers(
+        map->heap(),
+        object,
+        JSWeakMap::BodyDescriptor::kStartOffset,
+        JSWeakMap::kTableOffset);
+    BodyVisitorBase<StaticMarkingVisitor>::IteratePointers(
+        map->heap(),
+        object,
+        JSWeakMap::kTableOffset + kPointerSize,
+        object_size);
+
+    // Mark the backing hash table without pushing it on the marking stack.
+    ASSERT(!weak_map->unchecked_table()->IsMarked());
+    ASSERT(weak_map->unchecked_table()->map()->IsMarked());
+    collector->SetMark(weak_map->unchecked_table());
+  }
+
   static void VisitCode(Map* map, HeapObject* object) {
     reinterpret_cast<Code*>(object)->CodeIterateBody<StaticMarkingVisitor>(
         map->heap());
@@ -1369,20 +1407,26 @@
 // marking stack have been marked, or are overflowed in the heap.
 void MarkCompactCollector::EmptyMarkingStack() {
   while (!marking_stack_.is_empty()) {
-    HeapObject* object = marking_stack_.Pop();
-    ASSERT(object->IsHeapObject());
-    ASSERT(heap()->Contains(object));
-    ASSERT(object->IsMarked());
-    ASSERT(!object->IsOverflowed());
+    while (!marking_stack_.is_empty()) {
+      HeapObject* object = marking_stack_.Pop();
+      ASSERT(object->IsHeapObject());
+      ASSERT(heap()->Contains(object));
+      ASSERT(object->IsMarked());
+      ASSERT(!object->IsOverflowed());
 
-    // Because the object is marked, we have to recover the original map
-    // pointer and use it to mark the object's body.
-    MapWord map_word = object->map_word();
-    map_word.ClearMark();
-    Map* map = map_word.ToMap();
-    MarkObject(map);
+      // Because the object is marked, we have to recover the original map
+      // pointer and use it to mark the object's body.
+      MapWord map_word = object->map_word();
+      map_word.ClearMark();
+      Map* map = map_word.ToMap();
+      MarkObject(map);
 
-    StaticMarkingVisitor::IterateBody(map, object);
+      StaticMarkingVisitor::IterateBody(map, object);
+    }
+
+    // Process encountered weak maps, mark objects only reachable by those
+    // weak maps and repeat until fix-point is reached.
+    ProcessWeakMaps();
   }
 }
 
@@ -1735,6 +1779,45 @@
   }
 }
 
+
+void MarkCompactCollector::ProcessWeakMaps() {
+  Object* weak_map_obj = encountered_weak_maps();
+  while (weak_map_obj != Smi::FromInt(0)) {
+    ASSERT(HeapObject::cast(weak_map_obj)->IsMarked());
+    JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj);
+    ObjectHashTable* table = weak_map->unchecked_table();
+    for (int i = 0; i < table->Capacity(); i++) {
+      if (HeapObject::cast(table->KeyAt(i))->IsMarked()) {
+        Object* value = table->get(table->EntryToValueIndex(i));
+        StaticMarkingVisitor::MarkObjectByPointer(heap(), &value);
+        table->set_unchecked(heap(),
+                             table->EntryToValueIndex(i),
+                             value,
+                             UPDATE_WRITE_BARRIER);
+      }
+    }
+    weak_map_obj = weak_map->next();
+  }
+}
+
+
+void MarkCompactCollector::ClearWeakMaps() {
+  Object* weak_map_obj = encountered_weak_maps();
+  while (weak_map_obj != Smi::FromInt(0)) {
+    ASSERT(HeapObject::cast(weak_map_obj)->IsMarked());
+    JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj);
+    ObjectHashTable* table = weak_map->unchecked_table();
+    for (int i = 0; i < table->Capacity(); i++) {
+      if (!HeapObject::cast(table->KeyAt(i))->IsMarked()) {
+        table->RemoveEntry(i, heap());
+      }
+    }
+    weak_map_obj = weak_map->next();
+    weak_map->set_next(Smi::FromInt(0));
+  }
+  set_encountered_weak_maps(Smi::FromInt(0));
+}
+
 // -------------------------------------------------------------------------
 // Phase 2: Encode forwarding addresses.
 // When compacting, forwarding addresses for objects in old space and map
diff --git a/src/mark-compact.h b/src/mark-compact.h
index 179edba..9b67c8a 100644
--- a/src/mark-compact.h
+++ b/src/mark-compact.h
@@ -193,6 +193,11 @@
   inline bool is_code_flushing_enabled() const { return code_flusher_ != NULL; }
   void EnableCodeFlushing(bool enable);
 
+  inline Object* encountered_weak_maps() { return encountered_weak_maps_; }
+  inline void set_encountered_weak_maps(Object* weak_map) {
+    encountered_weak_maps_ = weak_map;
+  }
+
  private:
   MarkCompactCollector();
   ~MarkCompactCollector();
@@ -329,6 +334,16 @@
   // We replace them with a null descriptor, with the same key.
   void ClearNonLiveTransitions();
 
+  // Mark all values associated with reachable keys in weak maps encountered
+  // so far.  This might push new object or even new weak maps onto the
+  // marking stack.
+  void ProcessWeakMaps();
+
+  // After all reachable objects have been marked those weak map entries
+  // with an unreachable key are removed from all encountered weak maps.
+  // The linked list of all encountered weak maps is destroyed.
+  void ClearWeakMaps();
+
   // -----------------------------------------------------------------------
   // Phase 2: Sweeping to clear mark bits and free non-live objects for
   // a non-compacting collection, or else computing and encoding
@@ -499,6 +514,7 @@
   Heap* heap_;
   MarkingStack marking_stack_;
   CodeFlusher* code_flusher_;
+  Object* encountered_weak_maps_;
 
   friend class Heap;
   friend class OverflowedObjectsScanner;
diff --git a/src/messages.js b/src/messages.js
index 0b314a4..845ca07 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -198,17 +198,19 @@
       non_extensible_proto:         ["%0", " is not extensible"],
       handler_non_object:           ["Proxy.", "%0", " called with non-object as handler"],
       handler_trap_missing:         ["Proxy handler ", "%0", " has no '", "%1", "' trap"],
+      handler_trap_must_be_callable: ["Proxy handler ", "%0", " has non-callable '", "%1", "' trap"],
       handler_returned_false:       ["Proxy handler ", "%0", " returned false for '", "%1", "' trap"],
       handler_returned_undefined:   ["Proxy handler ", "%0", " returned undefined for '", "%1", "' trap"],
       proxy_prop_not_configurable:  ["Trap ", "%1", " of proxy handler ", "%0", " returned non-configurable descriptor for property ", "%2"],
       proxy_non_object_prop_names:  ["Trap ", "%1", " returned non-object ", "%0"],
       proxy_repeated_prop_name:     ["Trap ", "%1", " returned repeated property name ", "%2"],
+      invalid_weakmap_key:          ["Invalid value used as weak map key"],
       // RangeError
       invalid_array_length:         ["Invalid array length"],
       stack_overflow:               ["Maximum call stack size exceeded"],
       // SyntaxError
       unable_to_parse:              ["Parse error"],
-      duplicate_regexp_flag:        ["Duplicate RegExp flag ", "%0"],
+      invalid_regexp_flags:         ["Invalid flags supplied to RegExp constructor '", "%0", "'"],
       invalid_regexp:               ["Invalid RegExp pattern /", "%0", "/"],
       illegal_break:                ["Illegal break statement"],
       illegal_continue:             ["Illegal continue statement"],
@@ -248,8 +250,9 @@
       strict_cannot_assign:         ["Cannot assign to read only '", "%0", "' in strict mode"],
       strict_poison_pill:           ["'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them"],
       strict_caller:                ["Illegal access to a strict mode caller function."],
+      unprotected_let:              ["Illegal let declaration in unprotected statement context."],
       cant_prevent_ext_external_array_elements: ["Cannot prevent extension of an object with external array elements"],
-      redef_external_array_element: ["Cannot redefine a property of an object"]
+      redef_external_array_element: ["Cannot redefine a property of an object with external array elements"],
     };
   }
   var message_type = %MessageGetType(message);
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index 51642e0..28ac557 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -780,10 +780,10 @@
 void Assembler::next(Label* L) {
   ASSERT(L->is_linked());
   int link = target_at(L->pos());
-  ASSERT(link > 0 || link == kEndOfChain);
   if (link == kEndOfChain) {
     L->Unuse();
-  } else if (link > 0) {
+  } else {
+    ASSERT(link >= 0);
     L->link_to(link);
   }
 }
diff --git a/src/mips/assembler-mips.h b/src/mips/assembler-mips.h
index a16cd80..e5077be 100644
--- a/src/mips/assembler-mips.h
+++ b/src/mips/assembler-mips.h
@@ -127,38 +127,38 @@
 
 const Register no_reg = { -1 };
 
-const Register zero_reg = { 0 };
-const Register at = { 1 };
-const Register v0 = { 2 };
-const Register v1 = { 3 };
-const Register a0 = { 4 };
+const Register zero_reg = { 0 };  // Always zero.
+const Register at = { 1 };   // at: Reserved for synthetic instructions.
+const Register v0 = { 2 };   // v0, v1: Used when returning multiple values
+const Register v1 = { 3 };   //   from subroutines.
+const Register a0 = { 4 };   // a0 - a4: Used to pass non-FP parameters.
 const Register a1 = { 5 };
 const Register a2 = { 6 };
 const Register a3 = { 7 };
-const Register t0 = { 8 };
-const Register t1 = { 9 };
-const Register t2 = { 10 };
+const Register t0 = { 8 };   // t0 - t9: Can be used without reservation, act
+const Register t1 = { 9 };   //   as temporary registers and are allowed to
+const Register t2 = { 10 };  //   be destroyed by subroutines.
 const Register t3 = { 11 };
 const Register t4 = { 12 };
 const Register t5 = { 13 };
 const Register t6 = { 14 };
 const Register t7 = { 15 };
-const Register s0 = { 16 };
-const Register s1 = { 17 };
-const Register s2 = { 18 };
-const Register s3 = { 19 };
-const Register s4 = { 20 };
+const Register s0 = { 16 };  // s0 - s7: Subroutine register variables.
+const Register s1 = { 17 };  //   Subroutines that write to these registers
+const Register s2 = { 18 };  //   must restore their values before exiting so
+const Register s3 = { 19 };  //   that the caller can expect the values to be
+const Register s4 = { 20 };  //   preserved.
 const Register s5 = { 21 };
 const Register s6 = { 22 };
 const Register s7 = { 23 };
 const Register t8 = { 24 };
 const Register t9 = { 25 };
-const Register k0 = { 26 };
-const Register k1 = { 27 };
-const Register gp = { 28 };
-const Register sp = { 29 };
-const Register s8_fp = { 30 };
-const Register ra = { 31 };
+const Register k0 = { 26 };  // k0, k1: Reserved for system calls and
+const Register k1 = { 27 };  // interrupt handlers.
+const Register gp = { 28 };  // gp: Reserved.
+const Register sp = { 29 };  // sp: Stack pointer.
+const Register s8_fp = { 30 };  // fp: Frame pointer.
+const Register ra = { 31 };  // ra: Return address pointer.
 
 
 int ToNumber(Register reg);
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index d89d3e5..9385f2f 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -2506,7 +2506,7 @@
         CpuFeatures::Scope scope(FPU);
         __ mtc1(a2, f0);
         if (op_ == Token::SHR) {
-          __ Cvt_d_uw(f0, f0);
+          __ Cvt_d_uw(f0, f0, f22);
         } else {
           __ cvt_d_w(f0, f0);
         }
@@ -2920,7 +2920,7 @@
         } else {
           // The result must be interpreted as an unsigned 32-bit integer.
           __ mtc1(a2, double_scratch);
-          __ Cvt_d_uw(double_scratch, double_scratch);
+          __ Cvt_d_uw(double_scratch, double_scratch, single_scratch);
         }
 
         // Store the result.
@@ -3693,10 +3693,10 @@
   // args
 
   // Save callee saved registers on the stack.
-  __ MultiPush((kCalleeSaved | ra.bit()) & ~sp.bit());
+  __ MultiPush(kCalleeSaved | ra.bit());
 
   // Load argv in s0 register.
-  __ lw(s0, MemOperand(sp, kNumCalleeSaved * kPointerSize +
+  __ lw(s0, MemOperand(sp, (kNumCalleeSaved + 1) * kPointerSize +
                            StandardFrameConstants::kCArgsSlotsSize));
 
   // We build an EntryFrame.
@@ -3830,7 +3830,7 @@
   __ addiu(sp, sp, -EntryFrameConstants::kCallerFPOffset);
 
   // Restore callee saved registers from the stack.
-  __ MultiPop((kCalleeSaved | ra.bit()) & ~sp.bit());
+  __ MultiPop(kCalleeSaved | ra.bit());
   // Return.
   __ Jump(ra);
 }
@@ -4517,6 +4517,9 @@
   __ Addu(a2, a2, Operand(RegExpImpl::kLastMatchOverhead));
   __ sra(at, a0, kSmiTagSize);  // Untag length for comparison.
   __ Branch(&runtime, gt, a2, Operand(at));
+
+  // Reset offset for possibly sliced string.
+  __ mov(t0, zero_reg);
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
   // Check the representation and encoding of the subject string.
@@ -4524,29 +4527,41 @@
   __ lw(a0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ lbu(a0, FieldMemOperand(a0, Map::kInstanceTypeOffset));
   // First check for flat string.
-  __ And(at, a0, Operand(kIsNotStringMask | kStringRepresentationMask));
+  __ And(a1, a0, Operand(kIsNotStringMask | kStringRepresentationMask));
   STATIC_ASSERT((kStringTag | kSeqStringTag) == 0);
-  __ Branch(&seq_string, eq, at, Operand(zero_reg));
+  __ Branch(&seq_string, eq, a1, Operand(zero_reg));
 
   // subject: Subject string
   // a0: instance type if Subject string
   // regexp_data: RegExp data (FixedArray)
-  // Check for flat cons string.
+  // Check for flat cons string or sliced string.
   // A flat cons string is a cons string where the second part is the empty
   // string. In that case the subject string is just the first part of the cons
   // string. Also in this case the first part of the cons string is known to be
   // a sequential string or an external string.
-  STATIC_ASSERT(kExternalStringTag != 0);
-  STATIC_ASSERT((kConsStringTag & kExternalStringTag) == 0);
-  __ And(at, a0, Operand(kIsNotStringMask | kExternalStringTag));
-  __ Branch(&runtime, ne, at, Operand(zero_reg));
+  // In the case of a sliced string its offset has to be taken into account.
+  Label cons_string, check_encoding;
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ Branch(&cons_string, lt, a1, Operand(kExternalStringTag));
+  __ Branch(&runtime, eq, a1, Operand(kExternalStringTag));
+
+  // String is sliced.
+  __ lw(t0, FieldMemOperand(subject, SlicedString::kOffsetOffset));
+  __ sra(t0, t0, kSmiTagSize);
+  __ lw(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
+  // t5: offset of sliced string, smi-tagged.
+  __ jmp(&check_encoding);
+  // String is a cons string, check whether it is flat.
+  __ bind(&cons_string);
   __ lw(a0, FieldMemOperand(subject, ConsString::kSecondOffset));
   __ LoadRoot(a1, Heap::kEmptyStringRootIndex);
   __ Branch(&runtime, ne, a0, Operand(a1));
   __ lw(subject, FieldMemOperand(subject, ConsString::kFirstOffset));
+  // Is first part of cons or parent of slice a flat string?
+  __ bind(&check_encoding);
   __ lw(a0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ lbu(a0, FieldMemOperand(a0, Map::kInstanceTypeOffset));
-  // Is first part a flat string?
   STATIC_ASSERT(kSeqStringTag == 0);
   __ And(at, a0, Operand(kStringRepresentationMask));
   __ Branch(&runtime, ne, at, Operand(zero_reg));
@@ -4562,8 +4577,8 @@
   __ And(a0, a0, Operand(kStringEncodingMask));  // Non-zero for ascii.
   __ lw(t9, FieldMemOperand(regexp_data, JSRegExp::kDataAsciiCodeOffset));
   __ sra(a3, a0, 2);  // a3 is 1 for ascii, 0 for UC16 (usyed below).
-  __ lw(t0, FieldMemOperand(regexp_data, JSRegExp::kDataUC16CodeOffset));
-  __ movz(t9, t0, a0);  // If UC16 (a0 is 0), replace t9 w/kDataUC16CodeOffset.
+  __ lw(t1, FieldMemOperand(regexp_data, JSRegExp::kDataUC16CodeOffset));
+  __ movz(t9, t1, a0);  // If UC16 (a0 is 0), replace t9 w/kDataUC16CodeOffset.
 
   // Check that the irregexp code has been generated for the actual string
   // encoding. If it has, the field contains a code object otherwise it contains
@@ -4630,23 +4645,32 @@
 
   // For arguments 4 and 3 get string length, calculate start of string data
   // and calculate the shift of the index (0 for ASCII and 1 for two byte).
-  __ lw(a0, FieldMemOperand(subject, String::kLengthOffset));
-  __ sra(a0, a0, kSmiTagSize);
   STATIC_ASSERT(SeqAsciiString::kHeaderSize == SeqTwoByteString::kHeaderSize);
-  __ Addu(t0, subject, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ Addu(t2, subject, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
   __ Xor(a3, a3, Operand(1));  // 1 for 2-byte str, 0 for 1-byte.
-  // Argument 4 (a3): End of string data
-  // Argument 3 (a2): Start of string data
+  // Load the length from the original subject string from the previous stack
+  // frame. Therefore we have to use fp, which points exactly to two pointer
+  // sizes below the previous sp. (Because creating a new stack frame pushes
+  // the previous fp onto the stack and moves up sp by 2 * kPointerSize.)
+  __ lw(a0, MemOperand(fp, kSubjectOffset + 2 * kPointerSize));
+  // If slice offset is not 0, load the length from the original sliced string.
+  // Argument 4, a3: End of string data
+  // Argument 3, a2: Start of string data
+  // Prepare start and end index of the input.
+  __ sllv(t1, t0, a3);
+  __ addu(t0, t2, t1);
   __ sllv(t1, a1, a3);
   __ addu(a2, t0, t1);
-  __ sllv(t1, a0, a3);
-  __ addu(a3, t0, t1);
 
+  __ lw(t2, FieldMemOperand(a0, String::kLengthOffset));
+  __ sra(t2, t2, kSmiTagSize);
+  __ sllv(t1, t2, a3);
+  __ addu(a3, t0, t1);
   // Argument 2 (a1): Previous index.
   // Already there
 
   // Argument 1 (a0): Subject string.
-  __ mov(a0, subject);
+  // Already there
 
   // Locate the code entry and call it.
   __ Addu(t9, t9, Operand(Code::kHeaderSize - kHeapObjectTag));
@@ -4663,11 +4687,14 @@
   // Check the result.
 
   Label success;
-  __ Branch(&success, eq, v0, Operand(NativeRegExpMacroAssembler::SUCCESS));
+  __ Branch(&success, eq,
+            subject, Operand(NativeRegExpMacroAssembler::SUCCESS));
   Label failure;
-  __ Branch(&failure, eq, v0, Operand(NativeRegExpMacroAssembler::FAILURE));
+  __ Branch(&failure, eq,
+            subject, Operand(NativeRegExpMacroAssembler::FAILURE));
   // If not exception it can only be retry. Handle that in the runtime system.
-  __ Branch(&runtime, ne, v0, Operand(NativeRegExpMacroAssembler::EXCEPTION));
+  __ Branch(&runtime, ne,
+            subject, Operand(NativeRegExpMacroAssembler::EXCEPTION));
   // Result must now be exception. If there is no pending exception already a
   // stack overflow (on the backtrack stack) was detected in RegExp code but
   // haven't created the exception yet. Handle that in the runtime system.
@@ -4678,16 +4705,16 @@
   __ li(a2, Operand(ExternalReference(Isolate::k_pending_exception_address,
                                       masm->isolate())));
   __ lw(v0, MemOperand(a2, 0));
-  __ Branch(&runtime, eq, v0, Operand(a1));
+  __ Branch(&runtime, eq, subject, Operand(a1));
 
   __ sw(a1, MemOperand(a2, 0));  // Clear pending exception.
 
   // Check if the exception is a termination. If so, throw as uncatchable.
   __ LoadRoot(a0, Heap::kTerminationExceptionRootIndex);
   Label termination_exception;
-  __ Branch(&termination_exception, eq, v0, Operand(a0));
+  __ Branch(&termination_exception, eq, subject, Operand(a0));
 
-  __ Throw(a0);  // Expects thrown value in v0.
+  __ Throw(subject);  // Expects thrown value in v0.
 
   __ bind(&termination_exception);
   __ ThrowUncatchable(TERMINATION, v0);  // Expects thrown value in v0.
@@ -4963,6 +4990,7 @@
   Label flat_string;
   Label ascii_string;
   Label got_char_code;
+  Label sliced_string;
 
   ASSERT(!t0.is(scratch_));
   ASSERT(!t0.is(index_));
@@ -4996,23 +5024,37 @@
   __ Branch(&flat_string, eq, t0, Operand(zero_reg));
 
   // Handle non-flat strings.
-  __ And(t0, result_, Operand(kIsConsStringMask));
-  __ Branch(&call_runtime_, eq, t0, Operand(zero_reg));
+  __ And(result_, result_, Operand(kStringRepresentationMask));
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ Branch(&sliced_string, gt, result_, Operand(kExternalStringTag));
+  __ Branch(&call_runtime_, eq, result_, Operand(kExternalStringTag));
 
   // ConsString.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
+  Label assure_seq_string;
   __ lw(result_, FieldMemOperand(object_, ConsString::kSecondOffset));
   __ LoadRoot(t0, Heap::kEmptyStringRootIndex);
   __ Branch(&call_runtime_, ne, result_, Operand(t0));
 
   // Get the first of the two strings and load its instance type.
   __ lw(object_, FieldMemOperand(object_, ConsString::kFirstOffset));
+  __ jmp(&assure_seq_string);
+
+  // SlicedString, unpack and add offset.
+  __ bind(&sliced_string);
+  __ lw(result_, FieldMemOperand(object_, SlicedString::kOffsetOffset));
+  __ addu(scratch_, scratch_, result_);
+  __ lw(object_, FieldMemOperand(object_, SlicedString::kParentOffset));
+
+  // Assure that we are dealing with a sequential string. Go to runtime if not.
+  __ bind(&assure_seq_string);
   __ lw(result_, FieldMemOperand(object_, HeapObject::kMapOffset));
   __ lbu(result_, FieldMemOperand(result_, Map::kInstanceTypeOffset));
-  // If the first cons component is also non-flat, then go to runtime.
+  // Check that parent is not an external string. Go to runtime otherwise.
   STATIC_ASSERT(kSeqStringTag == 0);
 
   __ And(t0, result_, Operand(kStringRepresentationMask));
@@ -5583,6 +5625,11 @@
   Register to = t2;
   Register from = t3;
 
+  if (FLAG_string_slices) {
+    __ nop();  // Jumping as first instruction would crash the code generation.
+    __ jmp(&sub_string_runtime);
+  }
+
   // Check bounds and smi-ness.
   __ lw(to, MemOperand(sp, kToOffset));
   __ lw(from, MemOperand(sp, kFromOffset));
diff --git a/src/mips/deoptimizer-mips.cc b/src/mips/deoptimizer-mips.cc
index 9a19aba..18b6231 100644
--- a/src/mips/deoptimizer-mips.cc
+++ b/src/mips/deoptimizer-mips.cc
@@ -39,7 +39,7 @@
 namespace internal {
 
 
-int Deoptimizer::table_entry_size_ = 10;
+const int Deoptimizer::table_entry_size_ = 10;
 
 
 int Deoptimizer::patch_size() {
diff --git a/src/mips/frames-mips.h b/src/mips/frames-mips.h
index 2e720fb..1899843 100644
--- a/src/mips/frames-mips.h
+++ b/src/mips/frames-mips.h
@@ -59,10 +59,10 @@
   // Saved temporaries.
   1 << 16 | 1 << 17 | 1 << 18 | 1 << 19 |
   1 << 20 | 1 << 21 | 1 << 22 | 1 << 23 |
-  // gp, sp, fp.
-  1 << 28 | 1 << 29 | 1 << 30;
+  // fp.
+  1 << 30;
 
-static const int kNumCalleeSaved = 11;
+static const int kNumCalleeSaved = 9;
 
 
 // Number of registers for which space is reserved in safepoints. Must be a
@@ -121,10 +121,11 @@
 
 class StackHandlerConstants : public AllStatic {
  public:
-  static const int kNextOffset  = 0 * kPointerSize;
-  static const int kStateOffset = 1 * kPointerSize;
-  static const int kFPOffset    = 2 * kPointerSize;
-  static const int kPCOffset    = 3 * kPointerSize;
+  static const int kNextOffset    = 0 * kPointerSize;
+  static const int kStateOffset   = 1 * kPointerSize;
+  static const int kContextOffset = 2 * kPointerSize;
+  static const int kFPOffset      = 3 * kPointerSize;
+  static const int kPCOffset      = 4 * kPointerSize;
 
   static const int kSize = kPCOffset + kPointerSize;
 };
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index 7834273..d3f8922 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -55,7 +55,6 @@
 
 
 static unsigned GetPropertyId(Property* property) {
-  if (property->is_synthetic()) return AstNode::kNoNumber;
   return property->id();
 }
 
@@ -697,109 +696,77 @@
   Comment cmnt(masm_, "[ Declaration");
   ASSERT(variable != NULL);  // Must have been resolved.
   Slot* slot = variable->AsSlot();
-  Property* prop = variable->AsProperty();
-
-  if (slot != NULL) {
-    switch (slot->type()) {
-      case Slot::PARAMETER:
-      case Slot::LOCAL:
-        if (mode == Variable::CONST) {
-          __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
-          __ sw(t0, MemOperand(fp, SlotOffset(slot)));
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ sw(result_register(), MemOperand(fp, SlotOffset(slot)));
-        }
-        break;
-
-      case Slot::CONTEXT:
-        // We bypass the general EmitSlotSearch because we know more about
-        // this specific context.
-
-        // The variable in the decl always resides in the current function
-        // context.
-        ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
-        if (FLAG_debug_code) {
-          // Check that we're not inside a with or catch context.
-          __ lw(a1, FieldMemOperand(cp, HeapObject::kMapOffset));
-          __ LoadRoot(t0, Heap::kWithContextMapRootIndex);
-          __ Check(ne, "Declaration in with context.",
-                   a1, Operand(t0));
-          __ LoadRoot(t0, Heap::kCatchContextMapRootIndex);
-          __ Check(ne, "Declaration in catch context.",
-                   a1, Operand(t0));
-        }
-        if (mode == Variable::CONST) {
-          __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
-          __ sw(at, ContextOperand(cp, slot->index()));
-          // No write barrier since the_hole_value is in old space.
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ sw(result_register(), ContextOperand(cp, slot->index()));
-          int offset = Context::SlotOffset(slot->index());
-          // We know that we have written a function, which is not a smi.
-          __ mov(a1, cp);
-          __ RecordWrite(a1, Operand(offset), a2, result_register());
-        }
-        break;
-
-      case Slot::LOOKUP: {
-        __ li(a2, Operand(variable->name()));
-        // Declaration nodes are always introduced in one of two modes.
-        ASSERT(mode == Variable::VAR ||
-               mode == Variable::CONST);
-        PropertyAttributes attr =
-            (mode == Variable::VAR) ? NONE : READ_ONLY;
-        __ li(a1, Operand(Smi::FromInt(attr)));
-        // Push initial value, if any.
-        // Note: For variables we must not push an initial value (such as
-        // 'undefined') because we may have a (legal) redeclaration and we
-        // must not destroy the current value.
-        if (mode == Variable::CONST) {
-          __ LoadRoot(a0, Heap::kTheHoleValueRootIndex);
-          __ Push(cp, a2, a1, a0);
-        } else if (function != NULL) {
-          __ Push(cp, a2, a1);
-          // Push initial value for function declaration.
-          VisitForStackValue(function);
-        } else {
-          ASSERT(Smi::FromInt(0) == 0);
-          // No initial value!
-          __ mov(a0, zero_reg);  // Operand(Smi::FromInt(0)));
-          __ Push(cp, a2, a1, a0);
-        }
-        __ CallRuntime(Runtime::kDeclareContextSlot, 4);
-        break;
+  ASSERT(slot != NULL);
+  switch (slot->type()) {
+    case Slot::PARAMETER:
+    case Slot::LOCAL:
+      if (mode == Variable::CONST) {
+        __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
+        __ sw(t0, MemOperand(fp, SlotOffset(slot)));
+      } else if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ sw(result_register(), MemOperand(fp, SlotOffset(slot)));
       }
-    }
+      break;
 
-  } else if (prop != NULL) {
-    // A const declaration aliasing a parameter is an illegal redeclaration.
-    ASSERT(mode != Variable::CONST);
-    if (function != NULL) {
-      // We are declaring a function that rewrites to a property.
-      // Use (keyed) IC to set the initial value.  We cannot visit the
-      // rewrite because it's shared and we risk recording duplicate AST
-      // IDs for bailouts from optimized code.
-      ASSERT(prop->obj()->AsVariableProxy() != NULL);
-      { AccumulatorValueContext for_object(this);
-        EmitVariableLoad(prop->obj()->AsVariableProxy());
+    case Slot::CONTEXT:
+      // We bypass the general EmitSlotSearch because we know more about
+      // this specific context.
+
+      // The variable in the decl always resides in the current function
+      // context.
+      ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
+      if (FLAG_debug_code) {
+        // Check that we're not inside a with or catch context.
+        __ lw(a1, FieldMemOperand(cp, HeapObject::kMapOffset));
+        __ LoadRoot(t0, Heap::kWithContextMapRootIndex);
+        __ Check(ne, "Declaration in with context.",
+                 a1, Operand(t0));
+        __ LoadRoot(t0, Heap::kCatchContextMapRootIndex);
+        __ Check(ne, "Declaration in catch context.",
+                 a1, Operand(t0));
       }
+      if (mode == Variable::CONST) {
+        __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+        __ sw(at, ContextOperand(cp, slot->index()));
+        // No write barrier since the_hole_value is in old space.
+      } else if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ sw(result_register(), ContextOperand(cp, slot->index()));
+        int offset = Context::SlotOffset(slot->index());
+        // We know that we have written a function, which is not a smi.
+        __ mov(a1, cp);
+        __ RecordWrite(a1, Operand(offset), a2, result_register());
+      }
+      break;
 
-      __ push(result_register());
-      VisitForAccumulatorValue(function);
-      __ mov(a0, result_register());
-      __ pop(a2);
-
-      ASSERT(prop->key()->AsLiteral() != NULL &&
-             prop->key()->AsLiteral()->handle()->IsSmi());
-      __ li(a1, Operand(prop->key()->AsLiteral()->handle()));
-
-      Handle<Code> ic = is_strict_mode()
-          ? isolate()->builtins()->KeyedStoreIC_Initialize_Strict()
-          : isolate()->builtins()->KeyedStoreIC_Initialize();
-      __ Call(ic);
-      // Value in v0 is ignored (declarations are statements).
+    case Slot::LOOKUP: {
+      __ li(a2, Operand(variable->name()));
+      // Declaration nodes are always introduced in one of two modes.
+      ASSERT(mode == Variable::VAR ||
+             mode == Variable::CONST ||
+             mode == Variable::LET);
+      PropertyAttributes attr = (mode == Variable::CONST) ? READ_ONLY : NONE;
+      __ li(a1, Operand(Smi::FromInt(attr)));
+      // Push initial value, if any.
+      // Note: For variables we must not push an initial value (such as
+      // 'undefined') because we may have a (legal) redeclaration and we
+      // must not destroy the current value.
+      if (mode == Variable::CONST) {
+        __ LoadRoot(a0, Heap::kTheHoleValueRootIndex);
+        __ Push(cp, a2, a1, a0);
+      } else if (function != NULL) {
+        __ Push(cp, a2, a1);
+        // Push initial value for function declaration.
+        VisitForStackValue(function);
+      } else {
+        ASSERT(Smi::FromInt(0) == 0);
+        // No initial value!
+        __ mov(a0, zero_reg);  // Operand(Smi::FromInt(0)));
+        __ Push(cp, a2, a1, a0);
+      }
+      __ CallRuntime(Runtime::kDeclareContextSlot, 4);
+      break;
     }
   }
 }
@@ -886,7 +853,7 @@
   __ bind(&next_test);
   __ Drop(1);  // Switch value is no longer needed.
   if (default_clause == NULL) {
-    __ Branch(nested_statement.break_target());
+    __ Branch(nested_statement.break_label());
   } else {
     __ Branch(default_clause->body_target());
   }
@@ -900,7 +867,7 @@
     VisitStatements(clause->statements());
   }
 
-  __ bind(nested_statement.break_target());
+  __ bind(nested_statement.break_label());
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
 }
 
@@ -1026,7 +993,7 @@
   // Load the current count to a0, load the length to a1.
   __ lw(a0, MemOperand(sp, 0 * kPointerSize));
   __ lw(a1, MemOperand(sp, 1 * kPointerSize));
-  __ Branch(loop_statement.break_target(), hs, a0, Operand(a1));
+  __ Branch(loop_statement.break_label(), hs, a0, Operand(a1));
 
   // Get the current entry of the array into register a3.
   __ lw(a2, MemOperand(sp, 2 * kPointerSize));
@@ -1053,7 +1020,7 @@
   __ push(a3);  // Current entry.
   __ InvokeBuiltin(Builtins::FILTER_KEY, CALL_FUNCTION);
   __ mov(a3, result_register());
-  __ Branch(loop_statement.continue_target(), eq, a3, Operand(zero_reg));
+  __ Branch(loop_statement.continue_label(), eq, a3, Operand(zero_reg));
 
   // Update the 'each' property or variable from the possibly filtered
   // entry in register a3.
@@ -1069,7 +1036,7 @@
 
   // Generate code for the going to the next element by incrementing
   // the index (smi) stored on top of the stack.
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   __ pop(a0);
   __ Addu(a0, a0, Operand(Smi::FromInt(1)));
   __ push(a0);
@@ -1078,7 +1045,7 @@
   __ Branch(&loop);
 
   // Remove the pointers stored on the stack.
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   __ Drop(5);
 
   // Exit and decrement the loop depth.
@@ -1533,9 +1500,7 @@
 
     // Update the write barrier for the array store with v0 as the scratch
     // register.
-    __ li(a2, Operand(offset));
-    // TODO(PJ): double check this RecordWrite call.
-    __ RecordWrite(a1, a2, result_register());
+    __ RecordWrite(a1, Operand(offset), a2, result_register());
 
     PrepareForBailoutForId(expr->GetIdForElement(i), NO_REGISTERS);
   }
@@ -2286,36 +2251,10 @@
       EmitCallWithIC(expr, key->handle(), RelocInfo::CODE_TARGET);
     } else {
       // Call to a keyed property.
-      // For a synthetic property use keyed load IC followed by function call,
-      // for a regular property use EmitKeyedCallWithIC.
-      if (prop->is_synthetic()) {
-        // Do not visit the object and key subexpressions (they are shared
-        // by all occurrences of the same rewritten parameter).
-        ASSERT(prop->obj()->AsVariableProxy() != NULL);
-        ASSERT(prop->obj()->AsVariableProxy()->var()->AsSlot() != NULL);
-        Slot* slot = prop->obj()->AsVariableProxy()->var()->AsSlot();
-        MemOperand operand = EmitSlotSearch(slot, a1);
-        __ lw(a1, operand);
-
-        ASSERT(prop->key()->AsLiteral() != NULL);
-        ASSERT(prop->key()->AsLiteral()->handle()->IsSmi());
-        __ li(a0, Operand(prop->key()->AsLiteral()->handle()));
-
-        // Record source code position for IC call.
-        SetSourcePosition(prop->position());
-
-        Handle<Code> ic = isolate()->builtins()->KeyedLoadIC_Initialize();
-        __ Call(ic, RelocInfo::CODE_TARGET, GetPropertyId(prop));
-        __ lw(a1, GlobalObjectOperand());
-        __ lw(a1, FieldMemOperand(a1, GlobalObject::kGlobalReceiverOffset));
-        __ Push(v0, a1);  // Function, receiver.
-        EmitCallWithStub(expr, NO_CALL_FUNCTION_FLAGS);
-      } else {
-        { PreservePositionScope scope(masm()->positions_recorder());
-          VisitForStackValue(prop->obj());
-        }
-        EmitKeyedCallWithIC(expr, prop->key());
+      { PreservePositionScope scope(masm()->positions_recorder());
+        VisitForStackValue(prop->obj());
       }
+      EmitKeyedCallWithIC(expr, prop->key());
     }
   } else {
     { PreservePositionScope scope(masm()->positions_recorder());
@@ -2761,7 +2700,7 @@
 
   // Objects with a non-function constructor have class 'Object'.
   __ bind(&non_function_constructor);
-  __ LoadRoot(v0, Heap::kfunction_class_symbolRootIndex);
+  __ LoadRoot(v0, Heap::kObject_symbolRootIndex);
   __ jmp(&done);
 
   // Non-JS objects have class null.
@@ -3602,39 +3541,6 @@
 }
 
 
-void FullCodeGenerator::EmitIsNativeOrStrictMode(ZoneList<Expression*>* args) {
-  ASSERT(args->length() == 1);
-
-  // Load the function into v0.
-  VisitForAccumulatorValue(args->at(0));
-
-  // Prepare for the test.
-  Label materialize_true, materialize_false;
-  Label* if_true = NULL;
-  Label* if_false = NULL;
-  Label* fall_through = NULL;
-  context()->PrepareTest(&materialize_true, &materialize_false,
-                         &if_true, &if_false, &fall_through);
-
-  // Test for strict mode function.
-  __ lw(a1, FieldMemOperand(v0, JSFunction::kSharedFunctionInfoOffset));
-  __ lw(a1, FieldMemOperand(a1, SharedFunctionInfo::kCompilerHintsOffset));
-  __ And(at, a1, Operand(1 << (SharedFunctionInfo::kStrictModeFunction +
-                               kSmiTagSize)));
-  __ Branch(if_true, ne, at, Operand(zero_reg));
-
-  // Test for native function.
-  __ And(at, a1, Operand(1 << (SharedFunctionInfo::kNative + kSmiTagSize)));
-  __ Branch(if_true, ne, at, Operand(zero_reg));
-
-  // Not native or strict-mode function.
-  __ Branch(if_false);
-
-  PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
-  context()->Plug(if_true, if_false);
-}
-
-
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   Handle<String> name = expr->name();
   if (name->length() > 0 && name->Get(0) == '_') {
@@ -3686,18 +3592,12 @@
       Variable* var = expr->expression()->AsVariableProxy()->AsVariable();
 
       if (prop != NULL) {
-        if (prop->is_synthetic()) {
-          // Result of deleting parameters is false, even when they rewrite
-          // to accesses on the arguments object.
-          context()->Plug(false);
-        } else {
-          VisitForStackValue(prop->obj());
-          VisitForStackValue(prop->key());
-          __ li(a1, Operand(Smi::FromInt(strict_mode_flag())));
-          __ push(a1);
-          __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
-          context()->Plug(v0);
-        }
+        VisitForStackValue(prop->obj());
+        VisitForStackValue(prop->key());
+        __ li(a1, Operand(Smi::FromInt(strict_mode_flag())));
+        __ push(a1);
+        __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
+        context()->Plug(v0);
       } else if (var != NULL) {
         // Delete of an unqualified identifier is disallowed in strict mode
         // but "delete this" is.
@@ -4052,6 +3952,10 @@
     __ Branch(if_true, eq, v0, Operand(at));
     __ LoadRoot(at, Heap::kFalseValueRootIndex);
     Split(eq, v0, Operand(at), if_true, if_false, fall_through);
+  } else if (FLAG_harmony_typeof &&
+             check->Equals(isolate()->heap()->null_symbol())) {
+    __ LoadRoot(at, Heap::kNullValueRootIndex);
+    Split(eq, v0, Operand(at), if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->undefined_symbol())) {
     __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
     __ Branch(if_true, eq, v0, Operand(at));
@@ -4069,8 +3973,10 @@
 
   } else if (check->Equals(isolate()->heap()->object_symbol())) {
     __ JumpIfSmi(v0, if_false);
-    __ LoadRoot(at, Heap::kNullValueRootIndex);
-    __ Branch(if_true, eq, v0, Operand(at));
+    if (!FLAG_harmony_typeof) {
+      __ LoadRoot(at, Heap::kNullValueRootIndex);
+      __ Branch(if_true, eq, v0, Operand(at));
+    }
     // Check for JS objects => true.
     __ GetObjectType(v0, v0, a1);
     __ Branch(if_false, lt, a1, Operand(FIRST_NONCALLABLE_SPEC_OBJECT_TYPE));
@@ -4313,6 +4219,34 @@
 
 #undef __
 
+#define __ ACCESS_MASM(masm())
+
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
+    int* stack_depth,
+    int* context_length) {
+  // The macros used here must preserve the result register.
+
+  // Because the handler block contains the context of the finally
+  // code, we can restore it directly from there for the finally code
+  // rather than iteratively unwinding contexts via their previous
+  // links.
+  __ Drop(*stack_depth);  // Down to the handler block.
+  if (*context_length > 0) {
+    // Restore the context to its dedicated register and the stack.
+    __ lw(cp, MemOperand(sp, StackHandlerConstants::kContextOffset));
+    __ sw(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
+  }
+  __ PopTryHandler();
+  __ Call(finally_entry_);
+
+  *stack_depth = 0;
+  *context_length = 0;
+  return previous_;
+}
+
+
+#undef __
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS
diff --git a/src/mips/ic-mips.cc b/src/mips/ic-mips.cc
index da39962..85cb916 100644
--- a/src/mips/ic-mips.cc
+++ b/src/mips/ic-mips.cc
@@ -885,8 +885,8 @@
   MemOperand unmapped_location =
       GenerateUnmappedArgumentsLookup(masm, a0, a2, a3, &slow);
   __ lw(a2, unmapped_location);
-  __ Branch(&slow, eq, a2, Operand(a3));
   __ LoadRoot(a3, Heap::kTheHoleValueRootIndex);
+  __ Branch(&slow, eq, a2, Operand(a3));
   __ mov(v0, a2);
   __ Ret();
   __ bind(&slow);
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 5e8d676..c7f727b 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -757,15 +757,20 @@
                          uint16_t pos,
                          uint16_t size) {
   ASSERT(pos < 32);
-  ASSERT(pos + size < 32);
+  ASSERT(pos + size < 33);
 
   if (mips32r2) {
     ext_(rt, rs, pos, size);
   } else {
     // Move rs to rt and shift it left then right to get the
     // desired bitfield on the right side and zeroes on the left.
-    sll(rt, rs, 32 - (pos + size));
-    srl(rt, rt, 32 - size);
+    int shift_left = 32 - (pos + size);
+    sll(rt, rs, shift_left);  // Acts as a move if shift_left == 0.
+
+    int shift_right = 32 - size;
+    if (shift_right > 0) {
+      srl(rt, rt, shift_right);
+    }
   }
 }
 
@@ -807,28 +812,32 @@
 }
 
 
-void MacroAssembler::Cvt_d_uw(FPURegister fd, FPURegister fs) {
-  // Move the data from fs to t4.
-  mfc1(t4, fs);
-  return Cvt_d_uw(fd, t4);
+void MacroAssembler::Cvt_d_uw(FPURegister fd,
+                              FPURegister fs,
+                              FPURegister scratch) {
+  // Move the data from fs to t8.
+  mfc1(t8, fs);
+  Cvt_d_uw(fd, t8, scratch);
 }
 
 
-void MacroAssembler::Cvt_d_uw(FPURegister fd, Register rs) {
+void MacroAssembler::Cvt_d_uw(FPURegister fd,
+                              Register rs,
+                              FPURegister scratch) {
   // Convert rs to a FP value in fd (and fd + 1).
   // We do this by converting rs minus the MSB to avoid sign conversion,
-  // then adding 2^31-1 and 1 to the result.
+  // then adding 2^31 to the result (if needed).
 
-  ASSERT(!fd.is(f20));
+  ASSERT(!fd.is(scratch));
   ASSERT(!rs.is(t9));
-  ASSERT(!rs.is(t8));
+  ASSERT(!rs.is(at));
 
-  // Save rs's MSB to t8.
-  And(t8, rs, 0x80000000);
+  // Save rs's MSB to t9.
+  Ext(t9, rs, 31, 1);
   // Remove rs's MSB.
-  And(t9, rs, 0x7FFFFFFF);
-  // Move t9 to fd.
-  mtc1(t9, fd);
+  Ext(at, rs, 0, 31);
+  // Move the result to fd.
+  mtc1(at, fd);
 
   // Convert fd to a real FP value.
   cvt_d_w(fd, fd);
@@ -837,41 +846,39 @@
 
   // If rs's MSB was 0, it's done.
   // Otherwise we need to add that to the FP register.
-  Branch(&conversion_done, eq, t8, Operand(zero_reg));
+  Branch(&conversion_done, eq, t9, Operand(zero_reg));
 
-  // First load 2^31 - 1 into f20.
-  Or(t9, zero_reg, 0x7FFFFFFF);
-  mtc1(t9, f20);
+  // Load 2^31 into f20 as its float representation.
+  li(at, 0x41E00000);
+  mtc1(at, FPURegister::from_code(scratch.code() + 1));
+  mtc1(zero_reg, scratch);
+  // Add it to fd.
+  add_d(fd, fd, scratch);
 
-  // Convert it to FP and add it to fd.
-  cvt_d_w(f20, f20);
-  add_d(fd, fd, f20);
-  // Now add 1.
-  Or(t9, zero_reg, 1);
-  mtc1(t9, f20);
-
-  cvt_d_w(f20, f20);
-  add_d(fd, fd, f20);
   bind(&conversion_done);
 }
 
 
-void MacroAssembler::Trunc_uw_d(FPURegister fd, FPURegister fs) {
-  Trunc_uw_d(fs, t4);
-  mtc1(t4, fd);
+void MacroAssembler::Trunc_uw_d(FPURegister fd,
+                                FPURegister fs,
+                                FPURegister scratch) {
+  Trunc_uw_d(fs, t8, scratch);
+  mtc1(t8, fd);
 }
 
 
-void MacroAssembler::Trunc_uw_d(FPURegister fd, Register rs) {
-  ASSERT(!fd.is(f22));
-  ASSERT(!rs.is(t8));
+void MacroAssembler::Trunc_uw_d(FPURegister fd,
+                                Register rs,
+                                FPURegister scratch) {
+  ASSERT(!fd.is(scratch));
+  ASSERT(!rs.is(at));
 
-  // Load 2^31 into f22.
-  Or(t8, zero_reg, 0x80000000);
-  Cvt_d_uw(f22, t8);
-
-  // Test if f22 > fd.
-  c(OLT, D, fd, f22);
+  // Load 2^31 into scratch as its float representation.
+  li(at, 0x41E00000);
+  mtc1(at, FPURegister::from_code(scratch.code() + 1));
+  mtc1(zero_reg, scratch);
+  // Test if scratch > fd.
+  c(OLT, D, fd, scratch);
 
   Label simple_convert;
   // If fd < 2^31 we can convert it normally.
@@ -879,18 +886,17 @@
 
   // First we subtract 2^31 from fd, then trunc it to rs
   // and add 2^31 to rs.
-
-  sub_d(f22, fd, f22);
-  trunc_w_d(f22, f22);
-  mfc1(rs, f22);
-  or_(rs, rs, t8);
+  sub_d(scratch, fd, scratch);
+  trunc_w_d(scratch, scratch);
+  mfc1(rs, scratch);
+  Or(rs, rs, 1 << 31);
 
   Label done;
   Branch(&done);
   // Simple conversion.
   bind(&simple_convert);
-  trunc_w_d(f22, fd);
-  mfc1(rs, f22);
+  trunc_w_d(scratch, fd);
+  mfc1(rs, scratch);
 
   bind(&done);
 }
@@ -1551,12 +1557,14 @@
         b(offset);
         break;
       case eq:
+        ASSERT(!scratch.is(rs));
         r2 = scratch;
         li(r2, rt);
         offset = shifted_branch_offset(L, false);
         beq(rs, r2, offset);
         break;
       case ne:
+        ASSERT(!scratch.is(rs));
         r2 = scratch;
         li(r2, rt);
         offset = shifted_branch_offset(L, false);
@@ -1568,6 +1576,7 @@
           offset = shifted_branch_offset(L, false);
           bgtz(rs, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           slt(scratch, r2, rs);
@@ -1584,6 +1593,7 @@
           offset = shifted_branch_offset(L, false);
           beq(scratch, zero_reg, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           slt(scratch, rs, r2);
@@ -1600,6 +1610,7 @@
           offset = shifted_branch_offset(L, false);
           bne(scratch, zero_reg, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           slt(scratch, rs, r2);
@@ -1612,6 +1623,7 @@
           offset = shifted_branch_offset(L, false);
           blez(rs, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           slt(scratch, r2, rs);
@@ -1625,6 +1637,7 @@
           offset = shifted_branch_offset(L, false);
           bgtz(rs, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           sltu(scratch, r2, rs);
@@ -1641,6 +1654,7 @@
           offset = shifted_branch_offset(L, false);
           beq(scratch, zero_reg, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           sltu(scratch, rs, r2);
@@ -1657,6 +1671,7 @@
           offset = shifted_branch_offset(L, false);
           bne(scratch, zero_reg, offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           sltu(scratch, rs, r2);
@@ -1669,6 +1684,7 @@
           offset = shifted_branch_offset(L, false);
           b(offset);
         } else {
+          ASSERT(!scratch.is(rs));
           r2 = scratch;
           li(r2, rt);
           sltu(scratch, r2, rs);
@@ -2244,7 +2260,13 @@
 void MacroAssembler::PushTryHandler(CodeLocation try_location,
                                     HandlerType type) {
   // Adjust this code if not the case.
-  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
+
   // The return address is passed in register ra.
   if (try_location == IN_JAVASCRIPT) {
     if (type == TRY_CATCH_HANDLER) {
@@ -2252,19 +2274,16 @@
     } else {
       li(t0, Operand(StackHandler::TRY_FINALLY));
     }
-    ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize
-           && StackHandlerConstants::kFPOffset == 2 * kPointerSize
-           && StackHandlerConstants::kPCOffset == 3 * kPointerSize
-           && StackHandlerConstants::kNextOffset == 0 * kPointerSize);
     // Save the current handler as the next handler.
     li(t2, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
     lw(t1, MemOperand(t2));
 
     addiu(sp, sp, -StackHandlerConstants::kSize);
-    sw(ra, MemOperand(sp, 12));
-    sw(fp, MemOperand(sp, 8));
-    sw(t0, MemOperand(sp, 4));
-    sw(t1, MemOperand(sp, 0));
+    sw(ra, MemOperand(sp, StackHandlerConstants::kPCOffset));
+    sw(fp, MemOperand(sp, StackHandlerConstants::kFPOffset));
+    sw(cp, MemOperand(sp, StackHandlerConstants::kContextOffset));
+    sw(t0, MemOperand(sp, StackHandlerConstants::kStateOffset));
+    sw(t1, MemOperand(sp, StackHandlerConstants::kNextOffset));
 
     // Link this handler as the new current one.
     sw(sp, MemOperand(t2));
@@ -2272,11 +2291,6 @@
   } else {
     // Must preserve a0-a3, and s0 (argv).
     ASSERT(try_location == IN_JS_ENTRY);
-    ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize
-           && StackHandlerConstants::kFPOffset == 2 * kPointerSize
-           && StackHandlerConstants::kPCOffset == 3 * kPointerSize
-           && StackHandlerConstants::kNextOffset == 0 * kPointerSize);
-
     // The frame pointer does not point to a JS frame so we save NULL
     // for fp. We expect the code throwing an exception to check fp
     // before dereferencing it to restore the context.
@@ -2286,11 +2300,14 @@
     li(t2, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
     lw(t1, MemOperand(t2));
 
+    ASSERT(Smi::FromInt(0) == 0);  // Used for no context.
+
     addiu(sp, sp, -StackHandlerConstants::kSize);
-    sw(ra, MemOperand(sp, 12));
-    sw(zero_reg, MemOperand(sp, 8));
-    sw(t0, MemOperand(sp, 4));
-    sw(t1, MemOperand(sp, 0));
+    sw(ra, MemOperand(sp, StackHandlerConstants::kPCOffset));
+    sw(zero_reg, MemOperand(sp, StackHandlerConstants::kFPOffset));
+    sw(zero_reg, MemOperand(sp, StackHandlerConstants::kContextOffset));
+    sw(t0, MemOperand(sp, StackHandlerConstants::kStateOffset));
+    sw(t1, MemOperand(sp, StackHandlerConstants::kNextOffset));
 
     // Link this handler as the new current one.
     sw(sp, MemOperand(t2));
@@ -2299,7 +2316,7 @@
 
 
 void MacroAssembler::PopTryHandler() {
-  ASSERT_EQ(0, StackHandlerConstants::kNextOffset);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(a1);
   Addu(sp, sp, Operand(StackHandlerConstants::kSize - kPointerSize));
   li(at, Operand(ExternalReference(Isolate::k_handler_address, isolate())));
@@ -2312,28 +2329,31 @@
   Move(v0, value);
 
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
 
   // Drop the sp to the top of the handler.
   li(a3, Operand(ExternalReference(Isolate::k_handler_address,
-                                      isolate())));
+                                   isolate())));
   lw(sp, MemOperand(a3));
 
-  // Restore the next handler and frame pointer, discard handler state.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  // Restore the next handler.
   pop(a2);
   sw(a2, MemOperand(a3));
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
-  MultiPop(a3.bit() | fp.bit());
 
-  // Before returning we restore the context from the frame pointer if
-  // not NULL.  The frame pointer is NULL in the exception handler of a
-  // JS entry frame.
-  // Set cp to NULL if fp is NULL.
+  // Restore context and frame pointer, discard state (a3).
+  MultiPop(a3.bit() | cp.bit() | fp.bit());
+
+  // If the handler is a JS frame, restore the context to the frame.
+  // (a3 == ENTRY) == (fp == 0) == (cp == 0), so we could test any
+  // of them.
   Label done;
-  Branch(USE_DELAY_SLOT, &done, eq, fp, Operand(zero_reg));
-  mov(cp, zero_reg);   // In branch delay slot.
-  lw(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
+  Branch(&done, eq, fp, Operand(zero_reg));
+  sw(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
   bind(&done);
 
 #ifdef DEBUG
@@ -2355,7 +2375,6 @@
   }
 #endif
 
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   pop(t9);  // 2 instructions: lw, add sp.
   Jump(t9);  // 2 instructions: jr, nop (in delay slot).
 
@@ -2370,7 +2389,12 @@
 void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
                                       Register value) {
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
 
   // v0 is expected to hold the exception.
   Move(v0, value);
@@ -2393,7 +2417,6 @@
   bind(&done);
 
   // Set the top handler address to next handler past the current ENTRY handler.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(a2);
   sw(a2, MemOperand(a3));
 
@@ -2415,20 +2438,12 @@
 
   // Stack layout at this point. See also StackHandlerConstants.
   // sp ->   state (ENTRY)
+  //         cp
   //         fp
   //         ra
 
-  // Discard handler state (a2 is not used) and restore frame pointer.
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
-  MultiPop(a2.bit() | fp.bit());  // a2: discarded state.
-  // Before returning we restore the context from the frame pointer if
-  // not NULL.  The frame pointer is NULL in the exception handler of a
-  // JS entry frame.
-  Label cp_null;
-  Branch(USE_DELAY_SLOT, &cp_null, eq, fp, Operand(zero_reg));
-  mov(cp, zero_reg);   // In the branch delay slot.
-  lw(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
-  bind(&cp_null);
+  // Restore context and frame pointer, discard state (r2).
+  MultiPop(a2.bit() | cp.bit() | fp.bit());
 
 #ifdef DEBUG
   // When emitting debug_code, set ra as return address for the jump.
@@ -2448,7 +2463,6 @@
     addiu(ra, ra, kOffsetRaBytes);
   }
 #endif
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   pop(t9);  // 2 instructions: lw, add sp.
   Jump(t9);  // 2 instructions: jr, nop (in delay slot).
 
diff --git a/src/mips/macro-assembler-mips.h b/src/mips/macro-assembler-mips.h
index 4994516..0fcf6f1 100644
--- a/src/mips/macro-assembler-mips.h
+++ b/src/mips/macro-assembler-mips.h
@@ -524,12 +524,12 @@
   void Ext(Register rt, Register rs, uint16_t pos, uint16_t size);
 
   // Convert unsigned word to double.
-  void Cvt_d_uw(FPURegister fd, FPURegister fs);
-  void Cvt_d_uw(FPURegister fd, Register rs);
+  void Cvt_d_uw(FPURegister fd, FPURegister fs, FPURegister scratch);
+  void Cvt_d_uw(FPURegister fd, Register rs, FPURegister scratch);
 
   // Convert double to unsigned word.
-  void Trunc_uw_d(FPURegister fd, FPURegister fs);
-  void Trunc_uw_d(FPURegister fd, Register rs);
+  void Trunc_uw_d(FPURegister fd, FPURegister fs, FPURegister scratch);
+  void Trunc_uw_d(FPURegister fd, Register rs, FPURegister scratch);
 
   // Convert the HeapNumber pointed to by source to a 32bits signed integer
   // dest. If the HeapNumber does not fit into a 32bits signed integer branch
diff --git a/src/mips/regexp-macro-assembler-mips.cc b/src/mips/regexp-macro-assembler-mips.cc
index 9935ef9..63e836f 100644
--- a/src/mips/regexp-macro-assembler-mips.cc
+++ b/src/mips/regexp-macro-assembler-mips.cc
@@ -1036,12 +1036,12 @@
   }
 
   // Prepare for possible GC.
-  HandleScope handles;
+  HandleScope handles(isolate);
   Handle<Code> code_handle(re_code);
 
   Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
   // Current string.
-  bool is_ascii = subject->IsAsciiRepresentation();
+  bool is_ascii = subject->IsAsciiRepresentationUnderneath();
 
   ASSERT(re_code->instruction_start() <= *return_address);
   ASSERT(*return_address <=
@@ -1050,7 +1050,7 @@
   MaybeObject* result = Execution::HandleStackGuardInterrupt();
 
   if (*code_handle != re_code) {  // Return address no longer valid.
-    int delta = *code_handle - re_code;
+    int delta = code_handle->address() - re_code->address();
     // Overwrite the return address on the stack.
     *return_address += delta;
   }
@@ -1059,8 +1059,20 @@
     return EXCEPTION;
   }
 
+  Handle<String> subject_tmp = subject;
+  int slice_offset = 0;
+
+  // Extract the underlying string and the slice offset.
+  if (StringShape(*subject_tmp).IsCons()) {
+    subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
+  } else if (StringShape(*subject_tmp).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(*subject_tmp);
+    subject_tmp = Handle<String>(slice->parent());
+    slice_offset = slice->offset();
+  }
+
   // String might have changed.
-  if (subject->IsAsciiRepresentation() != is_ascii) {
+  if (subject_tmp->IsAsciiRepresentation() != is_ascii) {
     // If we changed between an ASCII and an UC16 string, the specialized
     // code cannot be used, and we need to restart regexp matching from
     // scratch (including, potentially, compiling a new version of the code).
@@ -1071,8 +1083,8 @@
   // be a sequential or external string with the same content.
   // Update the start and end pointers in the stack frame to the current
   // location (whether it has actually moved or not).
-  ASSERT(StringShape(*subject).IsSequential() ||
-      StringShape(*subject).IsExternal());
+  ASSERT(StringShape(*subject_tmp).IsSequential() ||
+      StringShape(*subject_tmp).IsExternal());
 
   // The original start address of the characters to match.
   const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);
@@ -1080,13 +1092,14 @@
   // Find the current start address of the same character at the current string
   // position.
   int start_index = frame_entry<int>(re_frame, kStartIndex);
-  const byte* new_address = StringCharacterPosition(*subject, start_index);
+  const byte* new_address = StringCharacterPosition(*subject_tmp,
+                                                    start_index + slice_offset);
 
   if (start_address != new_address) {
     // If there is a difference, update the object pointer and start and end
     // addresses in the RegExp stack frame to match the new value.
     const byte* end_address = frame_entry<const byte* >(re_frame, kInputEnd);
-    int byte_length = end_address - start_address;
+    int byte_length = static_cast<int>(end_address - start_address);
     frame_entry<const String*>(re_frame, kInputString) = *subject;
     frame_entry<const byte*>(re_frame, kInputStart) = new_address;
     frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
diff --git a/src/mips/simulator-mips.cc b/src/mips/simulator-mips.cc
index 30e12e7..3b38695 100644
--- a/src/mips/simulator-mips.cc
+++ b/src/mips/simulator-mips.cc
@@ -1409,20 +1409,11 @@
     int32_t arg1 = get_register(a1);
     int32_t arg2 = get_register(a2);
     int32_t arg3 = get_register(a3);
-    int32_t arg4 = 0;
-    int32_t arg5 = 0;
 
-    // Need to check if sp is valid before assigning arg4, arg5.
-    // This is a fix for cctest test-api/CatchStackOverflow which causes
-    // the stack to overflow. For some reason arm doesn't need this
-    // stack check here.
     int32_t* stack_pointer = reinterpret_cast<int32_t*>(get_register(sp));
-    int32_t* stack = reinterpret_cast<int32_t*>(stack_);
-    if (stack_pointer >= stack && stack_pointer < stack + stack_size_ - 5) {
-      // Args 4 and 5 are on the stack after the reserved space for args 0..3.
-      arg4 = stack_pointer[4];
-      arg5 = stack_pointer[5];
-    }
+    // Args 4 and 5 are on the stack after the reserved space for args 0..3.
+    int32_t arg4 = stack_pointer[4];
+    int32_t arg5 = stack_pointer[5];
 
     bool fp_call =
          (redirection->type() == ExternalReference::BUILTIN_FP_FP_CALL) ||
diff --git a/src/mips/stub-cache-mips.cc b/src/mips/stub-cache-mips.cc
index f1ffe9b..c17a658 100644
--- a/src/mips/stub-cache-mips.cc
+++ b/src/mips/stub-cache-mips.cc
@@ -3494,7 +3494,7 @@
   __ lw(t1, FieldMemOperand(a3, ExternalArray::kLengthOffset));
   __ sra(t2, key, kSmiTagSize);
   // Unsigned comparison catches both negative and too-large values.
-  __ Branch(&miss_force_generic, Uless, t1, Operand(t2));
+  __ Branch(&miss_force_generic, Ugreater_equal, key, Operand(t1));
 
   __ lw(a3, FieldMemOperand(a3, ExternalArray::kExternalPointerOffset));
   // a3: base pointer of external storage
@@ -3638,7 +3638,7 @@
       // __ mtc1(zero_reg, f1);  // MS 32-bits are all zero.
       // __ cvt_d_l(f0, f0); // Use 64 bit conv to get correct unsigned 32-bit.
 
-      __ Cvt_d_uw(f0, value);
+      __ Cvt_d_uw(f0, value, f22);
 
       __ sdc1(f0, MemOperand(v0, HeapNumber::kValueOffset - kHeapObjectTag));
 
@@ -3822,16 +3822,16 @@
   // This stub is meant to be tail-jumped to, the receiver must already
   // have been verified by the caller to not be a smi.
 
-  __ lw(a3, FieldMemOperand(receiver, JSObject::kElementsOffset));
-
-  // Check that the key is a smi.
+    // Check that the key is a smi.
   __ JumpIfNotSmi(key, &miss_force_generic);
 
+  __ lw(a3, FieldMemOperand(receiver, JSObject::kElementsOffset));
+
   // Check that the index is in range.
   __ SmiUntag(t0, key);
   __ lw(t1, FieldMemOperand(a3, ExternalArray::kLengthOffset));
   // Unsigned comparison catches both negative and too-large values.
-  __ Branch(&miss_force_generic, Ugreater_equal, t0, Operand(t1));
+  __ Branch(&miss_force_generic, Ugreater_equal, key, Operand(t1));
 
   // Handle both smis and HeapNumbers in the fast path. Go to the
   // runtime for all other kinds of values.
@@ -4428,7 +4428,8 @@
   __ sw(mantissa_reg, FieldMemOperand(scratch, FixedDoubleArray::kHeaderSize));
   uint32_t offset = FixedDoubleArray::kHeaderSize + sizeof(kHoleNanLower32);
   __ sw(exponent_reg, FieldMemOperand(scratch, offset));
-  __ Ret();
+  __ Ret(USE_DELAY_SLOT);
+  __ mov(v0, value_reg);  // In delay slot.
 
   __ bind(&maybe_nan);
   // Could be NaN or Infinity. If fraction is not zero, it's NaN, otherwise
@@ -4459,11 +4460,18 @@
   } else {
     destination = FloatingPointHelper::kCoreRegisters;
   }
-  __ SmiUntag(value_reg, value_reg);
+
+  Register untagged_value = receiver_reg;
+  __ SmiUntag(untagged_value, value_reg);
   FloatingPointHelper::ConvertIntToDouble(
-      masm, value_reg, destination,
-      f0, mantissa_reg, exponent_reg,  // These are: double_dst, dst1, dst2.
-      scratch4, f2);  // These are: scratch2, single_scratch.
+      masm,
+      untagged_value,
+      destination,
+      f0,
+      mantissa_reg,
+      exponent_reg,
+      scratch4,
+      f2);
   if (destination == FloatingPointHelper::kFPURegisters) {
     CpuFeatures::Scope scope(FPU);
     __ sdc1(f0, MemOperand(scratch, 0));
@@ -4471,7 +4479,8 @@
     __ sw(mantissa_reg, MemOperand(scratch, 0));
     __ sw(exponent_reg, MemOperand(scratch, Register::kSizeInBytes));
   }
-  __ Ret();
+  __ Ret(USE_DELAY_SLOT);
+  __ mov(v0, value_reg);  // In delay slot.
 
   // Handle store cache miss, replacing the ic with the generic stub.
   __ bind(&miss_force_generic);
diff --git a/src/mirror-debugger.js b/src/mirror-debugger.js
index bad0800..e3f3c48 100644
--- a/src/mirror-debugger.js
+++ b/src/mirror-debugger.js
@@ -195,7 +195,8 @@
               Local: 1,
               With: 2,
               Closure: 3,
-              Catch: 4 };
+              Catch: 4,
+              Block: 5 };
 
 
 // Mirror hierarchy:
diff --git a/src/mksnapshot.cc b/src/mksnapshot.cc
index c5ce12f..4f5fe96 100644
--- a/src/mksnapshot.cc
+++ b/src/mksnapshot.cc
@@ -40,8 +40,6 @@
 #include "serialize.h"
 #include "list.h"
 
-// use explicit namespace to avoid clashing with types in namespace v8
-namespace i = v8::internal;
 using namespace v8;
 
 static const unsigned int kMaxCounters = 256;
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index 2963231..4da360b 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -153,6 +153,9 @@
     case JS_ARRAY_TYPE:
       JSArray::cast(this)->JSArrayVerify();
       break;
+    case JS_WEAK_MAP_TYPE:
+      JSWeakMap::cast(this)->JSWeakMapVerify();
+      break;
     case JS_REGEXP_TYPE:
       JSRegExp::cast(this)->JSRegExpVerify();
       break;
@@ -313,7 +316,7 @@
 void FixedDoubleArray::FixedDoubleArrayVerify() {
   for (int i = 0; i < length(); i++) {
     if (!is_the_hole(i)) {
-      double value = get(i);
+      double value = get_scalar(i);
       ASSERT(!isnan(value) ||
              (BitCast<uint64_t>(value) ==
               BitCast<uint64_t>(canonical_not_the_hole_nan_as_double())));
@@ -349,6 +352,31 @@
   if (IsSymbol()) {
     CHECK(!HEAP->InNewSpace(this));
   }
+  if (IsConsString()) {
+    ConsString::cast(this)->ConsStringVerify();
+  } else if (IsSlicedString()) {
+    SlicedString::cast(this)->SlicedStringVerify();
+  }
+}
+
+
+void ConsString::ConsStringVerify() {
+  CHECK(this->first()->IsString());
+  CHECK(this->second() == GetHeap()->empty_string() ||
+        this->second()->IsString());
+  CHECK(this->length() >= String::kMinNonFlatLength);
+  if (this->IsFlat()) {
+    // A flat cons can only be created by String::SlowTryFlatten.
+    // Afterwards, the first part may be externalized.
+    CHECK(this->first()->IsSeqString() || this->first()->IsExternalString());
+  }
+}
+
+
+void SlicedString::SlicedStringVerify() {
+  CHECK(!this->parent()->IsConsString());
+  CHECK(!this->parent()->IsSlicedString());
+  CHECK(this->length() >= SlicedString::kMinLength);
 }
 
 
@@ -453,6 +481,14 @@
 }
 
 
+void JSWeakMap::JSWeakMapVerify() {
+  CHECK(IsJSWeakMap());
+  JSObjectVerify();
+  VerifyHeapPointer(table());
+  ASSERT(table()->IsHashTable());
+}
+
+
 void JSRegExp::JSRegExpVerify() {
   JSObjectVerify();
   ASSERT(data()->IsUndefined() || data()->IsFixedArray());
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 70f6267..ff3be03 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -35,6 +35,7 @@
 #ifndef V8_OBJECTS_INL_H_
 #define V8_OBJECTS_INL_H_
 
+#include "elements.h"
 #include "objects.h"
 #include "contexts.h"
 #include "conversions-inl.h"
@@ -158,23 +159,33 @@
 }
 
 
+bool Object::IsSpecObject() {
+  return Object::IsHeapObject()
+    && HeapObject::cast(this)->map()->instance_type() >= FIRST_SPEC_OBJECT_TYPE;
+}
+
+
 bool Object::IsSymbol() {
   if (!this->IsHeapObject()) return false;
   uint32_t type = HeapObject::cast(this)->map()->instance_type();
   // Because the symbol tag is non-zero and no non-string types have the
   // symbol bit set we can test for symbols with a very simple test
   // operation.
-  ASSERT(kSymbolTag != 0);
+  STATIC_ASSERT(kSymbolTag != 0);
   ASSERT(kNotStringTag + kIsSymbolMask > LAST_TYPE);
   return (type & kIsSymbolMask) != 0;
 }
 
 
 bool Object::IsConsString() {
-  if (!this->IsHeapObject()) return false;
-  uint32_t type = HeapObject::cast(this)->map()->instance_type();
-  return (type & (kIsNotStringMask | kStringRepresentationMask)) ==
-         (kStringTag | kConsStringTag);
+  if (!IsString()) return false;
+  return StringShape(String::cast(this)).IsCons();
+}
+
+
+bool Object::IsSlicedString() {
+  if (!IsString()) return false;
+  return StringShape(String::cast(this)).IsSliced();
 }
 
 
@@ -245,7 +256,7 @@
 
 bool StringShape::IsSymbol() {
   ASSERT(valid());
-  ASSERT(kSymbolTag != 0);
+  STATIC_ASSERT(kSymbolTag != 0);
   return (type_ & kIsSymbolMask) != 0;
 }
 
@@ -262,6 +273,38 @@
 }
 
 
+bool String::IsAsciiRepresentationUnderneath() {
+  uint32_t type = map()->instance_type();
+  STATIC_ASSERT(kIsIndirectStringTag != 0);
+  STATIC_ASSERT((kIsIndirectStringMask & kStringEncodingMask) == 0);
+  ASSERT(IsFlat());
+  switch (type & (kIsIndirectStringMask | kStringEncodingMask)) {
+    case kAsciiStringTag:
+      return true;
+    case kTwoByteStringTag:
+      return false;
+    default:  // Cons or sliced string.  Need to go deeper.
+      return GetUnderlying()->IsAsciiRepresentation();
+  }
+}
+
+
+bool String::IsTwoByteRepresentationUnderneath() {
+  uint32_t type = map()->instance_type();
+  STATIC_ASSERT(kIsIndirectStringTag != 0);
+  STATIC_ASSERT((kIsIndirectStringMask & kStringEncodingMask) == 0);
+  ASSERT(IsFlat());
+  switch (type & (kIsIndirectStringMask | kStringEncodingMask)) {
+    case kAsciiStringTag:
+      return false;
+    case kTwoByteStringTag:
+      return true;
+    default:  // Cons or sliced string.  Need to go deeper.
+      return GetUnderlying()->IsTwoByteRepresentation();
+  }
+}
+
+
 bool String::HasOnlyAsciiChars() {
   uint32_t type = map()->instance_type();
   return (type & kStringEncodingMask) == kAsciiStringTag ||
@@ -274,6 +317,16 @@
 }
 
 
+bool StringShape::IsSliced() {
+  return (type_ & kStringRepresentationMask) == kSlicedStringTag;
+}
+
+
+bool StringShape::IsIndirect() {
+  return (type_ & kIsIndirectStringMask) == kIsIndirectStringTag;
+}
+
+
 bool StringShape::IsExternal() {
   return (type_ & kStringRepresentationMask) == kExternalStringTag;
 }
@@ -290,6 +343,11 @@
 }
 
 
+uint32_t StringShape::encoding_tag() {
+  return type_ & kStringEncodingMask;
+}
+
+
 uint32_t StringShape::full_representation_tag() {
   return (type_ & (kStringRepresentationMask | kStringEncodingMask));
 }
@@ -474,6 +532,12 @@
 }
 
 
+bool Object::IsJSWeakMap() {
+  return Object::IsJSObject() &&
+      HeapObject::cast(this)->map()->instance_type() == JS_WEAK_MAP_TYPE;
+}
+
+
 bool Object::IsJSContextExtensionObject() {
   return IsHeapObject()
       && (HeapObject::cast(this)->map()->instance_type() ==
@@ -539,7 +603,8 @@
     return (map == heap->function_context_map() ||
             map == heap->catch_context_map() ||
             map == heap->with_context_map() ||
-            map == heap->global_context_map());
+            map == heap->global_context_map() ||
+            map == heap->block_context_map());
   }
   return false;
 }
@@ -552,6 +617,13 @@
 }
 
 
+bool Object::IsSerializedScopeInfo() {
+  return Object::IsHeapObject() &&
+      HeapObject::cast(this)->map() ==
+      HeapObject::cast(this)->GetHeap()->serialized_scope_info_map();
+}
+
+
 bool Object::IsJSFunction() {
   return Object::IsHeapObject()
       && HeapObject::cast(this)->map()->instance_type() == JS_FUNCTION_TYPE;
@@ -1322,17 +1394,19 @@
 ACCESSORS(JSObject, properties, FixedArray, kPropertiesOffset)
 
 
-HeapObject* JSObject::elements() {
+FixedArrayBase* JSObject::elements() {
   Object* array = READ_FIELD(this, kElementsOffset);
   ASSERT(array->HasValidElements());
-  return reinterpret_cast<HeapObject*>(array);
+  return static_cast<FixedArrayBase*>(array);
 }
 
 
-void JSObject::set_elements(HeapObject* value, WriteBarrierMode mode) {
+void JSObject::set_elements(FixedArrayBase* value, WriteBarrierMode mode) {
   ASSERT(map()->has_fast_elements() ==
          (value->map() == GetHeap()->fixed_array_map() ||
           value->map() == GetHeap()->fixed_cow_array_map()));
+  ASSERT(map()->has_fast_double_elements() ==
+         value->IsFixedDoubleArray());
   ASSERT(value->HasValidElements());
   WRITE_FIELD(this, kElementsOffset, value);
   CONDITIONAL_WRITE_BARRIER(GetHeap(), this, kElementsOffset, mode);
@@ -1408,6 +1482,8 @@
       return JSValue::kSize;
     case JS_ARRAY_TYPE:
       return JSValue::kSize;
+    case JS_WEAK_MAP_TYPE:
+      return JSWeakMap::kSize;
     case JS_REGEXP_TYPE:
       return JSValue::kSize;
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
@@ -1595,6 +1671,7 @@
 
 void FixedArray::set(int index, Smi* value) {
   ASSERT(map() != HEAP->fixed_cow_array_map());
+  ASSERT(index >= 0 && index < this->length());
   ASSERT(reinterpret_cast<Object*>(value)->IsSmi());
   int offset = kHeaderSize + index * kPointerSize;
   WRITE_FIELD(this, offset, value);
@@ -1627,7 +1704,7 @@
 }
 
 
-double FixedDoubleArray::get(int index) {
+double FixedDoubleArray::get_scalar(int index) {
   ASSERT(map() != HEAP->fixed_cow_array_map() &&
          map() != HEAP->fixed_array_map());
   ASSERT(index >= 0 && index < this->length());
@@ -1637,6 +1714,15 @@
 }
 
 
+MaybeObject* FixedDoubleArray::get(int index) {
+  if (is_the_hole(index)) {
+    return GetHeap()->the_hole_value();
+  } else {
+    return GetHeap()->NumberFromDouble(get_scalar(index));
+  }
+}
+
+
 void FixedDoubleArray::set(int index, double value) {
   ASSERT(map() != HEAP->fixed_cow_array_map() &&
          map() != HEAP->fixed_array_map());
@@ -1663,9 +1749,19 @@
 void FixedDoubleArray::Initialize(FixedDoubleArray* from) {
   int old_length = from->length();
   ASSERT(old_length < length());
-  OS::MemCopy(FIELD_ADDR(this, kHeaderSize),
-              FIELD_ADDR(from, kHeaderSize),
-              old_length * kDoubleSize);
+  if (old_length * kDoubleSize >= OS::kMinComplexMemCopy) {
+    OS::MemCopy(FIELD_ADDR(this, kHeaderSize),
+                FIELD_ADDR(from, kHeaderSize),
+                old_length * kDoubleSize);
+  } else {
+    for (int i = 0; i < old_length; ++i) {
+      if (from->is_the_hole(i)) {
+        set_the_hole(i);
+      } else {
+        set(i, from->get_scalar(i));
+      }
+    }
+  }
   int offset = kHeaderSize + old_length * kDoubleSize;
   for (int current = from->length(); current < length(); ++current) {
     WRITE_DOUBLE_FIELD(this, offset, hole_nan_as_double());
@@ -1961,6 +2057,17 @@
 
 
 template<typename Shape, typename Key>
+int HashTable<Shape, Key>::ComputeCapacity(int at_least_space_for) {
+  const int kMinCapacity = 32;
+  int capacity = RoundUpToPowerOf2(at_least_space_for * 2);
+  if (capacity < kMinCapacity) {
+    capacity = kMinCapacity;  // Guarantee min capacity.
+  }
+  return capacity;
+}
+
+
+template<typename Shape, typename Key>
 int HashTable<Shape, Key>::FindEntry(Key key) {
   return FindEntry(GetIsolate(), key);
 }
@@ -2024,6 +2131,7 @@
 CAST_ACCESSOR(SeqString)
 CAST_ACCESSOR(SeqAsciiString)
 CAST_ACCESSOR(SeqTwoByteString)
+CAST_ACCESSOR(SlicedString)
 CAST_ACCESSOR(ConsString)
 CAST_ACCESSOR(ExternalString)
 CAST_ACCESSOR(ExternalAsciiString)
@@ -2047,6 +2155,7 @@
 CAST_ACCESSOR(JSRegExp)
 CAST_ACCESSOR(JSProxy)
 CAST_ACCESSOR(JSFunctionProxy)
+CAST_ACCESSOR(JSWeakMap)
 CAST_ACCESSOR(Foreign)
 CAST_ACCESSOR(ByteArray)
 CAST_ACCESSOR(ExternalArray)
@@ -2075,12 +2184,6 @@
 
 
 SMI_ACCESSORS(FixedArrayBase, length, kLengthOffset)
-SMI_ACCESSORS(ByteArray, length, kLengthOffset)
-
-// TODO(1493): Investigate if it's possible to s/INT/SMI/ here (and
-// subsequently unify H{Fixed,External}ArrayLength).
-INT_ACCESSORS(ExternalArray, length, kLengthOffset)
-
 
 SMI_ACCESSORS(String, length, kLengthOffset)
 
@@ -2110,7 +2213,7 @@
 MaybeObject* String::TryFlatten(PretenureFlag pretenure) {
   if (!StringShape(this).IsCons()) return this;
   ConsString* cons = ConsString::cast(this);
-  if (cons->second()->length() == 0) return cons->first();
+  if (cons->IsFlat()) return cons->first();
   return SlowTryFlatten(pretenure);
 }
 
@@ -2118,10 +2221,8 @@
 String* String::TryFlattenGetString(PretenureFlag pretenure) {
   MaybeObject* flat = TryFlatten(pretenure);
   Object* successfully_flattened;
-  if (flat->ToObject(&successfully_flattened)) {
-    return String::cast(successfully_flattened);
-  }
-  return this;
+  if (!flat->ToObject(&successfully_flattened)) return this;
+  return String::cast(successfully_flattened);
 }
 
 
@@ -2139,6 +2240,9 @@
       return ExternalAsciiString::cast(this)->ExternalAsciiStringGet(index);
     case kExternalStringTag | kTwoByteStringTag:
       return ExternalTwoByteString::cast(this)->ExternalTwoByteStringGet(index);
+    case kSlicedStringTag | kAsciiStringTag:
+    case kSlicedStringTag | kTwoByteStringTag:
+      return SlicedString::cast(this)->SlicedStringGet(index);
     default:
       break;
   }
@@ -2159,15 +2263,19 @@
 
 
 bool String::IsFlat() {
-  switch (StringShape(this).representation_tag()) {
-    case kConsStringTag: {
-      String* second = ConsString::cast(this)->second();
-      // Only flattened strings have second part empty.
-      return second->length() == 0;
-    }
-    default:
-      return true;
-  }
+  if (!StringShape(this).IsCons()) return true;
+  return ConsString::cast(this)->second()->length() == 0;
+}
+
+
+String* String::GetUnderlying() {
+  // Giving direct access to underlying string only makes sense if the
+  // wrapping string is already flattened.
+  ASSERT(this->IsFlat());
+  ASSERT(StringShape(this).IsIndirect());
+  STATIC_ASSERT(ConsString::kFirstOffset == SlicedString::kParentOffset);
+  const int kUnderlyingOffset = SlicedString::kParentOffset;
+  return String::cast(READ_FIELD(this, kUnderlyingOffset));
 }
 
 
@@ -2226,6 +2334,20 @@
 }
 
 
+String* SlicedString::parent() {
+  return String::cast(READ_FIELD(this, kParentOffset));
+}
+
+
+void SlicedString::set_parent(String* parent) {
+  ASSERT(parent->IsSeqString());
+  WRITE_FIELD(this, kParentOffset, parent);
+}
+
+
+SMI_ACCESSORS(SlicedString, offset, kOffsetOffset)
+
+
 String* ConsString::first() {
   return String::cast(READ_FIELD(this, kFirstOffset));
 }
@@ -2350,13 +2472,18 @@
 }
 
 
-uint8_t ExternalPixelArray::get(int index) {
+uint8_t ExternalPixelArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   uint8_t* ptr = external_pixel_pointer();
   return ptr[index];
 }
 
 
+MaybeObject* ExternalPixelArray::get(int index) {
+  return Smi::FromInt(static_cast<int>(get_scalar(index)));
+}
+
+
 void ExternalPixelArray::set(int index, uint8_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   uint8_t* ptr = external_pixel_pointer();
@@ -2376,13 +2503,18 @@
 }
 
 
-int8_t ExternalByteArray::get(int index) {
+int8_t ExternalByteArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   int8_t* ptr = static_cast<int8_t*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalByteArray::get(int index) {
+  return Smi::FromInt(static_cast<int>(get_scalar(index)));
+}
+
+
 void ExternalByteArray::set(int index, int8_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   int8_t* ptr = static_cast<int8_t*>(external_pointer());
@@ -2390,13 +2522,18 @@
 }
 
 
-uint8_t ExternalUnsignedByteArray::get(int index) {
+uint8_t ExternalUnsignedByteArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   uint8_t* ptr = static_cast<uint8_t*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalUnsignedByteArray::get(int index) {
+  return Smi::FromInt(static_cast<int>(get_scalar(index)));
+}
+
+
 void ExternalUnsignedByteArray::set(int index, uint8_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   uint8_t* ptr = static_cast<uint8_t*>(external_pointer());
@@ -2404,13 +2541,18 @@
 }
 
 
-int16_t ExternalShortArray::get(int index) {
+int16_t ExternalShortArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   int16_t* ptr = static_cast<int16_t*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalShortArray::get(int index) {
+  return Smi::FromInt(static_cast<int>(get_scalar(index)));
+}
+
+
 void ExternalShortArray::set(int index, int16_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   int16_t* ptr = static_cast<int16_t*>(external_pointer());
@@ -2418,13 +2560,18 @@
 }
 
 
-uint16_t ExternalUnsignedShortArray::get(int index) {
+uint16_t ExternalUnsignedShortArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   uint16_t* ptr = static_cast<uint16_t*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalUnsignedShortArray::get(int index) {
+  return Smi::FromInt(static_cast<int>(get_scalar(index)));
+}
+
+
 void ExternalUnsignedShortArray::set(int index, uint16_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   uint16_t* ptr = static_cast<uint16_t*>(external_pointer());
@@ -2432,13 +2579,18 @@
 }
 
 
-int32_t ExternalIntArray::get(int index) {
+int32_t ExternalIntArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   int32_t* ptr = static_cast<int32_t*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalIntArray::get(int index) {
+    return GetHeap()->NumberFromInt32(get_scalar(index));
+}
+
+
 void ExternalIntArray::set(int index, int32_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   int32_t* ptr = static_cast<int32_t*>(external_pointer());
@@ -2446,13 +2598,18 @@
 }
 
 
-uint32_t ExternalUnsignedIntArray::get(int index) {
+uint32_t ExternalUnsignedIntArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   uint32_t* ptr = static_cast<uint32_t*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalUnsignedIntArray::get(int index) {
+    return GetHeap()->NumberFromUint32(get_scalar(index));
+}
+
+
 void ExternalUnsignedIntArray::set(int index, uint32_t value) {
   ASSERT((index >= 0) && (index < this->length()));
   uint32_t* ptr = static_cast<uint32_t*>(external_pointer());
@@ -2460,13 +2617,18 @@
 }
 
 
-float ExternalFloatArray::get(int index) {
+float ExternalFloatArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   float* ptr = static_cast<float*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalFloatArray::get(int index) {
+    return GetHeap()->NumberFromDouble(get_scalar(index));
+}
+
+
 void ExternalFloatArray::set(int index, float value) {
   ASSERT((index >= 0) && (index < this->length()));
   float* ptr = static_cast<float*>(external_pointer());
@@ -2474,13 +2636,18 @@
 }
 
 
-double ExternalDoubleArray::get(int index) {
+double ExternalDoubleArray::get_scalar(int index) {
   ASSERT((index >= 0) && (index < this->length()));
   double* ptr = static_cast<double*>(external_pointer());
   return ptr[index];
 }
 
 
+MaybeObject* ExternalDoubleArray::get(int index) {
+    return GetHeap()->NumberFromDouble(get_scalar(index));
+}
+
+
 void ExternalDoubleArray::set(int index, double value) {
   ASSERT((index >= 0) && (index < this->length()));
   double* ptr = static_cast<double*>(external_pointer());
@@ -2757,7 +2924,8 @@
   ASSERT(kind() == STUB ||
          kind() == UNARY_OP_IC ||
          kind() == BINARY_OP_IC ||
-         kind() == COMPARE_IC);
+         kind() == COMPARE_IC ||
+         kind() == TO_BOOLEAN_IC);
   return READ_BYTE_FIELD(this, kStubMajorKeyOffset);
 }
 
@@ -2766,7 +2934,8 @@
   ASSERT(kind() == STUB ||
          kind() == UNARY_OP_IC ||
          kind() == BINARY_OP_IC ||
-         kind() == COMPARE_IC);
+         kind() == COMPARE_IC ||
+         kind() == TO_BOOLEAN_IC);
   ASSERT(0 <= major && major < 256);
   WRITE_BYTE_FIELD(this, kStubMajorKeyOffset, major);
 }
@@ -2908,6 +3077,17 @@
 }
 
 
+byte Code::to_boolean_state() {
+  ASSERT(is_to_boolean_ic_stub());
+  return READ_BYTE_FIELD(this, kToBooleanTypeOffset);
+}
+
+
+void Code::set_to_boolean_state(byte value) {
+  ASSERT(is_to_boolean_ic_stub());
+  WRITE_BYTE_FIELD(this, kToBooleanTypeOffset, value);
+}
+
 bool Code::is_inline_cache_stub() {
   Kind kind = this->kind();
   return kind >= FIRST_IC_KIND && kind <= LAST_IC_KIND;
@@ -3249,8 +3429,6 @@
 ACCESSORS(FunctionTemplateInfo, access_check_info, Object,
           kAccessCheckInfoOffset)
 ACCESSORS(FunctionTemplateInfo, flag, Smi, kFlagOffset)
-ACCESSORS(FunctionTemplateInfo, prototype_attributes, Smi,
-          kPrototypeAttributesOffset)
 
 ACCESSORS(ObjectTemplateInfo, constructor, Object, kConstructorOffset)
 ACCESSORS(ObjectTemplateInfo, internal_field_count, Object,
@@ -3305,6 +3483,8 @@
 BOOL_ACCESSORS(FunctionTemplateInfo, flag, undetectable, kUndetectableBit)
 BOOL_ACCESSORS(FunctionTemplateInfo, flag, needs_access_check,
                kNeedsAccessCheckBit)
+BOOL_ACCESSORS(FunctionTemplateInfo, flag, read_only_prototype,
+               kReadOnlyPrototypeBit)
 BOOL_ACCESSORS(SharedFunctionInfo, start_position_and_type, is_expression,
                kIsExpressionBit)
 BOOL_ACCESSORS(SharedFunctionInfo, start_position_and_type, is_toplevel,
@@ -3743,6 +3923,15 @@
 ACCESSORS(JSProxy, padding, Object, kPaddingOffset)
 
 
+ACCESSORS(JSWeakMap, table, ObjectHashTable, kTableOffset)
+ACCESSORS_GCSAFE(JSWeakMap, next, Object, kNextOffset)
+
+
+ObjectHashTable* JSWeakMap::unchecked_table() {
+  return reinterpret_cast<ObjectHashTable*>(READ_FIELD(this, kTableOffset));
+}
+
+
 Address Foreign::address() {
   return AddressFrom<Address>(READ_INTPTR_FIELD(this, kAddressOffset));
 }
@@ -3928,6 +4117,11 @@
 }
 
 
+ElementsAccessor* JSObject::GetElementsAccessor() {
+  return ElementsAccessor::ForKind(GetElementsKind());
+}
+
+
 bool JSObject::HasFastElements() {
   return GetElementsKind() == FAST_ELEMENTS;
 }
@@ -4201,6 +4395,11 @@
 }
 
 
+bool JSObject::HasHiddenProperties() {
+  return !GetHiddenProperties(OMIT_CREATION)->ToObjectChecked()->IsUndefined();
+}
+
+
 bool JSObject::HasElement(uint32_t index) {
   return HasElementWithReceiver(this, index);
 }
@@ -4316,6 +4515,36 @@
 }
 
 
+bool ObjectHashTableShape::IsMatch(JSObject* key, Object* other) {
+  return key == JSObject::cast(other);
+}
+
+
+uint32_t ObjectHashTableShape::Hash(JSObject* key) {
+  MaybeObject* maybe_hash = key->GetIdentityHash(JSObject::OMIT_CREATION);
+  ASSERT(!maybe_hash->IsFailure());
+  return Smi::cast(maybe_hash->ToObjectUnchecked())->value();
+}
+
+
+uint32_t ObjectHashTableShape::HashForObject(JSObject* key, Object* other) {
+  MaybeObject* maybe_hash = JSObject::cast(other)->GetIdentityHash(
+      JSObject::OMIT_CREATION);
+  ASSERT(!maybe_hash->IsFailure());
+  return Smi::cast(maybe_hash->ToObjectUnchecked())->value();
+}
+
+
+MaybeObject* ObjectHashTableShape::AsObject(JSObject* key) {
+  return key;
+}
+
+
+void ObjectHashTable::RemoveEntry(int entry) {
+  RemoveEntry(entry, GetHeap());
+}
+
+
 void Map::ClearCodeCache(Heap* heap) {
   // No write barrier is needed since empty_fixed_array is not in new space.
   // Please note this function is used during marking:
diff --git a/src/objects-printer.cc b/src/objects-printer.cc
index 158789e..3573572 100644
--- a/src/objects-printer.cc
+++ b/src/objects-printer.cc
@@ -1,4 +1,4 @@
-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -151,6 +151,9 @@
     case JS_PROXY_TYPE:
       JSProxy::cast(this)->JSProxyPrint(out);
       break;
+    case JS_WEAK_MAP_TYPE:
+      JSWeakMap::cast(this)->JSWeakMapPrint(out);
+      break;
     case FOREIGN_TYPE:
       Foreign::cast(this)->ForeignPrint(out);
       break;
@@ -282,17 +285,30 @@
       }
       break;
     }
+    case FAST_DOUBLE_ELEMENTS: {
+      // Print in array notation for non-sparse arrays.
+      FixedDoubleArray* p = FixedDoubleArray::cast(elements());
+      for (int i = 0; i < p->length(); i++) {
+        if (p->is_the_hole(i)) {
+          PrintF(out, "   %d: <the hole>", i);
+        } else {
+          PrintF(out, "   %d: %g", i, p->get_scalar(i));
+        }
+        PrintF(out, "\n");
+      }
+      break;
+    }
     case EXTERNAL_PIXEL_ELEMENTS: {
       ExternalPixelArray* p = ExternalPixelArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, p->get(i));
+        PrintF(out, "   %d: %d\n", i, p->get_scalar(i));
       }
       break;
     }
     case EXTERNAL_BYTE_ELEMENTS: {
       ExternalByteArray* p = ExternalByteArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get(i)));
+        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get_scalar(i)));
       }
       break;
     }
@@ -300,14 +316,14 @@
       ExternalUnsignedByteArray* p =
           ExternalUnsignedByteArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get(i)));
+        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get_scalar(i)));
       }
       break;
     }
     case EXTERNAL_SHORT_ELEMENTS: {
       ExternalShortArray* p = ExternalShortArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get(i)));
+        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get_scalar(i)));
       }
       break;
     }
@@ -315,14 +331,14 @@
       ExternalUnsignedShortArray* p =
           ExternalUnsignedShortArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get(i)));
+        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get_scalar(i)));
       }
       break;
     }
     case EXTERNAL_INT_ELEMENTS: {
       ExternalIntArray* p = ExternalIntArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get(i)));
+        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get_scalar(i)));
       }
       break;
     }
@@ -330,21 +346,21 @@
       ExternalUnsignedIntArray* p =
           ExternalUnsignedIntArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get(i)));
+        PrintF(out, "   %d: %d\n", i, static_cast<int>(p->get_scalar(i)));
       }
       break;
     }
     case EXTERNAL_FLOAT_ELEMENTS: {
       ExternalFloatArray* p = ExternalFloatArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "   %d: %f\n", i, p->get(i));
+        PrintF(out, "   %d: %f\n", i, p->get_scalar(i));
       }
       break;
     }
     case EXTERNAL_DOUBLE_ELEMENTS: {
       ExternalDoubleArray* p = ExternalDoubleArray::cast(elements());
       for (int i = 0; i < p->length(); i++) {
-        PrintF(out, "  %d: %f\n", i, p->get(i));
+        PrintF(out, "  %d: %f\n", i, p->get_scalar(i));
       }
       break;
     }
@@ -360,9 +376,6 @@
       }
       break;
     }
-    default:
-      UNREACHABLE();
-      break;
   }
 }
 
@@ -421,6 +434,7 @@
     case CODE_TYPE: return "CODE";
     case JS_ARRAY_TYPE: return "JS_ARRAY";
     case JS_PROXY_TYPE: return "JS_PROXY";
+    case JS_WEAK_MAP_TYPE: return "JS_WEAK_MAP";
     case JS_REGEXP_TYPE: return "JS_REGEXP";
     case JS_VALUE_TYPE: return "JS_VALUE";
     case JS_GLOBAL_OBJECT_TYPE: return "JS_GLOBAL_OBJECT";
@@ -550,6 +564,21 @@
 }
 
 
+// This method is only meant to be called from gdb for debugging purposes.
+// Since the string can also be in two-byte encoding, non-ascii characters
+// will be ignored in the output.
+char* String::ToAsciiArray() {
+  // Static so that subsequent calls frees previously allocated space.
+  // This also means that previous results will be overwritten.
+  static char* buffer = NULL;
+  if (buffer != NULL) free(buffer);
+  buffer = new char[length()+1];
+  WriteToFlat(this, buffer, 0, length());
+  buffer[length()] = 0;
+  return buffer;
+}
+
+
 void JSProxy::JSProxyPrint(FILE* out) {
   HeapObject::PrintHeader(out, "JSProxy");
   PrintF(out, " - map = 0x%p\n", reinterpret_cast<void*>(map()));
@@ -559,6 +588,16 @@
 }
 
 
+void JSWeakMap::JSWeakMapPrint(FILE* out) {
+  HeapObject::PrintHeader(out, "JSWeakMap");
+  PrintF(out, " - map = 0x%p\n", reinterpret_cast<void*>(map()));
+  PrintF(out, " - number of elements = %d\n", table()->NumberOfElements());
+  PrintF(out, " - table = ");
+  table()->ShortPrint(out);
+  PrintF(out, "\n");
+}
+
+
 void JSFunction::JSFunctionPrint(FILE* out) {
   HeapObject::PrintHeader(out, "Function");
   PrintF(out, " - map = 0x%p\n", reinterpret_cast<void*>(map()));
diff --git a/src/objects-visiting.cc b/src/objects-visiting.cc
index 4cd795e..bde9e83 100644
--- a/src/objects-visiting.cc
+++ b/src/objects-visiting.cc
@@ -58,6 +58,9 @@
           return kVisitConsString;
         }
 
+      case kSlicedStringTag:
+        return kVisitSlicedString;
+
       case kExternalStringTag:
         return GetVisitorIdForSize(kVisitDataObject,
                                    kVisitDataObjectGeneric,
@@ -88,6 +91,9 @@
     case JS_GLOBAL_PROPERTY_CELL_TYPE:
       return kVisitPropertyCell;
 
+    case JS_WEAK_MAP_TYPE:
+      return kVisitJSWeakMap;
+
     case JS_REGEXP_TYPE:
       return kVisitJSRegExp;
 
diff --git a/src/objects-visiting.h b/src/objects-visiting.h
index cc64763..4ce1bd0 100644
--- a/src/objects-visiting.h
+++ b/src/objects-visiting.h
@@ -115,12 +115,14 @@
     kVisitStructGeneric,
 
     kVisitConsString,
+    kVisitSlicedString,
     kVisitOddball,
     kVisitCode,
     kVisitMap,
     kVisitPropertyCell,
     kVisitSharedFunctionInfo,
     kVisitJSFunction,
+    kVisitJSWeakMap,
     kVisitJSRegExp,
 
     kVisitorIdCount,
@@ -298,6 +300,11 @@
                                       ConsString::BodyDescriptor,
                                       int>::Visit);
 
+    table_.Register(kVisitSlicedString,
+                    &FixedBodyVisitor<StaticVisitor,
+                                      SlicedString::BodyDescriptor,
+                                      int>::Visit);
+
     table_.Register(kVisitFixedArray,
                     &FlexibleBodyVisitor<StaticVisitor,
                                          FixedArray::BodyDescriptor,
@@ -317,7 +324,9 @@
                                       SharedFunctionInfo::BodyDescriptor,
                                       int>::Visit);
 
-    table_.Register(kVisitJSRegExp, &VisitJSRegExp);
+    table_.Register(kVisitJSWeakMap, &VisitJSObject);
+
+    table_.Register(kVisitJSRegExp, &VisitJSObject);
 
     table_.Register(kVisitSeqAsciiString, &VisitSeqAsciiString);
 
@@ -356,15 +365,15 @@
     return FixedDoubleArray::SizeFor(length);
   }
 
+  static inline int VisitJSObject(Map* map, HeapObject* object) {
+    return JSObjectVisitor::Visit(map, object);
+  }
+
   static inline int VisitSeqAsciiString(Map* map, HeapObject* object) {
     return SeqAsciiString::cast(object)->
         SeqAsciiStringSize(map->instance_type());
   }
 
-  static inline int VisitJSRegExp(Map* map, HeapObject* object) {
-    return JSObjectVisitor::Visit(map, object);
-  }
-
   static inline int VisitSeqTwoByteString(Map* map, HeapObject* object) {
     return SeqTwoByteString::cast(object)->
         SeqTwoByteStringSize(map->instance_type());
diff --git a/src/objects.cc b/src/objects.cc
index 1ab5dd2..0660dba 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -33,6 +33,7 @@
 #include "codegen.h"
 #include "debug.h"
 #include "deoptimizer.h"
+#include "elements.h"
 #include "execution.h"
 #include "full-codegen.h"
 #include "hydrogen.h"
@@ -602,36 +603,69 @@
 
 
 MaybeObject* Object::GetElementWithReceiver(Object* receiver, uint32_t index) {
-  Object* holder = NULL;
-  if (IsSmi()) {
-    Context* global_context = Isolate::Current()->context()->global_context();
-    holder = global_context->number_function()->instance_prototype();
-  } else {
-    HeapObject* heap_object = HeapObject::cast(this);
+  Heap* heap = IsSmi()
+      ? Isolate::Current()->heap()
+      : HeapObject::cast(this)->GetHeap();
+  Object* holder = this;
 
-    if (heap_object->IsJSObject()) {
-      return JSObject::cast(this)->GetElementWithReceiver(receiver, index);
-    }
-    Heap* heap = heap_object->GetHeap();
-    Isolate* isolate = heap->isolate();
-
-    Context* global_context = isolate->context()->global_context();
-    if (heap_object->IsString()) {
-      holder = global_context->string_function()->instance_prototype();
-    } else if (heap_object->IsHeapNumber()) {
+  // Iterate up the prototype chain until an element is found or the null
+  // prototype is encountered.
+  for (holder = this;
+       holder != heap->null_value();
+       holder = holder->GetPrototype()) {
+    if (holder->IsSmi()) {
+      Context* global_context = Isolate::Current()->context()->global_context();
       holder = global_context->number_function()->instance_prototype();
-    } else if (heap_object->IsBoolean()) {
-      holder = global_context->boolean_function()->instance_prototype();
-    } else if (heap_object->IsJSProxy()) {
-      return heap->undefined_value();  // For now...
     } else {
-      // Undefined and null have no indexed properties.
-      ASSERT(heap_object->IsUndefined() || heap_object->IsNull());
-      return heap->undefined_value();
+      HeapObject* heap_object = HeapObject::cast(holder);
+      if (!heap_object->IsJSObject()) {
+        Isolate* isolate = heap->isolate();
+        Context* global_context = isolate->context()->global_context();
+        if (heap_object->IsString()) {
+          holder = global_context->string_function()->instance_prototype();
+        } else if (heap_object->IsHeapNumber()) {
+          holder = global_context->number_function()->instance_prototype();
+        } else if (heap_object->IsBoolean()) {
+          holder = global_context->boolean_function()->instance_prototype();
+        } else if (heap_object->IsJSProxy()) {
+          return heap->undefined_value();  // For now...
+        } else {
+          // Undefined and null have no indexed properties.
+          ASSERT(heap_object->IsUndefined() || heap_object->IsNull());
+          return heap->undefined_value();
+        }
+      }
+    }
+
+    // Inline the case for JSObjects. Doing so significantly improves the
+    // performance of fetching elements where checking the prototype chain is
+    // necessary.
+    JSObject* js_object = JSObject::cast(holder);
+
+    // Check access rights if needed.
+    if (js_object->IsAccessCheckNeeded()) {
+      Isolate* isolate = heap->isolate();
+      if (!isolate->MayIndexedAccess(js_object, index, v8::ACCESS_GET)) {
+        isolate->ReportFailedAccessCheck(js_object, v8::ACCESS_GET);
+        return heap->undefined_value();
+      }
+    }
+
+    if (js_object->HasIndexedInterceptor()) {
+      return js_object->GetElementWithInterceptor(receiver, index);
+    }
+
+    if (js_object->elements() != heap->empty_fixed_array()) {
+      MaybeObject* result = js_object->GetElementsAccessor()->Get(
+          js_object->elements(),
+          index,
+          js_object,
+          receiver);
+      if (result != heap->the_hole_value()) return result;
     }
   }
 
-  return JSObject::cast(holder)->GetElementWithReceiver(receiver, index);
+  return heap->undefined_value();
 }
 
 
@@ -962,6 +996,11 @@
       accumulator->Add("<JS array[%u]>", static_cast<uint32_t>(length));
       break;
     }
+    case JS_WEAK_MAP_TYPE: {
+      int elements = JSWeakMap::cast(this)->table()->NumberOfElements();
+      accumulator->Add("<JS WeakMap[%d]>", elements);
+      break;
+    }
     case JS_REGEXP_TYPE: {
       accumulator->Add("<JS RegExp>");
       break;
@@ -1168,6 +1207,9 @@
       case kConsStringTag:
         ConsString::BodyDescriptor::IterateBody(this, v);
         break;
+      case kSlicedStringTag:
+        SlicedString::BodyDescriptor::IterateBody(this, v);
+        break;
       case kExternalStringTag:
         if ((type & kStringEncodingMask) == kAsciiStringTag) {
           reinterpret_cast<ExternalAsciiString*>(this)->
@@ -1191,6 +1233,7 @@
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
     case JS_VALUE_TYPE:
     case JS_ARRAY_TYPE:
+    case JS_WEAK_MAP_TYPE:
     case JS_REGEXP_TYPE:
     case JS_GLOBAL_PROXY_TYPE:
     case JS_GLOBAL_OBJECT_TYPE:
@@ -2278,7 +2321,8 @@
   if (has_exception) return Failure::Exception();
 
   Object* bool_result = result->ToBoolean();
-  if (mode == STRICT_DELETION && bool_result == GetHeap()->false_value()) {
+  if (mode == STRICT_DELETION &&
+      bool_result == isolate->heap()->false_value()) {
     Handle<Object> args[] = { handler, trap_name };
     Handle<Object> error = isolate->factory()->NewTypeError(
         "handler_failed", HandleVector(args, ARRAY_SIZE(args)));
@@ -2330,7 +2374,7 @@
   Handle<JSProxy> self(this);
 
   isolate->factory()->BecomeJSObject(self);
-  ASSERT(IsJSObject());
+  ASSERT(self->IsJSObject());
   // TODO(rossberg): recognize function proxies.
 }
 
@@ -2470,6 +2514,9 @@
 // callback setter removed.  The two lines looking up the LookupResult
 // result are also added.  If one of the functions is changed, the other
 // should be.
+// Note that this method cannot be used to set the prototype of a function
+// because ConvertDescriptorToField() which is called in "case CALLBACKS:"
+// doesn't handle function prototypes correctly.
 MaybeObject* JSObject::SetLocalPropertyIgnoreAttributes(
     String* name,
     Object* value,
@@ -2895,9 +2942,12 @@
   int length = IsJSArray()
       ? Smi::cast(JSArray::cast(this)->length())->value()
       : array->length();
+  int old_capacity = 0;
+  int used_elements = 0;
+  GetElementsCapacityAndUsage(&old_capacity, &used_elements);
   NumberDictionary* dictionary = NULL;
   { Object* object;
-    MaybeObject* maybe = NumberDictionary::Allocate(length);
+    MaybeObject* maybe = NumberDictionary::Allocate(used_elements);
     if (!maybe->ToObject(&object)) return maybe;
     dictionary = NumberDictionary::cast(object);
   }
@@ -2916,7 +2966,7 @@
         // exceed the capacity of new space, and we would fail repeatedly
         // trying to convert the FixedDoubleArray.
         MaybeObject* maybe_value_object =
-            GetHeap()->AllocateHeapNumber(double_array->get(i), TENURED);
+            GetHeap()->AllocateHeapNumber(double_array->get_scalar(i), TENURED);
         if (!maybe_value_object->ToObject(&value)) return maybe_value_object;
       }
     } else {
@@ -2960,6 +3010,98 @@
 }
 
 
+MaybeObject* JSObject::GetHiddenProperties(HiddenPropertiesFlag flag) {
+  Isolate* isolate = GetIsolate();
+  Heap* heap = isolate->heap();
+  Object* holder = BypassGlobalProxy();
+  if (holder->IsUndefined()) return heap->undefined_value();
+  JSObject* obj = JSObject::cast(holder);
+  if (obj->HasFastProperties()) {
+    // If the object has fast properties, check whether the first slot
+    // in the descriptor array matches the hidden symbol. Since the
+    // hidden symbols hash code is zero (and no other string has hash
+    // code zero) it will always occupy the first entry if present.
+    DescriptorArray* descriptors = obj->map()->instance_descriptors();
+    if ((descriptors->number_of_descriptors() > 0) &&
+        (descriptors->GetKey(0) == heap->hidden_symbol()) &&
+        descriptors->IsProperty(0)) {
+      ASSERT(descriptors->GetType(0) == FIELD);
+      return obj->FastPropertyAt(descriptors->GetFieldIndex(0));
+    }
+  }
+
+  // Only attempt to find the hidden properties in the local object and not
+  // in the prototype chain.
+  if (!obj->HasHiddenPropertiesObject()) {
+    // Hidden properties object not found. Allocate a new hidden properties
+    // object if requested. Otherwise return the undefined value.
+    if (flag == ALLOW_CREATION) {
+      Object* hidden_obj;
+      { MaybeObject* maybe_obj = heap->AllocateJSObject(
+            isolate->context()->global_context()->object_function());
+        if (!maybe_obj->ToObject(&hidden_obj)) return maybe_obj;
+      }
+      // Don't allow leakage of the hidden object through accessors
+      // on Object.prototype.
+      {
+        MaybeObject* maybe_obj =
+            JSObject::cast(hidden_obj)->SetPrototype(heap->null_value(), false);
+        if (maybe_obj->IsFailure()) return maybe_obj;
+      }
+      return obj->SetHiddenPropertiesObject(hidden_obj);
+    } else {
+      return heap->undefined_value();
+    }
+  }
+  return obj->GetHiddenPropertiesObject();
+}
+
+
+MaybeObject* JSObject::GetIdentityHash(HiddenPropertiesFlag flag) {
+  Isolate* isolate = GetIsolate();
+  Object* hidden_props_obj;
+  { MaybeObject* maybe_obj = GetHiddenProperties(flag);
+    if (!maybe_obj->ToObject(&hidden_props_obj)) return maybe_obj;
+  }
+  if (!hidden_props_obj->IsJSObject()) {
+    // We failed to create hidden properties.  That's a detached
+    // global proxy.
+    ASSERT(hidden_props_obj->IsUndefined());
+    return Smi::FromInt(0);
+  }
+  JSObject* hidden_props = JSObject::cast(hidden_props_obj);
+  String* hash_symbol = isolate->heap()->identity_hash_symbol();
+  {
+    // Note that HasLocalProperty() can cause a GC in the general case in the
+    // presence of interceptors.
+    AssertNoAllocation no_alloc;
+    if (hidden_props->HasLocalProperty(hash_symbol)) {
+      MaybeObject* hash = hidden_props->GetProperty(hash_symbol);
+      return Smi::cast(hash->ToObjectChecked());
+    }
+  }
+
+  int hash_value;
+  int attempts = 0;
+  do {
+    // Generate a random 32-bit hash value but limit range to fit
+    // within a smi.
+    hash_value = V8::Random(isolate) & Smi::kMaxValue;
+    attempts++;
+  } while (hash_value == 0 && attempts < 30);
+  hash_value = hash_value != 0 ? hash_value : 1;  // never return 0
+
+  Smi* hash = Smi::FromInt(hash_value);
+  { MaybeObject* result = hidden_props->SetLocalPropertyIgnoreAttributes(
+        hash_symbol,
+        hash,
+        static_cast<PropertyAttributes>(None));
+    if (result->IsFailure()) return result;
+  }
+  return hash;
+}
+
+
 MaybeObject* JSObject::DeletePropertyPostInterceptor(String* name,
                                                      DeleteMode mode) {
   // Check local property, ignore interceptor.
@@ -3009,48 +3151,6 @@
 }
 
 
-MaybeObject* JSObject::DeleteElementPostInterceptor(uint32_t index,
-                                                    DeleteMode mode) {
-  ASSERT(!HasExternalArrayElements());
-  switch (GetElementsKind()) {
-    case FAST_ELEMENTS: {
-      Object* obj;
-      { MaybeObject* maybe_obj = EnsureWritableFastElements();
-        if (!maybe_obj->ToObject(&obj)) return maybe_obj;
-      }
-      uint32_t length = IsJSArray() ?
-      static_cast<uint32_t>(Smi::cast(JSArray::cast(this)->length())->value()) :
-      static_cast<uint32_t>(FixedArray::cast(elements())->length());
-      if (index < length) {
-        FixedArray::cast(elements())->set_the_hole(index);
-      }
-      break;
-    }
-    case DICTIONARY_ELEMENTS: {
-      NumberDictionary* dictionary = element_dictionary();
-      int entry = dictionary->FindEntry(index);
-      if (entry != NumberDictionary::kNotFound) {
-        Object* deleted = dictionary->DeleteProperty(entry, mode);
-        if (deleted == GetHeap()->true_value()) {
-          MaybeObject* maybe_elements = dictionary->Shrink(index);
-          FixedArray* new_elements = NULL;
-          if (!maybe_elements->To(&new_elements)) {
-            return maybe_elements;
-          }
-          set_elements(new_elements);
-        }
-        return deleted;
-      }
-      break;
-    }
-    default:
-      UNREACHABLE();
-      break;
-  }
-  return GetHeap()->true_value();
-}
-
-
 MaybeObject* JSObject::DeleteElementWithInterceptor(uint32_t index) {
   Isolate* isolate = GetIsolate();
   Heap* heap = isolate->heap();
@@ -3078,100 +3178,15 @@
     ASSERT(result->IsBoolean());
     return *v8::Utils::OpenHandle(*result);
   }
-  MaybeObject* raw_result =
-      this_handle->DeleteElementPostInterceptor(index, NORMAL_DELETION);
+  MaybeObject* raw_result = this_handle->GetElementsAccessor()->Delete(
+      *this_handle,
+      index,
+      NORMAL_DELETION);
   RETURN_IF_SCHEDULED_EXCEPTION(isolate);
   return raw_result;
 }
 
 
-MaybeObject* JSObject::DeleteFastElement(uint32_t index) {
-  ASSERT(HasFastElements() || HasFastArgumentsElements());
-  Heap* heap = GetHeap();
-  FixedArray* backing_store = FixedArray::cast(elements());
-  if (backing_store->map() == heap->non_strict_arguments_elements_map()) {
-    backing_store = FixedArray::cast(backing_store->get(1));
-  } else {
-    Object* writable;
-    MaybeObject* maybe = EnsureWritableFastElements();
-    if (!maybe->ToObject(&writable)) return maybe;
-    backing_store = FixedArray::cast(writable);
-  }
-  uint32_t length = static_cast<uint32_t>(
-      IsJSArray()
-      ? Smi::cast(JSArray::cast(this)->length())->value()
-      : backing_store->length());
-  if (index < length) {
-    backing_store->set_the_hole(index);
-    // If an old space backing store is larger than a certain size and
-    // has too few used values, normalize it.
-    // To avoid doing the check on every delete we require at least
-    // one adjacent hole to the value being deleted.
-    Object* hole = heap->the_hole_value();
-    const int kMinLengthForSparsenessCheck = 64;
-    if (backing_store->length() >= kMinLengthForSparsenessCheck &&
-        !heap->InNewSpace(backing_store) &&
-        ((index > 0 && backing_store->get(index - 1) == hole) ||
-         (index + 1 < length && backing_store->get(index + 1) == hole))) {
-      int num_used = 0;
-      for (int i = 0; i < backing_store->length(); ++i) {
-        if (backing_store->get(i) != hole) ++num_used;
-        // Bail out early if more than 1/4 is used.
-        if (4 * num_used > backing_store->length()) break;
-      }
-      if (4 * num_used <= backing_store->length()) {
-        MaybeObject* result = NormalizeElements();
-        if (result->IsFailure()) return result;
-      }
-    }
-  }
-  return heap->true_value();
-}
-
-
-MaybeObject* JSObject::DeleteDictionaryElement(uint32_t index,
-                                               DeleteMode mode) {
-  Isolate* isolate = GetIsolate();
-  Heap* heap = isolate->heap();
-  FixedArray* backing_store = FixedArray::cast(elements());
-  bool is_arguments =
-      (GetElementsKind() == JSObject::NON_STRICT_ARGUMENTS_ELEMENTS);
-  if (is_arguments) {
-    backing_store = FixedArray::cast(backing_store->get(1));
-  }
-  NumberDictionary* dictionary = NumberDictionary::cast(backing_store);
-  int entry = dictionary->FindEntry(index);
-  if (entry != NumberDictionary::kNotFound) {
-    Object* result = dictionary->DeleteProperty(entry, mode);
-    if (result == heap->true_value()) {
-      MaybeObject* maybe_elements = dictionary->Shrink(index);
-      FixedArray* new_elements = NULL;
-      if (!maybe_elements->To(&new_elements)) {
-        return maybe_elements;
-      }
-      if (is_arguments) {
-        FixedArray::cast(elements())->set(1, new_elements);
-      } else {
-        set_elements(new_elements);
-      }
-    }
-    if (mode == STRICT_DELETION && result == heap->false_value()) {
-      // In strict mode, attempting to delete a non-configurable property
-      // throws an exception.
-      HandleScope scope(isolate);
-      Handle<Object> holder(this);
-      Handle<Object> name = isolate->factory()->NewNumberFromUint(index);
-      Handle<Object> args[2] = { name, holder };
-      Handle<Object> error =
-          isolate->factory()->NewTypeError("strict_delete_property",
-                                           HandleVector(args, 2));
-      return isolate->Throw(*error);
-    }
-  }
-  return heap->true_value();
-}
-
-
 MaybeObject* JSObject::DeleteElement(uint32_t index, DeleteMode mode) {
   Isolate* isolate = GetIsolate();
   // Check access rights if needed.
@@ -3190,62 +3205,13 @@
 
   if (HasIndexedInterceptor()) {
     // Skip interceptor if forcing deletion.
-    return (mode == FORCE_DELETION)
-        ? DeleteElementPostInterceptor(index, FORCE_DELETION)
-        : DeleteElementWithInterceptor(index);
+    if (mode != FORCE_DELETION) {
+      return DeleteElementWithInterceptor(index);
+    }
+    mode = JSReceiver::FORCE_DELETION;
   }
 
-  switch (GetElementsKind()) {
-    case FAST_ELEMENTS:
-      return DeleteFastElement(index);
-
-    case DICTIONARY_ELEMENTS:
-      return DeleteDictionaryElement(index, mode);
-
-    case FAST_DOUBLE_ELEMENTS: {
-      int length = IsJSArray()
-          ? Smi::cast(JSArray::cast(this)->length())->value()
-          : FixedDoubleArray::cast(elements())->length();
-      if (index < static_cast<uint32_t>(length)) {
-        FixedDoubleArray::cast(elements())->set_the_hole(index);
-      }
-      break;
-    }
-    case EXTERNAL_PIXEL_ELEMENTS:
-    case EXTERNAL_BYTE_ELEMENTS:
-    case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-    case EXTERNAL_SHORT_ELEMENTS:
-    case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-    case EXTERNAL_INT_ELEMENTS:
-    case EXTERNAL_UNSIGNED_INT_ELEMENTS:
-    case EXTERNAL_FLOAT_ELEMENTS:
-    case EXTERNAL_DOUBLE_ELEMENTS:
-      // Pixel and external array elements cannot be deleted. Just
-      // silently ignore here.
-      break;
-
-    case NON_STRICT_ARGUMENTS_ELEMENTS: {
-      FixedArray* parameter_map = FixedArray::cast(elements());
-      uint32_t length = parameter_map->length();
-      Object* probe =
-          index < (length - 2) ? parameter_map->get(index + 2) : NULL;
-      if (probe != NULL && !probe->IsTheHole()) {
-        // TODO(kmillikin): We could check if this was the last aliased
-        // parameter, and revert to normal elements in that case.  That
-        // would enable GC of the context.
-        parameter_map->set_the_hole(index + 2);
-      } else {
-        FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
-        if (arguments->IsDictionary()) {
-          return DeleteDictionaryElement(index, mode);
-        } else {
-          return DeleteFastElement(index);
-        }
-      }
-      break;
-    }
-  }
-  return isolate->heap()->true_value();
+  return GetElementsAccessor()->Delete(this, index, mode);
 }
 
 
@@ -3666,6 +3632,7 @@
   if (is_element) {
     switch (GetElementsKind()) {
       case FAST_ELEMENTS:
+      case FAST_DOUBLE_ELEMENTS:
         break;
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_BYTE_ELEMENTS:
@@ -3676,7 +3643,6 @@
       case EXTERNAL_UNSIGNED_INT_ELEMENTS:
       case EXTERNAL_FLOAT_ELEMENTS:
       case EXTERNAL_DOUBLE_ELEMENTS:
-      case FAST_DOUBLE_ELEMENTS:
         // Ignore getters and setters on pixel and external array
         // elements.
         return heap->undefined_value();
@@ -3915,6 +3881,7 @@
     // Accessors overwrite previous callbacks (cf. with getters/setters).
     switch (GetElementsKind()) {
       case FAST_ELEMENTS:
+      case FAST_DOUBLE_ELEMENTS:
         break;
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_BYTE_ELEMENTS:
@@ -3925,7 +3892,6 @@
       case EXTERNAL_UNSIGNED_INT_ELEMENTS:
       case EXTERNAL_FLOAT_ELEMENTS:
       case EXTERNAL_DOUBLE_ELEMENTS:
-      case FAST_DOUBLE_ELEMENTS:
         // Ignore getters and setters on pixel and external array
         // elements.
         return isolate->heap()->undefined_value();
@@ -4521,20 +4487,6 @@
 }
 
 
-static bool HasKey(FixedArray* array, Object* key) {
-  int len0 = array->length();
-  for (int i = 0; i < len0; i++) {
-    Object* element = array->get(i);
-    if (element->IsSmi() && key->IsSmi() && (element == key)) return true;
-    if (element->IsString() &&
-        key->IsString() && String::cast(element)->Equals(String::cast(key))) {
-      return true;
-    }
-  }
-  return false;
-}
-
-
 MaybeObject* PolymorphicCodeCache::Update(MapList* maps,
                                           Code::Flags flags,
                                           Code* code) {
@@ -4694,102 +4646,37 @@
 
 
 MaybeObject* FixedArray::AddKeysFromJSArray(JSArray* array) {
-  ASSERT(!array->HasExternalArrayElements());
-  switch (array->GetElementsKind()) {
-    case JSObject::FAST_ELEMENTS:
-      return UnionOfKeys(FixedArray::cast(array->elements()));
-    case JSObject::DICTIONARY_ELEMENTS: {
-      NumberDictionary* dict = array->element_dictionary();
-      int size = dict->NumberOfElements();
-
-      // Allocate a temporary fixed array.
-      Object* object;
-      { MaybeObject* maybe_object = GetHeap()->AllocateFixedArray(size);
-        if (!maybe_object->ToObject(&object)) return maybe_object;
-      }
-      FixedArray* key_array = FixedArray::cast(object);
-
-      int capacity = dict->Capacity();
-      int pos = 0;
-      // Copy the elements from the JSArray to the temporary fixed array.
-      for (int i = 0; i < capacity; i++) {
-        if (dict->IsKey(dict->KeyAt(i))) {
-          key_array->set(pos++, dict->ValueAt(i));
-        }
-      }
-      // Compute the union of this and the temporary fixed array.
-      return UnionOfKeys(key_array);
+  ElementsAccessor* accessor = array->GetElementsAccessor();
+  MaybeObject* maybe_result =
+      accessor->AddElementsToFixedArray(array->elements(), this, array, array);
+  FixedArray* result;
+  if (!maybe_result->To<FixedArray>(&result)) return maybe_result;
+#ifdef DEBUG
+  if (FLAG_enable_slow_asserts) {
+    for (int i = 0; i < result->length(); i++) {
+      Object* current = result->get(i);
+      ASSERT(current->IsNumber() || current->IsString());
     }
-    case JSObject::NON_STRICT_ARGUMENTS_ELEMENTS:
-      UNIMPLEMENTED();
-      break;
-    case JSObject::EXTERNAL_BYTE_ELEMENTS:
-    case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-    case JSObject::EXTERNAL_SHORT_ELEMENTS:
-    case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-    case JSObject::EXTERNAL_INT_ELEMENTS:
-    case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
-    case JSObject::EXTERNAL_FLOAT_ELEMENTS:
-    case JSObject::EXTERNAL_DOUBLE_ELEMENTS:
-    case JSObject::EXTERNAL_PIXEL_ELEMENTS:
-    case JSObject::FAST_DOUBLE_ELEMENTS:
-      break;
   }
-  UNREACHABLE();
-  return GetHeap()->null_value();  // Failure case needs to "return" a value.
+#endif
+  return result;
 }
 
 
 MaybeObject* FixedArray::UnionOfKeys(FixedArray* other) {
-  int len0 = length();
+  ElementsAccessor* accessor = ElementsAccessor::ForArray(other);
+  MaybeObject* maybe_result =
+      accessor->AddElementsToFixedArray(other, this, NULL, NULL);
+  FixedArray* result;
+  if (!maybe_result->To<FixedArray>(&result)) return maybe_result;
 #ifdef DEBUG
   if (FLAG_enable_slow_asserts) {
-    for (int i = 0; i < len0; i++) {
-      ASSERT(get(i)->IsString() || get(i)->IsNumber());
+    for (int i = 0; i < result->length(); i++) {
+      Object* current = result->get(i);
+      ASSERT(current->IsNumber() || current->IsString());
     }
   }
 #endif
-  int len1 = other->length();
-  // Optimize if 'other' is empty.
-  // We cannot optimize if 'this' is empty, as other may have holes
-  // or non keys.
-  if (len1 == 0) return this;
-
-  // Compute how many elements are not in this.
-  int extra = 0;
-  for (int y = 0; y < len1; y++) {
-    Object* value = other->get(y);
-    if (!value->IsTheHole() && !HasKey(this, value)) extra++;
-  }
-
-  if (extra == 0) return this;
-
-  // Allocate the result
-  Object* obj;
-  { MaybeObject* maybe_obj = GetHeap()->AllocateFixedArray(len0 + extra);
-    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
-  }
-  // Fill in the content
-  AssertNoAllocation no_gc;
-  FixedArray* result = FixedArray::cast(obj);
-  WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
-  for (int i = 0; i < len0; i++) {
-    Object* e = get(i);
-    ASSERT(e->IsString() || e->IsNumber());
-    result->set(i, e, mode);
-  }
-  // Fill in the extra keys.
-  int index = 0;
-  for (int y = 0; y < len1; y++) {
-    Object* value = other->get(y);
-    if (!value->IsTheHole() && !HasKey(this, value)) {
-      Object* e = other->get(y);
-      ASSERT(e->IsString() || e->IsNumber());
-      result->set(len0 + index, e, mode);
-      index++;
-    }
-  }
-  ASSERT(extra == index);
   return result;
 }
 
@@ -5171,55 +5058,45 @@
 }
 
 
-Vector<const char> String::ToAsciiVector() {
-  ASSERT(IsAsciiRepresentation());
-  ASSERT(IsFlat());
-
-  int offset = 0;
+String::FlatContent String::GetFlatContent() {
   int length = this->length();
-  StringRepresentationTag string_tag = StringShape(this).representation_tag();
+  StringShape shape(this);
   String* string = this;
-  if (string_tag == kConsStringTag) {
-    ConsString* cons = ConsString::cast(string);
-    ASSERT(cons->second()->length() == 0);
-    string = cons->first();
-    string_tag = StringShape(string).representation_tag();
-  }
-  if (string_tag == kSeqStringTag) {
-    SeqAsciiString* seq = SeqAsciiString::cast(string);
-    char* start = seq->GetChars();
-    return Vector<const char>(start + offset, length);
-  }
-  ASSERT(string_tag == kExternalStringTag);
-  ExternalAsciiString* ext = ExternalAsciiString::cast(string);
-  const char* start = ext->resource()->data();
-  return Vector<const char>(start + offset, length);
-}
-
-
-Vector<const uc16> String::ToUC16Vector() {
-  ASSERT(IsTwoByteRepresentation());
-  ASSERT(IsFlat());
-
   int offset = 0;
-  int length = this->length();
-  StringRepresentationTag string_tag = StringShape(this).representation_tag();
-  String* string = this;
-  if (string_tag == kConsStringTag) {
+  if (shape.representation_tag() == kConsStringTag) {
     ConsString* cons = ConsString::cast(string);
-    ASSERT(cons->second()->length() == 0);
+    if (cons->second()->length() != 0) {
+      return FlatContent();
+    }
     string = cons->first();
-    string_tag = StringShape(string).representation_tag();
+    shape = StringShape(string);
   }
-  if (string_tag == kSeqStringTag) {
-    SeqTwoByteString* seq = SeqTwoByteString::cast(string);
-    return Vector<const uc16>(seq->GetChars() + offset, length);
+  if (shape.representation_tag() == kSlicedStringTag) {
+    SlicedString* slice = SlicedString::cast(string);
+    offset = slice->offset();
+    string = slice->parent();
+    shape = StringShape(string);
+    ASSERT(shape.representation_tag() != kConsStringTag &&
+           shape.representation_tag() != kSlicedStringTag);
   }
-  ASSERT(string_tag == kExternalStringTag);
-  ExternalTwoByteString* ext = ExternalTwoByteString::cast(string);
-  const uc16* start =
-      reinterpret_cast<const uc16*>(ext->resource()->data());
-  return Vector<const uc16>(start + offset, length);
+  if (shape.encoding_tag() == kAsciiStringTag) {
+    const char* start;
+    if (shape.representation_tag() == kSeqStringTag) {
+      start = SeqAsciiString::cast(string)->GetChars();
+    } else {
+      start = ExternalAsciiString::cast(string)->resource()->data();
+    }
+    return FlatContent(Vector<const char>(start + offset, length));
+  } else {
+    ASSERT(shape.encoding_tag() == kTwoByteStringTag);
+    const uc16* start;
+    if (shape.representation_tag() == kSeqStringTag) {
+      start = SeqTwoByteString::cast(string)->GetChars();
+    } else {
+      start = ExternalTwoByteString::cast(string)->resource()->data();
+    }
+    return FlatContent(Vector<const uc16>(start + offset, length));
+  }
 }
 
 
@@ -5290,13 +5167,17 @@
 
 
 const uc16* String::GetTwoByteData(unsigned start) {
-  ASSERT(!IsAsciiRepresentation());
+  ASSERT(!IsAsciiRepresentationUnderneath());
   switch (StringShape(this).representation_tag()) {
     case kSeqStringTag:
       return SeqTwoByteString::cast(this)->SeqTwoByteStringGetData(start);
     case kExternalStringTag:
       return ExternalTwoByteString::cast(this)->
         ExternalTwoByteStringGetData(start);
+    case kSlicedStringTag: {
+      SlicedString* slice = SlicedString::cast(this);
+      return slice->parent()->GetTwoByteData(start + slice->offset());
+    }
     case kConsStringTag:
       UNREACHABLE();
       return NULL;
@@ -5587,6 +5468,10 @@
                                                      max_chars);
         return rbb->util_buffer;
       }
+    case kSlicedStringTag:
+      return SlicedString::cast(input)->SlicedStringReadBlock(rbb,
+                                                              offset_ptr,
+                                                              max_chars);
     default:
       break;
   }
@@ -5669,11 +5554,13 @@
   if (str_ == NULL) return;
   Handle<String> str(str_);
   ASSERT(str->IsFlat());
-  is_ascii_ = str->IsAsciiRepresentation();
+  String::FlatContent content = str->GetFlatContent();
+  ASSERT(content.IsFlat());
+  is_ascii_ = content.IsAscii();
   if (is_ascii_) {
-    start_ = str->ToAsciiVector().start();
+    start_ = content.ToAsciiVector().start();
   } else {
-    start_ = str->ToUC16Vector().start();
+    start_ = content.ToUC16Vector().start();
   }
 }
 
@@ -5728,6 +5615,11 @@
                                                      max_chars);
        }
        return;
+    case kSlicedStringTag:
+      SlicedString::cast(input)->SlicedStringReadBlockIntoBuffer(rbb,
+                                                                 offset_ptr,
+                                                                 max_chars);
+      return;
     default:
       break;
   }
@@ -5862,6 +5754,31 @@
 }
 
 
+uint16_t SlicedString::SlicedStringGet(int index) {
+  return parent()->Get(offset() + index);
+}
+
+
+const unibrow::byte* SlicedString::SlicedStringReadBlock(
+    ReadBlockBuffer* buffer, unsigned* offset_ptr, unsigned chars) {
+  unsigned offset = this->offset();
+  *offset_ptr += offset;
+  const unibrow::byte* answer = String::ReadBlock(String::cast(parent()),
+                                                  buffer, offset_ptr, chars);
+  *offset_ptr -= offset;
+  return answer;
+}
+
+
+void SlicedString::SlicedStringReadBlockIntoBuffer(
+    ReadBlockBuffer* buffer, unsigned* offset_ptr, unsigned chars) {
+  unsigned offset = this->offset();
+  *offset_ptr += offset;
+  String::ReadBlockIntoBuffer(String::cast(parent()),
+                              buffer, offset_ptr, chars);
+  *offset_ptr -= offset;
+}
+
 template <typename sinkchar>
 void String::WriteToFlat(String* src,
                          sinkchar* sink,
@@ -5929,6 +5846,13 @@
         }
         break;
       }
+      case kAsciiStringTag | kSlicedStringTag:
+      case kTwoByteStringTag | kSlicedStringTag: {
+        SlicedString* slice = SlicedString::cast(source);
+        unsigned offset = slice->offset();
+        WriteToFlat(slice->parent(), sink, from + offset, to + offset);
+        return;
+      }
     }
   }
 }
@@ -5993,12 +5917,13 @@
 static inline bool CompareStringContentsPartial(Isolate* isolate,
                                                 IteratorA* ia,
                                                 String* b) {
-  if (b->IsFlat()) {
-    if (b->IsAsciiRepresentation()) {
-      VectorIterator<char> ib(b->ToAsciiVector());
+  String::FlatContent content = b->GetFlatContent();
+  if (content.IsFlat()) {
+    if (content.IsAscii()) {
+      VectorIterator<char> ib(content.ToAsciiVector());
       return CompareStringContents(ia, &ib);
     } else {
-      VectorIterator<uc16> ib(b->ToUC16Vector());
+      VectorIterator<uc16> ib(content.ToUC16Vector());
       return CompareStringContents(ia, &ib);
     }
   } else {
@@ -6037,16 +5962,18 @@
   }
 
   Isolate* isolate = GetIsolate();
-  if (lhs->IsFlat()) {
-    if (lhs->IsAsciiRepresentation()) {
-      Vector<const char> vec1 = lhs->ToAsciiVector();
-      if (rhs->IsFlat()) {
-        if (rhs->IsAsciiRepresentation()) {
-          Vector<const char> vec2 = rhs->ToAsciiVector();
+  String::FlatContent lhs_content = lhs->GetFlatContent();
+  String::FlatContent rhs_content = rhs->GetFlatContent();
+  if (lhs_content.IsFlat()) {
+    if (lhs_content.IsAscii()) {
+      Vector<const char> vec1 = lhs_content.ToAsciiVector();
+      if (rhs_content.IsFlat()) {
+        if (rhs_content.IsAscii()) {
+          Vector<const char> vec2 = rhs_content.ToAsciiVector();
           return CompareRawStringContents(vec1, vec2);
         } else {
           VectorIterator<char> buf1(vec1);
-          VectorIterator<uc16> ib(rhs->ToUC16Vector());
+          VectorIterator<uc16> ib(rhs_content.ToUC16Vector());
           return CompareStringContents(&buf1, &ib);
         }
       } else {
@@ -6056,14 +5983,14 @@
             isolate->objects_string_compare_buffer_b());
       }
     } else {
-      Vector<const uc16> vec1 = lhs->ToUC16Vector();
-      if (rhs->IsFlat()) {
-        if (rhs->IsAsciiRepresentation()) {
+      Vector<const uc16> vec1 = lhs_content.ToUC16Vector();
+      if (rhs_content.IsFlat()) {
+        if (rhs_content.IsAscii()) {
           VectorIterator<uc16> buf1(vec1);
-          VectorIterator<char> ib(rhs->ToAsciiVector());
+          VectorIterator<char> ib(rhs_content.ToAsciiVector());
           return CompareStringContents(&buf1, &ib);
         } else {
-          Vector<const uc16> vec2(rhs->ToUC16Vector());
+          Vector<const uc16> vec2(rhs_content.ToUC16Vector());
           return CompareRawStringContents(vec1, vec2);
         }
       } else {
@@ -6116,8 +6043,10 @@
 bool String::IsAsciiEqualTo(Vector<const char> str) {
   int slen = length();
   if (str.length() != slen) return false;
-  if (IsFlat() && IsAsciiRepresentation()) {
-    return CompareChars(ToAsciiVector().start(), str.start(), slen) == 0;
+  FlatContent content = GetFlatContent();
+  if (content.IsAscii()) {
+    return CompareChars(content.ToAsciiVector().start(),
+                        str.start(), slen) == 0;
   }
   for (int i = 0; i < slen; i++) {
     if (Get(i) != static_cast<uint16_t>(str[i])) return false;
@@ -6129,8 +6058,9 @@
 bool String::IsTwoByteEqualTo(Vector<const uc16> str) {
   int slen = length();
   if (str.length() != slen) return false;
-  if (IsFlat() && IsTwoByteRepresentation()) {
-    return CompareChars(ToUC16Vector().start(), str.start(), slen) == 0;
+  FlatContent content = GetFlatContent();
+  if (content.IsTwoByte()) {
+    return CompareChars(content.ToUC16Vector().start(), str.start(), slen) == 0;
   }
   for (int i = 0; i < slen; i++) {
     if (Get(i) != str[i]) return false;
@@ -7060,126 +6990,99 @@
   PrintF(out, "Deoptimization Input Data (deopt points = %d)\n", deopt_count);
   if (0 == deopt_count) return;
 
-  PrintF(out, "%6s  %6s  %6s  %12s\n", "index", "ast id", "argc", "commands");
+  PrintF(out, "%6s  %6s  %6s  %12s\n", "index", "ast id", "argc",
+         FLAG_print_code_verbose ? "commands" : "");
   for (int i = 0; i < deopt_count; i++) {
-    int command_count = 0;
     PrintF(out, "%6d  %6d  %6d",
            i, AstId(i)->value(), ArgumentsStackHeight(i)->value());
+
+    if (!FLAG_print_code_verbose) {
+      PrintF(out, "\n");
+      continue;
+    }
+    // Print details of the frame translation.
     int translation_index = TranslationIndex(i)->value();
     TranslationIterator iterator(TranslationByteArray(), translation_index);
     Translation::Opcode opcode =
         static_cast<Translation::Opcode>(iterator.Next());
     ASSERT(Translation::BEGIN == opcode);
     int frame_count = iterator.Next();
-    if (FLAG_print_code_verbose) {
-      PrintF(out, "  %s {count=%d}\n", Translation::StringFor(opcode),
-             frame_count);
-    }
+    PrintF(out, "  %s {count=%d}\n", Translation::StringFor(opcode),
+           frame_count);
 
-    for (int i = 0; i < frame_count; ++i) {
-      opcode = static_cast<Translation::Opcode>(iterator.Next());
-      ASSERT(Translation::FRAME == opcode);
-      int ast_id = iterator.Next();
-      int function_id = iterator.Next();
-      JSFunction* function =
-          JSFunction::cast(LiteralArray()->get(function_id));
-      unsigned height = iterator.Next();
-      if (FLAG_print_code_verbose) {
-        PrintF(out, "%24s  %s {ast_id=%d, function=",
-               "", Translation::StringFor(opcode), ast_id);
-        function->PrintName(out);
-        PrintF(out, ", height=%u}\n", height);
+    while (iterator.HasNext() &&
+           Translation::BEGIN !=
+           (opcode = static_cast<Translation::Opcode>(iterator.Next()))) {
+      PrintF(out, "%24s    %s ", "", Translation::StringFor(opcode));
+
+      switch (opcode) {
+        case Translation::BEGIN:
+          UNREACHABLE();
+          break;
+
+        case Translation::FRAME: {
+          int ast_id = iterator.Next();
+          int function_id = iterator.Next();
+          JSFunction* function =
+              JSFunction::cast(LiteralArray()->get(function_id));
+          unsigned height = iterator.Next();
+          PrintF(out, "{ast_id=%d, \nfunction=", ast_id);
+          function->PrintName(out);
+          PrintF(out, ", height=%u}", height);
+          break;
+        }
+
+        case Translation::DUPLICATE:
+          break;
+
+        case Translation::REGISTER: {
+          int reg_code = iterator.Next();
+            PrintF(out, "{input=%s}", converter.NameOfCPURegister(reg_code));
+          break;
+        }
+
+        case Translation::INT32_REGISTER: {
+          int reg_code = iterator.Next();
+          PrintF(out, "{input=%s}", converter.NameOfCPURegister(reg_code));
+          break;
+        }
+
+        case Translation::DOUBLE_REGISTER: {
+          int reg_code = iterator.Next();
+          PrintF(out, "{input=%s}",
+                 DoubleRegister::AllocationIndexToString(reg_code));
+          break;
+        }
+
+        case Translation::STACK_SLOT: {
+          int input_slot_index = iterator.Next();
+          PrintF(out, "{input=%d}", input_slot_index);
+          break;
+        }
+
+        case Translation::INT32_STACK_SLOT: {
+          int input_slot_index = iterator.Next();
+          PrintF(out, "{input=%d}", input_slot_index);
+          break;
+        }
+
+        case Translation::DOUBLE_STACK_SLOT: {
+          int input_slot_index = iterator.Next();
+          PrintF(out, "{input=%d}", input_slot_index);
+          break;
+        }
+
+        case Translation::LITERAL: {
+          unsigned literal_index = iterator.Next();
+          PrintF(out, "{literal_id=%u}", literal_index);
+          break;
+        }
+
+        case Translation::ARGUMENTS_OBJECT:
+          break;
       }
-
-      // Size of translation is height plus all incoming arguments including
-      // receiver.
-      int size = height + function->shared()->formal_parameter_count() + 1;
-      command_count += size;
-      for (int j = 0; j < size; ++j) {
-        opcode = static_cast<Translation::Opcode>(iterator.Next());
-        if (FLAG_print_code_verbose) {
-          PrintF(out, "%24s    %s ", "", Translation::StringFor(opcode));
-        }
-
-        if (opcode == Translation::DUPLICATE) {
-          opcode = static_cast<Translation::Opcode>(iterator.Next());
-          if (FLAG_print_code_verbose) {
-            PrintF(out, "%s ", Translation::StringFor(opcode));
-          }
-          --j;  // Two commands share the same frame index.
-        }
-
-        switch (opcode) {
-          case Translation::BEGIN:
-          case Translation::FRAME:
-          case Translation::DUPLICATE:
-            UNREACHABLE();
-            break;
-
-          case Translation::REGISTER: {
-            int reg_code = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{input=%s}", converter.NameOfCPURegister(reg_code));
-            }
-            break;
-          }
-
-          case Translation::INT32_REGISTER: {
-            int reg_code = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{input=%s}", converter.NameOfCPURegister(reg_code));
-            }
-            break;
-          }
-
-          case Translation::DOUBLE_REGISTER: {
-            int reg_code = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{input=%s}",
-                     DoubleRegister::AllocationIndexToString(reg_code));
-            }
-            break;
-          }
-
-          case Translation::STACK_SLOT: {
-            int input_slot_index = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{input=%d}", input_slot_index);
-            }
-            break;
-          }
-
-          case Translation::INT32_STACK_SLOT: {
-            int input_slot_index = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{input=%d}", input_slot_index);
-            }
-            break;
-          }
-
-          case Translation::DOUBLE_STACK_SLOT: {
-            int input_slot_index = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{input=%d}", input_slot_index);
-            }
-            break;
-          }
-
-          case Translation::LITERAL: {
-            unsigned literal_index = iterator.Next();
-            if (FLAG_print_code_verbose)  {
-              PrintF(out, "{literal_id=%u}", literal_index);
-            }
-            break;
-          }
-
-          case Translation::ARGUMENTS_OBJECT:
-            break;
-        }
-        if (FLAG_print_code_verbose) PrintF(out, "\n");
-      }
+      PrintF(out, "\n");
     }
-    if (!FLAG_print_code_verbose) PrintF(out, "  %12d\n", command_count);
   }
 }
 
@@ -7217,6 +7120,7 @@
     case UNARY_OP_IC: return "UNARY_OP_IC";
     case BINARY_OP_IC: return "BINARY_OP_IC";
     case COMPARE_IC: return "COMPARE_IC";
+    case TO_BOOLEAN_IC: return "TO_BOOLEAN_IC";
   }
   UNREACHABLE();
   return NULL;
@@ -7455,7 +7359,8 @@
           // exceed the capacity of new space, and we would fail repeatedly
           // trying to convert the FixedDoubleArray.
           MaybeObject* maybe_value_object =
-              GetHeap()->AllocateHeapNumber(old_elements->get(i), TENURED);
+              GetHeap()->AllocateHeapNumber(old_elements->get_scalar(i),
+                                            TENURED);
           if (!maybe_value_object->ToObject(&obj)) return maybe_value_object;
           // Force write barrier. It's not worth trying to exploit
           // elems->GetWriteBarrierMode(), since it requires an
@@ -7549,9 +7454,10 @@
 
   switch (GetElementsKind()) {
     case FAST_ELEMENTS: {
+    case FAST_DOUBLE_ELEMENTS:
       // Make sure we never try to shrink dense arrays into sparse arrays.
-      ASSERT(static_cast<uint32_t>(FixedArray::cast(elements())->length()) <=
-                                   new_length);
+      ASSERT(static_cast<uint32_t>(
+          FixedArrayBase::cast(elements())->length()) <= new_length);
       MaybeObject* result = NormalizeElements();
       if (result->IsFailure()) return result;
 
@@ -7580,7 +7486,6 @@
     case EXTERNAL_FLOAT_ELEMENTS:
     case EXTERNAL_DOUBLE_ELEMENTS:
     case EXTERNAL_PIXEL_ELEMENTS:
-    case FAST_DOUBLE_ELEMENTS:
       UNREACHABLE();
       break;
   }
@@ -7695,8 +7600,7 @@
         }
         int min = NewElementsCapacity(old_capacity);
         int new_capacity = value > min ? value : min;
-        if (new_capacity <= kMaxFastElementsLength ||
-            !ShouldConvertToSlowElements(new_capacity)) {
+        if (!ShouldConvertToSlowElements(new_capacity)) {
           MaybeObject* result;
           if (GetElementsKind() == FAST_ELEMENTS) {
             result = SetFastElementsCapacityAndLength(new_capacity, value);
@@ -7922,6 +7826,17 @@
       }
       break;
     }
+    case FAST_DOUBLE_ELEMENTS: {
+      uint32_t length = IsJSArray() ?
+          static_cast<uint32_t>
+              (Smi::cast(JSArray::cast(this)->length())->value()) :
+          static_cast<uint32_t>(FixedDoubleArray::cast(elements())->length());
+      if ((index < length) &&
+          !FixedDoubleArray::cast(elements())->is_the_hole(index)) {
+        return true;
+      }
+      break;
+    }
     case EXTERNAL_PIXEL_ELEMENTS: {
       ExternalPixelArray* pixels = ExternalPixelArray::cast(elements());
       if (index < static_cast<uint32_t>(pixels->length())) {
@@ -7936,8 +7851,7 @@
     case EXTERNAL_INT_ELEMENTS:
     case EXTERNAL_UNSIGNED_INT_ELEMENTS:
     case EXTERNAL_FLOAT_ELEMENTS:
-    case EXTERNAL_DOUBLE_ELEMENTS:
-    case FAST_DOUBLE_ELEMENTS: {
+    case EXTERNAL_DOUBLE_ELEMENTS: {
       ExternalArray* array = ExternalArray::cast(elements());
       if (index < static_cast<uint32_t>(array->length())) {
         return true;
@@ -8048,6 +7962,17 @@
       }
       break;
     }
+    case FAST_DOUBLE_ELEMENTS: {
+      uint32_t length = IsJSArray() ?
+          static_cast<uint32_t>
+              (Smi::cast(JSArray::cast(this)->length())->value()) :
+          static_cast<uint32_t>(FixedDoubleArray::cast(elements())->length());
+      if ((index < length) &&
+          !FixedDoubleArray::cast(elements())->is_the_hole(index)) {
+        return FAST_ELEMENT;
+      }
+      break;
+    }
     case EXTERNAL_PIXEL_ELEMENTS: {
       ExternalPixelArray* pixels = ExternalPixelArray::cast(elements());
       if (index < static_cast<uint32_t>(pixels->length())) return FAST_ELEMENT;
@@ -8065,9 +7990,6 @@
       if (index < static_cast<uint32_t>(array->length())) return FAST_ELEMENT;
       break;
     }
-    case FAST_DOUBLE_ELEMENTS:
-      UNREACHABLE();
-      break;
     case DICTIONARY_ELEMENTS: {
       if (element_dictionary()->FindEntry(index) !=
           NumberDictionary::kNotFound) {
@@ -8434,8 +8356,7 @@
   if ((index - length) < kMaxGap) {
     // Try allocating extra space.
     int new_capacity = NewElementsCapacity(index + 1);
-    if (new_capacity <= kMaxFastElementsLength ||
-        !ShouldConvertToSlowElements(new_capacity)) {
+    if (!ShouldConvertToSlowElements(new_capacity)) {
       ASSERT(static_cast<uint32_t>(new_capacity) > index);
       Object* new_elements;
       MaybeObject* maybe =
@@ -8515,14 +8436,14 @@
         return isolate->Throw(*error);
       }
     }
-    Object* new_dictionary;
+    FixedArrayBase* new_dictionary;
     MaybeObject* maybe = dictionary->AtNumberPut(index, value);
-    if (!maybe->ToObject(&new_dictionary)) return maybe;
+    if (!maybe->To<FixedArrayBase>(&new_dictionary)) return maybe;
     if (dictionary != NumberDictionary::cast(new_dictionary)) {
       if (is_arguments) {
         elements->set(1, new_dictionary);
       } else {
-        set_elements(HeapObject::cast(new_dictionary));
+        set_elements(new_dictionary);
       }
       dictionary = NumberDictionary::cast(new_dictionary);
     }
@@ -8543,7 +8464,7 @@
     } else {
       new_length = dictionary->max_number_key() + 1;
     }
-    MaybeObject* result = ShouldConvertToFastDoubleElements()
+    MaybeObject* result = CanConvertToFastDoubleElements()
         ? SetFastDoubleElementsCapacityAndLength(new_length, new_length)
         : SetFastElementsCapacityAndLength(new_length, new_length);
     if (result->IsFailure()) return result;
@@ -8617,8 +8538,7 @@
   if ((index - elms_length) < kMaxGap) {
     // Try allocating extra space.
     int new_capacity = NewElementsCapacity(index+1);
-    if (new_capacity <= kMaxFastElementsLength ||
-        !ShouldConvertToSlowElements(new_capacity)) {
+    if (!ShouldConvertToSlowElements(new_capacity)) {
       ASSERT(static_cast<uint32_t>(new_capacity) > index);
       Object* obj;
       { MaybeObject* maybe_obj =
@@ -8783,71 +8703,6 @@
 }
 
 
-MaybeObject* JSObject::GetElementPostInterceptor(Object* receiver,
-                                                 uint32_t index) {
-  // Get element works for both JSObject and JSArray since
-  // JSArray::length cannot change.
-  switch (GetElementsKind()) {
-    case FAST_ELEMENTS: {
-      FixedArray* elms = FixedArray::cast(elements());
-      if (index < static_cast<uint32_t>(elms->length())) {
-        Object* value = elms->get(index);
-        if (!value->IsTheHole()) return value;
-      }
-      break;
-    }
-    case FAST_DOUBLE_ELEMENTS: {
-      FixedDoubleArray* elms = FixedDoubleArray::cast(elements());
-      if (index < static_cast<uint32_t>(elms->length())) {
-        if (!elms->is_the_hole(index)) {
-          return GetHeap()->NumberFromDouble(elms->get(index));
-        }
-      }
-      break;
-    }
-    case EXTERNAL_PIXEL_ELEMENTS:
-    case EXTERNAL_BYTE_ELEMENTS:
-    case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-    case EXTERNAL_SHORT_ELEMENTS:
-    case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-    case EXTERNAL_INT_ELEMENTS:
-    case EXTERNAL_UNSIGNED_INT_ELEMENTS:
-    case EXTERNAL_FLOAT_ELEMENTS:
-    case EXTERNAL_DOUBLE_ELEMENTS: {
-      MaybeObject* maybe_value = GetExternalElement(index);
-      Object* value;
-      if (!maybe_value->ToObject(&value)) return maybe_value;
-      if (!value->IsUndefined()) return value;
-      break;
-    }
-    case DICTIONARY_ELEMENTS: {
-      NumberDictionary* dictionary = element_dictionary();
-      int entry = dictionary->FindEntry(index);
-      if (entry != NumberDictionary::kNotFound) {
-        Object* element = dictionary->ValueAt(entry);
-        PropertyDetails details = dictionary->DetailsAt(entry);
-        if (details.type() == CALLBACKS) {
-          return GetElementWithCallback(receiver,
-                                        element,
-                                        index,
-                                        this);
-        }
-        return element;
-      }
-      break;
-    }
-    case NON_STRICT_ARGUMENTS_ELEMENTS:
-      UNIMPLEMENTED();
-      break;
-  }
-
-  // Continue searching via the prototype chain.
-  Object* pt = GetPrototype();
-  if (pt->IsNull()) return GetHeap()->undefined_value();
-  return pt->GetElementWithReceiver(receiver, index);
-}
-
-
 MaybeObject* JSObject::GetElementWithInterceptor(Object* receiver,
                                                  uint32_t index) {
   Isolate* isolate = GetIsolate();
@@ -8875,218 +8730,33 @@
     if (!result.IsEmpty()) return *v8::Utils::OpenHandle(*result);
   }
 
-  MaybeObject* raw_result =
-      holder_handle->GetElementPostInterceptor(*this_handle, index);
+  Heap* heap = holder_handle->GetHeap();
+  ElementsAccessor* handler = holder_handle->GetElementsAccessor();
+  MaybeObject* raw_result = handler->Get(holder_handle->elements(),
+                                         index,
+                                         *holder_handle,
+                                         *this_handle);
+  if (raw_result != heap->the_hole_value()) return raw_result;
+
   RETURN_IF_SCHEDULED_EXCEPTION(isolate);
-  return raw_result;
-}
 
-
-MaybeObject* JSObject::GetElementWithReceiver(Object* receiver,
-                                              uint32_t index) {
-  // Check access rights if needed.
-  if (IsAccessCheckNeeded()) {
-    Heap* heap = GetHeap();
-    if (!heap->isolate()->MayIndexedAccess(this, index, v8::ACCESS_GET)) {
-      heap->isolate()->ReportFailedAccessCheck(this, v8::ACCESS_GET);
-      return heap->undefined_value();
-    }
-  }
-
-  if (HasIndexedInterceptor()) {
-    return GetElementWithInterceptor(receiver, index);
-  }
-
-  // Get element works for both JSObject and JSArray since
-  // JSArray::length cannot change.
-  switch (GetElementsKind()) {
-    case FAST_ELEMENTS: {
-      FixedArray* elms = FixedArray::cast(elements());
-      if (index < static_cast<uint32_t>(elms->length())) {
-        Object* value = elms->get(index);
-        if (!value->IsTheHole()) return value;
-      }
-      break;
-    }
-    case FAST_DOUBLE_ELEMENTS: {
-      FixedDoubleArray* elms = FixedDoubleArray::cast(elements());
-      if (index < static_cast<uint32_t>(elms->length())) {
-        if (!elms->is_the_hole(index)) {
-          double double_value = elms->get(index);
-          return GetHeap()->NumberFromDouble(double_value);
-        }
-      }
-      break;
-    }
-    case EXTERNAL_PIXEL_ELEMENTS:
-    case EXTERNAL_BYTE_ELEMENTS:
-    case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
-    case EXTERNAL_SHORT_ELEMENTS:
-    case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
-    case EXTERNAL_INT_ELEMENTS:
-    case EXTERNAL_UNSIGNED_INT_ELEMENTS:
-    case EXTERNAL_FLOAT_ELEMENTS:
-    case EXTERNAL_DOUBLE_ELEMENTS: {
-      MaybeObject* maybe_value = GetExternalElement(index);
-      Object* value;
-      if (!maybe_value->ToObject(&value)) return maybe_value;
-      if (!value->IsUndefined()) return value;
-      break;
-    }
-    case DICTIONARY_ELEMENTS: {
-      NumberDictionary* dictionary = element_dictionary();
-      int entry = dictionary->FindEntry(index);
-      if (entry != NumberDictionary::kNotFound) {
-        Object* element = dictionary->ValueAt(entry);
-        PropertyDetails details = dictionary->DetailsAt(entry);
-        if (details.type() == CALLBACKS) {
-          return GetElementWithCallback(receiver,
-                                        element,
-                                        index,
-                                        this);
-        }
-        return element;
-      }
-      break;
-    }
-    case NON_STRICT_ARGUMENTS_ELEMENTS: {
-      FixedArray* parameter_map = FixedArray::cast(elements());
-      uint32_t length = parameter_map->length();
-      Object* probe =
-          (index < length - 2) ? parameter_map->get(index + 2) : NULL;
-      if (probe != NULL && !probe->IsTheHole()) {
-        Context* context = Context::cast(parameter_map->get(0));
-        int context_index = Smi::cast(probe)->value();
-        ASSERT(!context->get(context_index)->IsTheHole());
-        return context->get(context_index);
-      } else {
-        // Object is not mapped, defer to the arguments.
-        FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
-        if (arguments->IsDictionary()) {
-          NumberDictionary* dictionary = NumberDictionary::cast(arguments);
-          int entry = dictionary->FindEntry(index);
-          if (entry != NumberDictionary::kNotFound) {
-            Object* element = dictionary->ValueAt(entry);
-            PropertyDetails details = dictionary->DetailsAt(entry);
-            if (details.type() == CALLBACKS) {
-              return GetElementWithCallback(receiver,
-                                            element,
-                                            index,
-                                            this);
-            }
-            return element;
-          }
-        } else if (index < static_cast<uint32_t>(arguments->length())) {
-          Object* value = arguments->get(index);
-          if (!value->IsTheHole()) return value;
-        }
-      }
-      break;
-    }
-  }
-
-  Object* pt = GetPrototype();
-  Heap* heap = GetHeap();
+  Object* pt = holder_handle->GetPrototype();
   if (pt == heap->null_value()) return heap->undefined_value();
-  return pt->GetElementWithReceiver(receiver, index);
-}
-
-
-MaybeObject* JSObject::GetExternalElement(uint32_t index) {
-  // Get element works for both JSObject and JSArray since
-  // JSArray::length cannot change.
-  switch (GetElementsKind()) {
-    case EXTERNAL_PIXEL_ELEMENTS: {
-      ExternalPixelArray* pixels = ExternalPixelArray::cast(elements());
-      if (index < static_cast<uint32_t>(pixels->length())) {
-        uint8_t value = pixels->get(index);
-        return Smi::FromInt(value);
-      }
-      break;
-    }
-    case EXTERNAL_BYTE_ELEMENTS: {
-      ExternalByteArray* array = ExternalByteArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        int8_t value = array->get(index);
-        return Smi::FromInt(value);
-      }
-      break;
-    }
-    case EXTERNAL_UNSIGNED_BYTE_ELEMENTS: {
-      ExternalUnsignedByteArray* array =
-          ExternalUnsignedByteArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        uint8_t value = array->get(index);
-        return Smi::FromInt(value);
-      }
-      break;
-    }
-    case EXTERNAL_SHORT_ELEMENTS: {
-      ExternalShortArray* array = ExternalShortArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        int16_t value = array->get(index);
-        return Smi::FromInt(value);
-      }
-      break;
-    }
-    case EXTERNAL_UNSIGNED_SHORT_ELEMENTS: {
-      ExternalUnsignedShortArray* array =
-          ExternalUnsignedShortArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        uint16_t value = array->get(index);
-        return Smi::FromInt(value);
-      }
-      break;
-    }
-    case EXTERNAL_INT_ELEMENTS: {
-      ExternalIntArray* array = ExternalIntArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        int32_t value = array->get(index);
-        return GetHeap()->NumberFromInt32(value);
-      }
-      break;
-    }
-    case EXTERNAL_UNSIGNED_INT_ELEMENTS: {
-      ExternalUnsignedIntArray* array =
-          ExternalUnsignedIntArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        uint32_t value = array->get(index);
-        return GetHeap()->NumberFromUint32(value);
-      }
-      break;
-    }
-    case EXTERNAL_FLOAT_ELEMENTS: {
-      ExternalFloatArray* array = ExternalFloatArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        float value = array->get(index);
-        return GetHeap()->AllocateHeapNumber(value);
-      }
-      break;
-    }
-    case EXTERNAL_DOUBLE_ELEMENTS: {
-      ExternalDoubleArray* array = ExternalDoubleArray::cast(elements());
-      if (index < static_cast<uint32_t>(array->length())) {
-        double value = array->get(index);
-        return GetHeap()->AllocateHeapNumber(value);
-      }
-      break;
-    }
-    case FAST_DOUBLE_ELEMENTS:
-    case FAST_ELEMENTS:
-    case DICTIONARY_ELEMENTS:
-      UNREACHABLE();
-      break;
-    case NON_STRICT_ARGUMENTS_ELEMENTS:
-      UNIMPLEMENTED();
-      break;
-  }
-  return GetHeap()->undefined_value();
+  return pt->GetElementWithReceiver(*this_handle, index);
 }
 
 
 bool JSObject::HasDenseElements() {
   int capacity = 0;
-  int number_of_elements = 0;
+  int used = 0;
+  GetElementsCapacityAndUsage(&capacity, &used);
+  return (capacity == 0) || (used > (capacity / 2));
+}
+
+
+void JSObject::GetElementsCapacityAndUsage(int* capacity, int* used) {
+  *capacity = 0;
+  *used = 0;
 
   FixedArrayBase* backing_store_base = FixedArrayBase::cast(elements());
   FixedArray* backing_store = NULL;
@@ -9097,34 +8767,33 @@
       backing_store = FixedArray::cast(backing_store_base);
       if (backing_store->IsDictionary()) {
         NumberDictionary* dictionary = NumberDictionary::cast(backing_store);
-        capacity = dictionary->Capacity();
-        number_of_elements = dictionary->NumberOfElements();
+        *capacity = dictionary->Capacity();
+        *used = dictionary->NumberOfElements();
         break;
       }
       // Fall through.
     case FAST_ELEMENTS:
       backing_store = FixedArray::cast(backing_store_base);
-      capacity = backing_store->length();
-      for (int i = 0; i < capacity; ++i) {
-        if (!backing_store->get(i)->IsTheHole()) ++number_of_elements;
+      *capacity = backing_store->length();
+      for (int i = 0; i < *capacity; ++i) {
+        if (!backing_store->get(i)->IsTheHole()) ++(*used);
       }
       break;
     case DICTIONARY_ELEMENTS: {
       NumberDictionary* dictionary =
           NumberDictionary::cast(FixedArray::cast(elements()));
-      capacity = dictionary->Capacity();
-      number_of_elements = dictionary->NumberOfElements();
+      *capacity = dictionary->Capacity();
+      *used = dictionary->NumberOfElements();
       break;
     }
     case FAST_DOUBLE_ELEMENTS: {
       FixedDoubleArray* elms = FixedDoubleArray::cast(elements());
-      capacity = elms->length();
-      for (int i = 0; i < capacity; i++) {
-        if (!elms->is_the_hole(i)) number_of_elements++;
+      *capacity = elms->length();
+      for (int i = 0; i < *capacity; i++) {
+        if (!elms->is_the_hole(i)) ++(*used);
       }
       break;
     }
-    case EXTERNAL_PIXEL_ELEMENTS:
     case EXTERNAL_BYTE_ELEMENTS:
     case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
     case EXTERNAL_SHORT_ELEMENTS:
@@ -9132,30 +8801,34 @@
     case EXTERNAL_INT_ELEMENTS:
     case EXTERNAL_UNSIGNED_INT_ELEMENTS:
     case EXTERNAL_FLOAT_ELEMENTS:
-    case EXTERNAL_DOUBLE_ELEMENTS: {
-      return true;
-    }
+    case EXTERNAL_DOUBLE_ELEMENTS:
+    case EXTERNAL_PIXEL_ELEMENTS:
+      // External arrays are considered 100% used.
+      ExternalArray* external_array = ExternalArray::cast(elements());
+      *capacity = external_array->length();
+      *used = external_array->length();
+      break;
   }
-  return (capacity == 0) || (number_of_elements > (capacity / 2));
 }
 
 
 bool JSObject::ShouldConvertToSlowElements(int new_capacity) {
-  // Keep the array in fast case if the current backing storage is
-  // almost filled and if the new capacity is no more than twice the
-  // old capacity.
-  int elements_length = 0;
-  if (elements()->map() == GetHeap()->non_strict_arguments_elements_map()) {
-    FixedArray* backing_store = FixedArray::cast(elements());
-    elements_length = FixedArray::cast(backing_store->get(1))->length();
-  } else if (HasFastElements()) {
-    elements_length = FixedArray::cast(elements())->length();
-  } else if (HasFastDoubleElements()) {
-    elements_length = FixedDoubleArray::cast(elements())->length();
-  } else {
-    UNREACHABLE();
+  STATIC_ASSERT(kMaxUncheckedOldFastElementsLength <=
+                kMaxUncheckedFastElementsLength);
+  if (new_capacity <= kMaxUncheckedOldFastElementsLength ||
+      (new_capacity <= kMaxUncheckedFastElementsLength &&
+       GetHeap()->InNewSpace(this))) {
+    return false;
   }
-  return !HasDenseElements() || ((new_capacity / 2) > elements_length);
+  // If the fast-case backing storage takes up roughly three times as
+  // much space (in machine words) as a dictionary backing storage
+  // would, the object should have slow elements.
+  int old_capacity = 0;
+  int used_elements = 0;
+  GetElementsCapacityAndUsage(&old_capacity, &used_elements);
+  int dictionary_size = NumberDictionary::ComputeCapacity(used_elements) *
+      NumberDictionary::kEntrySize;
+  return 3 * dictionary_size <= new_capacity;
 }
 
 
@@ -9178,20 +8851,21 @@
   // dictionary, we cannot go back to fast case.
   if (dictionary->requires_slow_elements()) return false;
   // If the dictionary backing storage takes up roughly half as much
-  // space as a fast-case backing storage would the array should have
-  // fast elements.
-  uint32_t length = 0;
+  // space (in machine words) as a fast-case backing storage would,
+  // the object should have fast elements.
+  uint32_t array_size = 0;
   if (IsJSArray()) {
-    CHECK(JSArray::cast(this)->length()->ToArrayIndex(&length));
+    CHECK(JSArray::cast(this)->length()->ToArrayIndex(&array_size));
   } else {
-    length = dictionary->max_number_key();
+    array_size = dictionary->max_number_key();
   }
-  return static_cast<uint32_t>(dictionary->Capacity()) >=
-      (length / (2 * NumberDictionary::kEntrySize));
+  uint32_t dictionary_size = static_cast<uint32_t>(dictionary->Capacity()) *
+      NumberDictionary::kEntrySize;
+  return 2 * dictionary_size >= array_size;
 }
 
 
-bool JSObject::ShouldConvertToFastDoubleElements() {
+bool JSObject::CanConvertToFastDoubleElements() {
   if (FLAG_unbox_double_arrays) {
     ASSERT(HasDictionaryElements());
     NumberDictionary* dictionary = NumberDictionary::cast(elements());
@@ -9381,6 +9055,15 @@
       return (index < length) &&
           !FixedArray::cast(elements())->get(index)->IsTheHole();
     }
+    case FAST_DOUBLE_ELEMENTS: {
+      uint32_t length = IsJSArray() ?
+          static_cast<uint32_t>(
+              Smi::cast(JSArray::cast(this)->length())->value()) :
+          static_cast<uint32_t>(FixedDoubleArray::cast(elements())->length());
+      return (index < length) &&
+          !FixedDoubleArray::cast(elements())->is_the_hole(index);
+      break;
+    }
     case EXTERNAL_PIXEL_ELEMENTS: {
       ExternalPixelArray* pixels = ExternalPixelArray::cast(elements());
       return index < static_cast<uint32_t>(pixels->length());
@@ -9396,9 +9079,6 @@
       ExternalArray* array = ExternalArray::cast(elements());
       return index < static_cast<uint32_t>(array->length());
     }
-    case FAST_DOUBLE_ELEMENTS:
-      UNREACHABLE();
-      break;
     case DICTIONARY_ELEMENTS: {
       return element_dictionary()->FindEntry(index)
           != NumberDictionary::kNotFound;
@@ -10118,11 +9798,8 @@
 template<typename Shape, typename Key>
 MaybeObject* HashTable<Shape, Key>::Allocate(int at_least_space_for,
                                              PretenureFlag pretenure) {
-  const int kMinCapacity = 32;
-  int capacity = RoundUpToPowerOf2(at_least_space_for * 2);
-  if (capacity < kMinCapacity) {
-    capacity = kMinCapacity;  // Guarantee min capacity.
-  } else if (capacity > HashTable::kMaxCapacity) {
+  int capacity = ComputeCapacity(at_least_space_for);
+  if (capacity > HashTable::kMaxCapacity) {
     return Failure::OutOfMemoryException();
   }
 
@@ -10290,6 +9967,8 @@
 
 template class HashTable<MapCacheShape, HashTableKey*>;
 
+template class HashTable<ObjectHashTableShape, JSObject*>;
+
 template class Dictionary<StringDictionaryShape, String*>;
 
 template class Dictionary<NumberDictionaryShape, uint32_t>;
@@ -10504,19 +10183,19 @@
   } else if (HasExternalArrayElements()) {
     // External arrays cannot have holes or undefined elements.
     return Smi::FromInt(ExternalArray::cast(elements())->length());
-  } else {
+  } else if (!HasFastDoubleElements()) {
     Object* obj;
     { MaybeObject* maybe_obj = EnsureWritableFastElements();
       if (!maybe_obj->ToObject(&obj)) return maybe_obj;
     }
   }
-  ASSERT(HasFastElements());
+  ASSERT(HasFastElements() || HasFastDoubleElements());
 
   // Collect holes at the end, undefined before that and the rest at the
   // start, and return the number of non-hole, non-undefined values.
 
-  FixedArray* elements = FixedArray::cast(this->elements());
-  uint32_t elements_length = static_cast<uint32_t>(elements->length());
+  FixedArrayBase* elements_base = FixedArrayBase::cast(this->elements());
+  uint32_t elements_length = static_cast<uint32_t>(elements_base->length());
   if (limit > elements_length) {
     limit = elements_length ;
   }
@@ -10535,47 +10214,78 @@
     result_double = HeapNumber::cast(new_double);
   }
 
-  AssertNoAllocation no_alloc;
-
-  // Split elements into defined, undefined and the_hole, in that order.
-  // Only count locations for undefined and the hole, and fill them afterwards.
-  WriteBarrierMode write_barrier = elements->GetWriteBarrierMode(no_alloc);
-  unsigned int undefs = limit;
-  unsigned int holes = limit;
-  // Assume most arrays contain no holes and undefined values, so minimize the
-  // number of stores of non-undefined, non-the-hole values.
-  for (unsigned int i = 0; i < undefs; i++) {
-    Object* current = elements->get(i);
-    if (current->IsTheHole()) {
-      holes--;
-      undefs--;
-    } else if (current->IsUndefined()) {
-      undefs--;
-    } else {
-      continue;
+  uint32_t result = 0;
+  if (elements_base->map() == heap->fixed_double_array_map()) {
+    FixedDoubleArray* elements = FixedDoubleArray::cast(elements_base);
+    // Split elements into defined and the_hole, in that order.
+    unsigned int holes = limit;
+    // Assume most arrays contain no holes and undefined values, so minimize the
+    // number of stores of non-undefined, non-the-hole values.
+    for (unsigned int i = 0; i < holes; i++) {
+      if (elements->is_the_hole(i)) {
+        holes--;
+      } else {
+        continue;
+      }
+      // Position i needs to be filled.
+      while (holes > i) {
+        if (elements->is_the_hole(holes)) {
+          holes--;
+        } else {
+          elements->set(i, elements->get_scalar(holes));
+          break;
+        }
+      }
     }
-    // Position i needs to be filled.
-    while (undefs > i) {
-      current = elements->get(undefs);
+    result = holes;
+    while (holes < limit) {
+      elements->set_the_hole(holes);
+      holes++;
+    }
+  } else {
+    FixedArray* elements = FixedArray::cast(elements_base);
+    AssertNoAllocation no_alloc;
+
+    // Split elements into defined, undefined and the_hole, in that order.  Only
+    // count locations for undefined and the hole, and fill them afterwards.
+    WriteBarrierMode write_barrier = elements->GetWriteBarrierMode(no_alloc);
+    unsigned int undefs = limit;
+    unsigned int holes = limit;
+    // Assume most arrays contain no holes and undefined values, so minimize the
+    // number of stores of non-undefined, non-the-hole values.
+    for (unsigned int i = 0; i < undefs; i++) {
+      Object* current = elements->get(i);
       if (current->IsTheHole()) {
         holes--;
         undefs--;
       } else if (current->IsUndefined()) {
         undefs--;
       } else {
-        elements->set(i, current, write_barrier);
-        break;
+        continue;
+      }
+      // Position i needs to be filled.
+      while (undefs > i) {
+        current = elements->get(undefs);
+        if (current->IsTheHole()) {
+          holes--;
+          undefs--;
+        } else if (current->IsUndefined()) {
+          undefs--;
+        } else {
+          elements->set(i, current, write_barrier);
+          break;
+        }
       }
     }
-  }
-  uint32_t result = undefs;
-  while (undefs < holes) {
-    elements->set_undefined(undefs);
-    undefs++;
-  }
-  while (holes < limit) {
-    elements->set_the_hole(holes);
-    holes++;
+    result = undefs;
+    while (undefs < holes) {
+      elements->set_undefined(undefs);
+      undefs++;
+    }
+    while (holes < limit) {
+      elements->set_the_hole(holes);
+      holes++;
+    }
   }
 
   if (result <= static_cast<uint32_t>(Smi::kMaxValue)) {
@@ -11603,6 +11313,63 @@
 }
 
 
+Object* ObjectHashTable::Lookup(JSObject* key) {
+  // If the object does not have an identity hash, it was never used as a key.
+  MaybeObject* maybe_hash = key->GetIdentityHash(JSObject::OMIT_CREATION);
+  if (maybe_hash->IsFailure()) return GetHeap()->undefined_value();
+  int entry = FindEntry(key);
+  if (entry == kNotFound) return GetHeap()->undefined_value();
+  return get(EntryToIndex(entry) + 1);
+}
+
+
+MaybeObject* ObjectHashTable::Put(JSObject* key, Object* value) {
+  // Make sure the key object has an identity hash code.
+  int hash;
+  { MaybeObject* maybe_hash = key->GetIdentityHash(JSObject::ALLOW_CREATION);
+    if (maybe_hash->IsFailure()) return maybe_hash;
+    hash = Smi::cast(maybe_hash->ToObjectUnchecked())->value();
+  }
+  int entry = FindEntry(key);
+
+  // Check whether to perform removal operation.
+  if (value->IsUndefined()) {
+    if (entry == kNotFound) return this;
+    RemoveEntry(entry);
+    return Shrink(key);
+  }
+
+  // Key is already in table, just overwrite value.
+  if (entry != kNotFound) {
+    set(EntryToIndex(entry) + 1, value);
+    return this;
+  }
+
+  // Check whether the hash table should be extended.
+  Object* obj;
+  { MaybeObject* maybe_obj = EnsureCapacity(1, key);
+    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  }
+  ObjectHashTable* table = ObjectHashTable::cast(obj);
+  table->AddEntry(table->FindInsertionEntry(hash), key, value);
+  return table;
+}
+
+
+void ObjectHashTable::AddEntry(int entry, JSObject* key, Object* value) {
+  set(EntryToIndex(entry), key);
+  set(EntryToIndex(entry) + 1, value);
+  ElementAdded();
+}
+
+
+void ObjectHashTable::RemoveEntry(int entry, Heap* heap) {
+  set_null(heap, EntryToIndex(entry));
+  set_null(heap, EntryToIndex(entry) + 1);
+  ElementRemoved();
+}
+
+
 #ifdef ENABLE_DEBUGGER_SUPPORT
 // Check if there is a break point at this code position.
 bool DebugInfo::HasBreakPoint(int code_position) {
@@ -11829,7 +11596,7 @@
     Handle<Object> break_point_object) {
   // No break point.
   if (break_point_info->break_point_objects()->IsUndefined()) return false;
-  // Single beak point.
+  // Single break point.
   if (!break_point_info->break_point_objects()->IsFixedArray()) {
     return break_point_info->break_point_objects() == *break_point_object;
   }
@@ -11848,7 +11615,7 @@
 int BreakPointInfo::GetBreakPointCount() {
   // No break point.
   if (break_point_objects()->IsUndefined()) return 0;
-  // Single beak point.
+  // Single break point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
diff --git a/src/objects.h b/src/objects.h
index 2aa6b4a..53ba981 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -51,6 +51,7 @@
 //       - JSReceiver  (suitable for property access)
 //         - JSObject
 //           - JSArray
+//           - JSWeakMap
 //           - JSRegExp
 //           - JSFunction
 //           - GlobalObject
@@ -61,31 +62,34 @@
 //           - JSMessageObject
 //         - JSProxy
 //           - JSFunctionProxy
-//       - ByteArray
-//       - ExternalArray
-//         - ExternalPixelArray
-//         - ExternalByteArray
-//         - ExternalUnsignedByteArray
-//         - ExternalShortArray
-//         - ExternalUnsignedShortArray
-//         - ExternalIntArray
-//         - ExternalUnsignedIntArray
-//         - ExternalFloatArray
-//       - FixedArray
-//         - DescriptorArray
-//         - HashTable
-//           - Dictionary
-//           - SymbolTable
-//           - CompilationCacheTable
-//           - CodeCacheHashTable
-//           - MapCache
-//         - Context
-//         - JSFunctionResultCache
-//         - SerializedScopeInfo
+//       - FixedArrayBase
+//         - ByteArray
+//         - FixedArray
+//           - DescriptorArray
+//           - HashTable
+//             - Dictionary
+//             - SymbolTable
+//             - CompilationCacheTable
+//             - CodeCacheHashTable
+//             - MapCache
+//           - Context
+//           - JSFunctionResultCache
+//           - SerializedScopeInfo
+//         - FixedDoubleArray
+//         - ExternalArray
+//           - ExternalPixelArray
+//           - ExternalByteArray
+//           - ExternalUnsignedByteArray
+//           - ExternalShortArray
+//           - ExternalUnsignedShortArray
+//           - ExternalIntArray
+//           - ExternalUnsignedIntArray
+//           - ExternalFloatArray
 //       - String
 //         - SeqString
 //           - SeqAsciiString
 //           - SeqTwoByteString
+//         - SlicedString
 //         - ConsString
 //         - ExternalString
 //           - ExternalAsciiString
@@ -280,6 +284,7 @@
   V(ASCII_STRING_TYPE)                                                         \
   V(CONS_STRING_TYPE)                                                          \
   V(CONS_ASCII_STRING_TYPE)                                                    \
+  V(SLICED_STRING_TYPE)                                                        \
   V(EXTERNAL_STRING_TYPE)                                                      \
   V(EXTERNAL_STRING_WITH_ASCII_DATA_TYPE)                                      \
   V(EXTERNAL_ASCII_STRING_TYPE)                                                \
@@ -319,6 +324,7 @@
   V(POLYMORPHIC_CODE_CACHE_TYPE)                                               \
                                                                                \
   V(FIXED_ARRAY_TYPE)                                                          \
+  V(FIXED_DOUBLE_ARRAY_TYPE)                                                   \
   V(SHARED_FUNCTION_INFO_TYPE)                                                 \
                                                                                \
   V(JS_MESSAGE_OBJECT_TYPE)                                                    \
@@ -331,6 +337,7 @@
   V(JS_GLOBAL_PROXY_TYPE)                                                      \
   V(JS_ARRAY_TYPE)                                                             \
   V(JS_PROXY_TYPE)                                                             \
+  V(JS_WEAK_MAP_TYPE)                                                          \
   V(JS_REGEXP_TYPE)                                                            \
                                                                                \
   V(JS_FUNCTION_TYPE)                                                          \
@@ -396,6 +403,14 @@
     ConsString::kSize,                                                         \
     cons_ascii_string,                                                         \
     ConsAsciiString)                                                           \
+  V(SLICED_STRING_TYPE,                                                        \
+    SlicedString::kSize,                                                       \
+    sliced_string,                                                             \
+    SlicedString)                                                              \
+  V(SLICED_ASCII_STRING_TYPE,                                                  \
+    SlicedString::kSize,                                                       \
+    sliced_ascii_string,                                                       \
+    SlicedAsciiString)                                                         \
   V(EXTERNAL_STRING_TYPE,                                                      \
     ExternalTwoByteString::kSize,                                              \
     external_string,                                                           \
@@ -469,9 +484,22 @@
 enum StringRepresentationTag {
   kSeqStringTag = 0x0,
   kConsStringTag = 0x1,
-  kExternalStringTag = 0x2
+  kExternalStringTag = 0x2,
+  kSlicedStringTag = 0x3
 };
-const uint32_t kIsConsStringMask = 0x1;
+const uint32_t kIsIndirectStringMask = 0x1;
+const uint32_t kIsIndirectStringTag = 0x1;
+STATIC_ASSERT((kSeqStringTag & kIsIndirectStringMask) == 0);
+STATIC_ASSERT((kExternalStringTag & kIsIndirectStringMask) == 0);
+STATIC_ASSERT(
+    (kConsStringTag & kIsIndirectStringMask) == kIsIndirectStringTag);
+STATIC_ASSERT(
+    (kSlicedStringTag & kIsIndirectStringMask) == kIsIndirectStringTag);
+
+// Use this mask to distinguish between cons and slice only after making
+// sure that the string is one of the two (an indirect string).
+const uint32_t kSlicedNotConsMask = kSlicedStringTag & ~kConsStringTag;
+STATIC_ASSERT(IS_POWER_OF_TWO(kSlicedNotConsMask) && kSlicedNotConsMask != 0);
 
 // If bit 7 is clear, then bit 3 indicates whether this two-byte
 // string actually contains ascii data.
@@ -506,6 +534,8 @@
   ASCII_STRING_TYPE = kAsciiStringTag | kSeqStringTag,
   CONS_STRING_TYPE = kTwoByteStringTag | kConsStringTag,
   CONS_ASCII_STRING_TYPE = kAsciiStringTag | kConsStringTag,
+  SLICED_STRING_TYPE = kTwoByteStringTag | kSlicedStringTag,
+  SLICED_ASCII_STRING_TYPE = kAsciiStringTag | kSlicedStringTag,
   EXTERNAL_STRING_TYPE = kTwoByteStringTag | kExternalStringTag,
   EXTERNAL_STRING_WITH_ASCII_DATA_TYPE =
       kTwoByteStringTag | kExternalStringTag | kAsciiDataHintTag,
@@ -568,6 +598,7 @@
   JS_GLOBAL_PROXY_TYPE,
   JS_ARRAY_TYPE,
   JS_PROXY_TYPE,
+  JS_WEAK_MAP_TYPE,
 
   JS_REGEXP_TYPE,  // LAST_NONCALLABLE_SPEC_OBJECT_TYPE
 
@@ -630,8 +661,11 @@
                          WriteBarrierMode mode = UPDATE_WRITE_BARRIER); \
 
 
-class StringStream;
+class DictionaryElementsAccessor;
+class ElementsAccessor;
+class FixedArrayBase;
 class ObjectVisitor;
+class StringStream;
 
 struct ValueInfo : public Malloced {
   ValueInfo() : type(FIRST_TYPE), ptr(NULL), str(NULL), number(0) { }
@@ -709,6 +743,7 @@
   V(SeqString)                                 \
   V(ExternalString)                            \
   V(ConsString)                                \
+  V(SlicedString)                              \
   V(ExternalTwoByteString)                     \
   V(ExternalAsciiString)                       \
   V(SeqTwoByteString)                          \
@@ -736,6 +771,7 @@
   V(FixedDoubleArray)                          \
   V(Context)                                   \
   V(GlobalContext)                             \
+  V(SerializedScopeInfo)                       \
   V(JSFunction)                                \
   V(Code)                                      \
   V(Oddball)                                   \
@@ -748,6 +784,7 @@
   V(JSArray)                                   \
   V(JSProxy)                                   \
   V(JSFunctionProxy)                           \
+  V(JSWeakMap)                                 \
   V(JSRegExp)                                  \
   V(HashTable)                                 \
   V(Dictionary)                                \
@@ -790,6 +827,8 @@
   STRUCT_LIST(DECLARE_STRUCT_PREDICATE)
 #undef DECLARE_STRUCT_PREDICATE
 
+  INLINE(bool IsSpecObject());
+
   // Oddball testing.
   INLINE(bool IsUndefined());
   INLINE(bool IsNull());
@@ -1482,10 +1521,11 @@
   // In the slow mode the elements is either a NumberDictionary, an
   // ExternalArray, or a FixedArray parameter map for a (non-strict)
   // arguments object.
-  DECL_ACCESSORS(elements, HeapObject)
+  DECL_ACCESSORS(elements, FixedArrayBase)
   inline void initialize_elements();
   MUST_USE_RESULT inline MaybeObject* ResetElements();
   inline ElementsKind GetElementsKind();
+  inline ElementsAccessor* GetElementsAccessor();
   inline bool HasFastElements();
   inline bool HasFastDoubleElements();
   inline bool HasDictionaryElements();
@@ -1636,6 +1676,23 @@
   MUST_USE_RESULT inline MaybeObject* SetHiddenPropertiesObject(
       Object* hidden_obj);
 
+  // Indicates whether the hidden properties object should be created.
+  enum HiddenPropertiesFlag { ALLOW_CREATION, OMIT_CREATION };
+
+  // Retrieves the hidden properties object.
+  //
+  // The undefined value might be returned in case no hidden properties object
+  // is present and creation was omitted.
+  inline bool HasHiddenProperties();
+  MUST_USE_RESULT MaybeObject* GetHiddenProperties(HiddenPropertiesFlag flag);
+
+  // Retrieves a permanent object identity hash code.
+  //
+  // The identity hash is stored as a hidden property. The undefined value might
+  // be returned in case no hidden properties object is present and creation was
+  // omitted.
+  MUST_USE_RESULT MaybeObject* GetIdentityHash(HiddenPropertiesFlag flag);
+
   MUST_USE_RESULT MaybeObject* DeleteProperty(String* name, DeleteMode mode);
   MUST_USE_RESULT MaybeObject* DeleteElement(uint32_t index, DeleteMode mode);
 
@@ -1652,7 +1709,7 @@
   bool ShouldConvertToFastElements();
   // Returns true if the elements of JSObject contains only values that can be
   // represented in a FixedDoubleArray.
-  bool ShouldConvertToFastDoubleElements();
+  bool CanConvertToFastDoubleElements();
 
   // Tells whether the index'th element is present.
   inline bool HasElement(uint32_t index);
@@ -1711,14 +1768,8 @@
 
   // Returns the index'th element.
   // The undefined object if index is out of bounds.
-  MaybeObject* GetElementWithReceiver(Object* receiver, uint32_t index);
   MaybeObject* GetElementWithInterceptor(Object* receiver, uint32_t index);
 
-  // Get external element value at index if there is one and undefined
-  // otherwise. Can return a failure if allocation of a heap number
-  // failed.
-  MaybeObject* GetExternalElement(uint32_t index);
-
   // Replace the elements' backing store with fast elements of the given
   // capacity.  Update the length for JSArrays.  Returns the new backing
   // store.
@@ -1946,8 +1997,21 @@
   // Also maximal value of JSArray's length property.
   static const uint32_t kMaxElementCount = 0xffffffffu;
 
+  // Constants for heuristics controlling conversion of fast elements
+  // to slow elements.
+
+  // Maximal gap that can be introduced by adding an element beyond
+  // the current elements length.
   static const uint32_t kMaxGap = 1024;
-  static const int kMaxFastElementsLength = 5000;
+
+  // Maximal length of fast elements array that won't be checked for
+  // being dense enough on expansion.
+  static const int kMaxUncheckedFastElementsLength = 5000;
+
+  // Same as above but for old arrays. This limit is more strict. We
+  // don't want to be wasteful with long lived objects.
+  static const int kMaxUncheckedOldFastElementsLength = 500;
+
   static const int kInitialMaxFastElementArray = 100000;
   static const int kMaxFastProperties = 12;
   static const int kMaxInstanceSize = 255 * kPointerSize;
@@ -1969,6 +2033,8 @@
   };
 
  private:
+  friend class DictionaryElementsAccessor;
+
   MUST_USE_RESULT MaybeObject* GetElementWithCallback(Object* receiver,
                                                       Object* structure,
                                                       uint32_t index,
@@ -1989,14 +2055,10 @@
       StrictModeFlag strict_mode,
       bool check_prototype);
 
-  MaybeObject* GetElementPostInterceptor(Object* receiver, uint32_t index);
-
   MUST_USE_RESULT MaybeObject* DeletePropertyPostInterceptor(String* name,
                                                              DeleteMode mode);
   MUST_USE_RESULT MaybeObject* DeletePropertyWithInterceptor(String* name);
 
-  MUST_USE_RESULT MaybeObject* DeleteElementPostInterceptor(uint32_t index,
-                                                            DeleteMode mode);
   MUST_USE_RESULT MaybeObject* DeleteElementWithInterceptor(uint32_t index);
 
   MUST_USE_RESULT MaybeObject* DeleteFastElement(uint32_t index);
@@ -2013,6 +2075,9 @@
   // Returns true if most of the elements backing storage is used.
   bool HasDenseElements();
 
+  // Gets the current elements capacity and the number of used elements.
+  void GetElementsCapacityAndUsage(int* capacity, int* used);
+
   bool CanSetCallback(String* name);
   MUST_USE_RESULT MaybeObject* SetElementCallback(
       uint32_t index,
@@ -2049,6 +2114,8 @@
 };
 
 
+class FixedDoubleArray;
+
 // FixedArray describes fixed-sized arrays with element type Object*.
 class FixedArray: public FixedArrayBase {
  public:
@@ -2056,6 +2123,7 @@
   inline Object* get(int index);
   // Setter that uses write barrier.
   inline void set(int index, Object* value);
+  inline bool is_the_hole(int index);
 
   // Setter that doesn't need write barrier).
   inline void set(int index, Smi* value);
@@ -2157,7 +2225,8 @@
   inline void Initialize(NumberDictionary* from);
 
   // Setter and getter for elements.
-  inline double get(int index);
+  inline double get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, double value);
   inline void set_the_hole(int index);
 
@@ -2484,6 +2553,10 @@
       int at_least_space_for,
       PretenureFlag pretenure = NOT_TENURED);
 
+  // Computes the required capacity for a table holding the given
+  // number of elements. May be more than HashTable::kMaxCapacity.
+  static int ComputeCapacity(int at_least_space_for);
+
   // Returns the key at entry.
   Object* KeyAt(int entry) { return get(EntryToIndex(entry)); }
 
@@ -2906,6 +2979,48 @@
 };
 
 
+class ObjectHashTableShape {
+ public:
+  static inline bool IsMatch(JSObject* key, Object* other);
+  static inline uint32_t Hash(JSObject* key);
+  static inline uint32_t HashForObject(JSObject* key, Object* object);
+  MUST_USE_RESULT static inline MaybeObject* AsObject(JSObject* key);
+  static const int kPrefixSize = 0;
+  static const int kEntrySize = 2;
+};
+
+
+// ObjectHashTable maps keys that are JavaScript objects to object values by
+// using the identity hash of the key for hashing purposes.
+class ObjectHashTable: public HashTable<ObjectHashTableShape, JSObject*> {
+ public:
+  static inline ObjectHashTable* cast(Object* obj) {
+    ASSERT(obj->IsHashTable());
+    return reinterpret_cast<ObjectHashTable*>(obj);
+  }
+
+  // Looks up the value associated with the given key. The undefined value is
+  // returned in case the key is not present.
+  Object* Lookup(JSObject* key);
+
+  // Adds (or overwrites) the value associated with the given key. Mapping a
+  // key to the undefined value causes removal of the whole entry.
+  MUST_USE_RESULT MaybeObject* Put(JSObject* key, Object* value);
+
+ private:
+  friend class MarkCompactCollector;
+
+  void AddEntry(int entry, JSObject* key, Object* value);
+  void RemoveEntry(int entry, Heap* heap);
+  inline void RemoveEntry(int entry);
+
+  // Returns the index to the value of an entry.
+  static inline int EntryToValueIndex(int entry) {
+    return EntryToIndex(entry) + 1;
+  }
+};
+
+
 // JSFunctionResultCache caches results of some JSFunction invocation.
 // It is a fixed array with fixed structure:
 //   [0]: factory function
@@ -2968,12 +3083,8 @@
 // ByteArray represents fixed sized byte arrays.  Used by the outside world,
 // such as PCRE, and also by the memory allocator and garbage collector to
 // fill in free blocks in the heap.
-class ByteArray: public HeapObject {
+class ByteArray: public FixedArrayBase {
  public:
-  // [length]: length of the array.
-  inline int length();
-  inline void set_length(int value);
-
   // Setter and getter.
   inline byte get(int index);
   inline void set(int index, byte value);
@@ -3018,10 +3129,6 @@
 #endif
 
   // Layout description.
-  // Length is smi tagged when it is stored.
-  static const int kLengthOffset = HeapObject::kHeaderSize;
-  static const int kHeaderSize = kLengthOffset + kPointerSize;
-
   static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
 
   // Maximal memory consumption for a single ByteArray.
@@ -3045,11 +3152,10 @@
 // Out-of-range values passed to the setter are converted via a C
 // cast, not clamping. Out-of-range indices cause exceptions to be
 // raised rather than being silently ignored.
-class ExternalArray: public HeapObject {
+class ExternalArray: public FixedArrayBase {
  public:
-  // [length]: length of the array.
-  inline int length();
-  inline void set_length(int value);
+
+  inline bool is_the_hole(int index) { return false; }
 
   // [external_pointer]: The pointer to the external memory area backing this
   // external array.
@@ -3062,9 +3168,8 @@
   static const int kMaxLength = 0x3fffffff;
 
   // ExternalArray headers are not quadword aligned.
-  static const int kLengthOffset = HeapObject::kHeaderSize;
   static const int kExternalPointerOffset =
-      POINTER_SIZE_ALIGN(kLengthOffset + kIntSize);
+      POINTER_SIZE_ALIGN(FixedArrayBase::kLengthOffset + kPointerSize);
   static const int kHeaderSize = kExternalPointerOffset + kPointerSize;
   static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
 
@@ -3086,7 +3191,8 @@
   inline uint8_t* external_pixel_pointer();
 
   // Setter and getter.
-  inline uint8_t get(int index);
+  inline uint8_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, uint8_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber and
@@ -3114,7 +3220,8 @@
 class ExternalByteArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline int8_t get(int index);
+  inline int8_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, int8_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3142,7 +3249,8 @@
 class ExternalUnsignedByteArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline uint8_t get(int index);
+  inline uint8_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, uint8_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3170,7 +3278,8 @@
 class ExternalShortArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline int16_t get(int index);
+  inline int16_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, int16_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3198,7 +3307,8 @@
 class ExternalUnsignedShortArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline uint16_t get(int index);
+  inline uint16_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, uint16_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3226,7 +3336,8 @@
 class ExternalIntArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline int32_t get(int index);
+  inline int32_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, int32_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3254,7 +3365,8 @@
 class ExternalUnsignedIntArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline uint32_t get(int index);
+  inline uint32_t get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, uint32_t value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3282,7 +3394,8 @@
 class ExternalFloatArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline float get(int index);
+  inline float get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, float value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3310,7 +3423,8 @@
 class ExternalDoubleArray: public ExternalArray {
  public:
   // Setter and getter.
-  inline double get(int index);
+  inline double get_scalar(int index);
+  inline MaybeObject* get(int index);
   inline void set(int index, double value);
 
   // This accessor applies the correct conversion from Smi, HeapNumber
@@ -3480,13 +3594,14 @@
     UNARY_OP_IC,
     BINARY_OP_IC,
     COMPARE_IC,
+    TO_BOOLEAN_IC,
     // No more than 16 kinds. The value currently encoded in four bits in
     // Flags.
 
     // Pseudo-kinds.
     REGEXP = BUILTIN,
     FIRST_IC_KIND = LOAD_IC,
-    LAST_IC_KIND = COMPARE_IC
+    LAST_IC_KIND = TO_BOOLEAN_IC
   };
 
   enum {
@@ -3552,13 +3667,10 @@
   inline bool is_keyed_store_stub() { return kind() == KEYED_STORE_IC; }
   inline bool is_call_stub() { return kind() == CALL_IC; }
   inline bool is_keyed_call_stub() { return kind() == KEYED_CALL_IC; }
-  inline bool is_unary_op_stub() {
-    return kind() == UNARY_OP_IC;
-  }
-  inline bool is_binary_op_stub() {
-    return kind() == BINARY_OP_IC;
-  }
+  inline bool is_unary_op_stub() { return kind() == UNARY_OP_IC; }
+  inline bool is_binary_op_stub() { return kind() == BINARY_OP_IC; }
   inline bool is_compare_ic_stub() { return kind() == COMPARE_IC; }
+  inline bool is_to_boolean_ic_stub() { return kind() == TO_BOOLEAN_IC; }
 
   // [major_key]: For kind STUB or BINARY_OP_IC, the major key.
   inline int major_key();
@@ -3600,21 +3712,24 @@
   inline CheckType check_type();
   inline void set_check_type(CheckType value);
 
-  // [type-recording unary op type]: For all UNARY_OP_IC.
+  // [type-recording unary op type]: For kind UNARY_OP_IC.
   inline byte unary_op_type();
   inline void set_unary_op_type(byte value);
 
-  // [type-recording binary op type]: For all TYPE_RECORDING_BINARY_OP_IC.
+  // [type-recording binary op type]: For kind BINARY_OP_IC.
   inline byte binary_op_type();
   inline void set_binary_op_type(byte value);
   inline byte binary_op_result_type();
   inline void set_binary_op_result_type(byte value);
 
-  // [compare state]: For kind compare IC stubs, tells what state the
-  // stub is in.
+  // [compare state]: For kind COMPARE_IC, tells what state the stub is in.
   inline byte compare_state();
   inline void set_compare_state(byte value);
 
+  // [to_boolean_foo]: For kind TO_BOOLEAN_IC tells what state the stub is in.
+  inline byte to_boolean_state();
+  inline void set_to_boolean_state(byte value);
+
   // Get the safepoint entry for the given pc.
   SafepointEntry GetSafepointEntry(Address pc);
 
@@ -3756,9 +3871,10 @@
   static const int kStackSlotsOffset = kKindSpecificFlagsOffset;
   static const int kCheckTypeOffset = kKindSpecificFlagsOffset;
 
-  static const int kCompareStateOffset = kStubMajorKeyOffset + 1;
   static const int kUnaryOpTypeOffset = kStubMajorKeyOffset + 1;
   static const int kBinaryOpTypeOffset = kStubMajorKeyOffset + 1;
+  static const int kCompareStateOffset = kStubMajorKeyOffset + 1;
+  static const int kToBooleanTypeOffset = kStubMajorKeyOffset + 1;
   static const int kHasDeoptimizationSupportOffset = kOptimizableOffset + 1;
 
   static const int kBinaryOpReturnTypeOffset = kBinaryOpTypeOffset + 1;
@@ -5693,12 +5809,15 @@
   inline bool IsSequential();
   inline bool IsExternal();
   inline bool IsCons();
+  inline bool IsSliced();
+  inline bool IsIndirect();
   inline bool IsExternalAscii();
   inline bool IsExternalTwoByte();
   inline bool IsSequentialAscii();
   inline bool IsSequentialTwoByte();
   inline bool IsSymbol();
   inline StringRepresentationTag representation_tag();
+  inline uint32_t encoding_tag();
   inline uint32_t full_representation_tag();
   inline uint32_t size_tag();
 #ifdef DEBUG
@@ -5730,6 +5849,51 @@
 // All string values have a length field.
 class String: public HeapObject {
  public:
+  // Representation of the flat content of a String.
+  // A non-flat string doesn't have flat content.
+  // A flat string has content that's encoded as a sequence of either
+  // ASCII chars or two-byte UC16.
+  // Returned by String::GetFlatContent().
+  class FlatContent {
+   public:
+    // Returns true if the string is flat and this structure contains content.
+    bool IsFlat() { return state_ != NON_FLAT; }
+    // Returns true if the structure contains ASCII content.
+    bool IsAscii() { return state_ == ASCII; }
+    // Returns true if the structure contains two-byte content.
+    bool IsTwoByte() { return state_ == TWO_BYTE; }
+
+    // Return the ASCII content of the string. Only use if IsAscii() returns
+    // true.
+    Vector<const char> ToAsciiVector() {
+      ASSERT_EQ(ASCII, state_);
+      return Vector<const char>::cast(buffer_);
+    }
+    // Return the two-byte content of the string. Only use if IsTwoByte()
+    // returns true.
+    Vector<const uc16> ToUC16Vector() {
+      ASSERT_EQ(TWO_BYTE, state_);
+      return Vector<const uc16>::cast(buffer_);
+    }
+
+   private:
+    enum State { NON_FLAT, ASCII, TWO_BYTE };
+
+    // Constructors only used by String::GetFlatContent().
+    explicit FlatContent(Vector<const char> chars)
+        : buffer_(Vector<const byte>::cast(chars)),
+          state_(ASCII) { }
+    explicit FlatContent(Vector<const uc16> chars)
+        : buffer_(Vector<const byte>::cast(chars)),
+          state_(TWO_BYTE) { }
+    FlatContent() : buffer_(), state_(NON_FLAT) { }
+
+    Vector<const byte> buffer_;
+    State state_;
+
+    friend class String;
+  };
+
   // Get and set the length of the string.
   inline int length();
   inline void set_length(int value);
@@ -5738,14 +5902,19 @@
   inline uint32_t hash_field();
   inline void set_hash_field(uint32_t value);
 
+  // Returns whether this string has only ASCII chars, i.e. all of them can
+  // be ASCII encoded.  This might be the case even if the string is
+  // two-byte.  Such strings may appear when the embedder prefers
+  // two-byte external representations even for ASCII data.
   inline bool IsAsciiRepresentation();
   inline bool IsTwoByteRepresentation();
 
-  // Returns whether this string has ascii chars, i.e. all of them can
-  // be ascii encoded.  This might be the case even if the string is
-  // two-byte.  Such strings may appear when the embedder prefers
-  // two-byte external representations even for ascii data.
-  //
+  // Cons and slices have an encoding flag that may not represent the actual
+  // encoding of the underlying string.  This is taken into account here.
+  // Requires: this->IsFlat()
+  inline bool IsAsciiRepresentationUnderneath();
+  inline bool IsTwoByteRepresentationUnderneath();
+
   // NOTE: this should be considered only a hint.  False negatives are
   // possible.
   inline bool HasOnlyAsciiChars();
@@ -5778,8 +5947,16 @@
   // string.
   inline String* TryFlattenGetString(PretenureFlag pretenure = NOT_TENURED);
 
-  Vector<const char> ToAsciiVector();
-  Vector<const uc16> ToUC16Vector();
+  // Tries to return the content of a flat string as a structure holding either
+  // a flat vector of char or of uc16.
+  // If the string isn't flat, and therefore doesn't have flat content, the
+  // returned structure will report so, and can't provide a vector of either
+  // kind.
+  FlatContent GetFlatContent();
+
+  // Returns the parent of a sliced string or first part of a flat cons string.
+  // Requires: StringShape(this).IsIndirect() && this->IsFlat()
+  inline String* GetUnderlying();
 
   // Mark the string as an undetectable object. It only applies to
   // ascii and two byte string types.
@@ -5860,6 +6037,8 @@
     StringPrint(stdout);
   }
   void StringPrint(FILE* out);
+
+  char* ToAsciiArray();
 #endif
 #ifdef DEBUG
   void StringVerify();
@@ -6207,11 +6386,69 @@
   typedef FixedBodyDescriptor<kFirstOffset, kSecondOffset + kPointerSize, kSize>
           BodyDescriptor;
 
+#ifdef DEBUG
+  void ConsStringVerify();
+#endif
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ConsString);
 };
 
 
+// The Sliced String class describes strings that are substrings of another
+// sequential string.  The motivation is to save time and memory when creating
+// a substring.  A Sliced String is described as a pointer to the parent,
+// the offset from the start of the parent string and the length.  Using
+// a Sliced String therefore requires unpacking of the parent string and
+// adding the offset to the start address.  A substring of a Sliced String
+// are not nested since the double indirection is simplified when creating
+// such a substring.
+// Currently missing features are:
+//  - handling externalized parent strings
+//  - external strings as parent
+//  - truncating sliced string to enable otherwise unneeded parent to be GC'ed.
+class SlicedString: public String {
+ public:
+
+  inline String* parent();
+  inline void set_parent(String* parent);
+  inline int offset();
+  inline void set_offset(int offset);
+
+  // Dispatched behavior.
+  uint16_t SlicedStringGet(int index);
+
+  // Casting.
+  static inline SlicedString* cast(Object* obj);
+
+  // Layout description.
+  static const int kParentOffset = POINTER_SIZE_ALIGN(String::kSize);
+  static const int kOffsetOffset = kParentOffset + kPointerSize;
+  static const int kSize = kOffsetOffset + kPointerSize;
+
+  // Support for StringInputBuffer
+  inline const unibrow::byte* SlicedStringReadBlock(ReadBlockBuffer* buffer,
+                                                    unsigned* offset_ptr,
+                                                    unsigned chars);
+  inline void SlicedStringReadBlockIntoBuffer(ReadBlockBuffer* buffer,
+                                              unsigned* offset_ptr,
+                                              unsigned chars);
+  // Minimum length for a sliced string.
+  static const int kMinLength = 13;
+
+  typedef FixedBodyDescriptor<kParentOffset,
+                              kOffsetOffset + kPointerSize, kSize>
+          BodyDescriptor;
+
+#ifdef DEBUG
+  void SlicedStringVerify();
+#endif
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(SlicedString);
+};
+
+
 // The ExternalString class describes string values that are backed by
 // a string resource that lies outside the V8 heap.  ExternalStrings
 // consist of the length field common to all strings, a pointer to the
@@ -6551,6 +6788,40 @@
 };
 
 
+// The JSWeakMap describes EcmaScript Harmony weak maps
+class JSWeakMap: public JSObject {
+ public:
+  // [table]: the backing hash table mapping keys to values.
+  DECL_ACCESSORS(table, ObjectHashTable)
+
+  // [next]: linked list of encountered weak maps during GC.
+  DECL_ACCESSORS(next, Object)
+
+  // Unchecked accessors to be used during GC.
+  inline ObjectHashTable* unchecked_table();
+
+  // Casting.
+  static inline JSWeakMap* cast(Object* obj);
+
+#ifdef OBJECT_PRINT
+  inline void JSWeakMapPrint() {
+    JSWeakMapPrint(stdout);
+  }
+  void JSWeakMapPrint(FILE* out);
+#endif
+#ifdef DEBUG
+  void JSWeakMapVerify();
+#endif
+
+  static const int kTableOffset = JSObject::kHeaderSize;
+  static const int kNextOffset = kTableOffset + kPointerSize;
+  static const int kSize = kNextOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakMap);
+};
+
+
 // Foreign describes objects pointing from JavaScript to C structures.
 // Since they cannot contain references to JS HeapObjects they can be
 // placed in old_data_space.
@@ -6850,7 +7121,6 @@
   DECL_ACCESSORS(instance_call_handler, Object)
   DECL_ACCESSORS(access_check_info, Object)
   DECL_ACCESSORS(flag, Smi)
-  DECL_ACCESSORS(prototype_attributes, Smi)
 
   // Following properties use flag bits.
   DECL_BOOLEAN_ACCESSORS(hidden_prototype)
@@ -6858,6 +7128,7 @@
   // If the bit is set, object instances created by this function
   // requires access check.
   DECL_BOOLEAN_ACCESSORS(needs_access_check)
+  DECL_BOOLEAN_ACCESSORS(read_only_prototype)
 
   static inline FunctionTemplateInfo* cast(Object* obj);
 
@@ -6890,14 +7161,14 @@
   static const int kAccessCheckInfoOffset =
       kInstanceCallHandlerOffset + kPointerSize;
   static const int kFlagOffset = kAccessCheckInfoOffset + kPointerSize;
-  static const int kPrototypeAttributesOffset = kFlagOffset + kPointerSize;
-  static const int kSize = kPrototypeAttributesOffset + kPointerSize;
+  static const int kSize = kFlagOffset + kPointerSize;
 
  private:
   // Bit position in the flag, from least significant bit position.
   static const int kHiddenPrototypeBit   = 0;
   static const int kUndetectableBit      = 1;
   static const int kNeedsAccessCheckBit  = 2;
+  static const int kReadOnlyPrototypeBit = 3;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FunctionTemplateInfo);
 };
diff --git a/src/parser.cc b/src/parser.cc
index ece0cfe..f8c7c41 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -584,7 +584,8 @@
       pre_data_(pre_data),
       fni_(NULL),
       stack_overflow_(false),
-      parenthesized_function_(false) {
+      parenthesized_function_(false),
+      harmony_block_scoping_(false) {
   AstNode::ResetIds();
 }
 
@@ -809,6 +810,10 @@
   isolate()->Throw(*result, &location);
 }
 
+void Parser::SetHarmonyBlockScoping(bool block_scoping) {
+  scanner().SetHarmonyBlockScoping(block_scoping);
+  harmony_block_scoping_ = block_scoping;
+}
 
 // Base class containing common code for the different finder classes used by
 // the parser.
@@ -1106,6 +1111,25 @@
 };
 
 
+Statement* Parser::ParseSourceElement(ZoneStringList* labels,
+                                      bool* ok) {
+  if (peek() == Token::FUNCTION) {
+    // FunctionDeclaration is only allowed in the context of SourceElements
+    // (Ecma 262 5th Edition, clause 14):
+    // SourceElement:
+    //    Statement
+    //    FunctionDeclaration
+    // Common language extension is to allow function declaration in place
+    // of any statement. This language extension is disabled in strict mode.
+    return ParseFunctionDeclaration(ok);
+  } else if (peek() == Token::LET) {
+    return ParseVariableStatement(kSourceElement, ok);
+  } else {
+    return ParseStatement(labels, ok);
+  }
+}
+
+
 void* Parser::ParseSourceElements(ZoneList<Statement*>* processor,
                                   int end_token,
                                   bool* ok) {
@@ -1129,21 +1153,7 @@
     }
 
     Scanner::Location token_loc = scanner().peek_location();
-
-    Statement* stat;
-    if (peek() == Token::FUNCTION) {
-      // FunctionDeclaration is only allowed in the context of SourceElements
-      // (Ecma 262 5th Edition, clause 14):
-      // SourceElement:
-      //    Statement
-      //    FunctionDeclaration
-      // Common language extension is to allow function declaration in place
-      // of any statement. This language extension is disabled in strict mode.
-      stat = ParseFunctionDeclaration(CHECK_OK);
-    } else {
-      stat = ParseStatement(NULL, CHECK_OK);
-    }
-
+    Statement* stat = ParseSourceElement(NULL, CHECK_OK);
     if (stat == NULL || stat->IsEmpty()) {
       directive_prologue = false;   // End of directive prologue.
       continue;
@@ -1231,7 +1241,7 @@
 
     case Token::CONST:  // fall through
     case Token::VAR:
-      stmt = ParseVariableStatement(ok);
+      stmt = ParseVariableStatement(kStatement, ok);
       break;
 
     case Token::SEMICOLON:
@@ -1326,9 +1336,9 @@
                                bool resolve,
                                bool* ok) {
   Variable* var = NULL;
-  // If we are inside a function, a declaration of a variable
-  // is a truly local variable, and the scope of the variable
-  // is always the function scope.
+  // If we are inside a function, a declaration of a var/const variable is a
+  // truly local variable, and the scope of the variable is always the function
+  // scope.
 
   // If a function scope exists, then we can statically declare this
   // variable and also set its mode. In any case, a Declaration node
@@ -1338,24 +1348,28 @@
   // to the calling function context.
   // Similarly, strict mode eval scope does not leak variable declarations to
   // the caller's scope so we declare all locals, too.
-  Scope* declaration_scope = top_scope_->DeclarationScope();
+
+  Scope* declaration_scope = mode == Variable::LET ? top_scope_
+      : top_scope_->DeclarationScope();
   if (declaration_scope->is_function_scope() ||
-      declaration_scope->is_strict_mode_eval_scope()) {
+      declaration_scope->is_strict_mode_eval_scope() ||
+      declaration_scope->is_block_scope()) {
     // Declare the variable in the function scope.
     var = declaration_scope->LocalLookup(name);
     if (var == NULL) {
       // Declare the name.
       var = declaration_scope->DeclareLocal(name, mode);
     } else {
-      // The name was declared before; check for conflicting
-      // re-declarations. If the previous declaration was a const or the
-      // current declaration is a const then we have a conflict. There is
-      // similar code in runtime.cc in the Declare functions.
-      if ((mode == Variable::CONST) || (var->mode() == Variable::CONST)) {
-        // We only have vars and consts in declarations.
+      // The name was declared before; check for conflicting re-declarations.
+      // We have a conflict if either of the declarations is not a var. There
+      // is similar code in runtime.cc in the Declare functions.
+      if ((mode != Variable::VAR) || (var->mode() != Variable::VAR)) {
+        // We only have vars, consts and lets in declarations.
         ASSERT(var->mode() == Variable::VAR ||
-               var->mode() == Variable::CONST);
-        const char* type = (var->mode() == Variable::VAR) ? "var" : "const";
+               var->mode() == Variable::CONST ||
+               var->mode() == Variable::LET);
+        const char* type = (var->mode() == Variable::VAR) ? "var" :
+                           (var->mode() == Variable::CONST) ? "const" : "let";
         Handle<String> type_string =
             isolate()->factory()->NewStringFromUtf8(CStrVector(type), TENURED);
         Expression* expression =
@@ -1498,12 +1512,15 @@
   // Even if we're not at the top-level of the global or a function
   // scope, we treat is as such and introduce the function with it's
   // initial value upon entering the corresponding scope.
-  Declare(name, Variable::VAR, fun, true, CHECK_OK);
+  Variable::Mode mode = harmony_block_scoping_ ? Variable::LET : Variable::VAR;
+  Declare(name, mode, fun, true, CHECK_OK);
   return EmptyStatement();
 }
 
 
 Block* Parser::ParseBlock(ZoneStringList* labels, bool* ok) {
+  if (harmony_block_scoping_) return ParseScopedBlock(labels, ok);
+
   // Block ::
   //   '{' Statement* '}'
 
@@ -1527,12 +1544,65 @@
 }
 
 
-Block* Parser::ParseVariableStatement(bool* ok) {
+Block* Parser::ParseScopedBlock(ZoneStringList* labels, bool* ok) {
+  // Construct block expecting 16 statements.
+  Block* body = new(zone()) Block(isolate(), labels, 16, false);
+  Scope* saved_scope = top_scope_;
+  Scope* block_scope = NewScope(top_scope_,
+                                Scope::BLOCK_SCOPE,
+                                inside_with());
+  body->set_block_scope(block_scope);
+  block_scope->DeclareLocal(isolate()->factory()->block_scope_symbol(),
+                            Variable::VAR);
+  if (top_scope_->is_strict_mode()) {
+    block_scope->EnableStrictMode();
+  }
+  top_scope_ = block_scope;
+
+  // Parse the statements and collect escaping labels.
+  TargetCollector collector;
+  Target target(&this->target_stack_, &collector);
+  Expect(Token::LBRACE, CHECK_OK);
+  {
+    Target target_body(&this->target_stack_, body);
+    InitializationBlockFinder block_finder(top_scope_, target_stack_);
+
+    while (peek() != Token::RBRACE) {
+      Statement* stat = ParseSourceElement(NULL, CHECK_OK);
+      if (stat && !stat->IsEmpty()) {
+        body->AddStatement(stat);
+        block_finder.Update(stat);
+      }
+    }
+  }
+  Expect(Token::RBRACE, CHECK_OK);
+
+  // Create exit block.
+  Block* exit = new(zone()) Block(isolate(), NULL, 1, false);
+  exit->AddStatement(new(zone()) ExitContextStatement());
+
+  // Create a try-finally statement.
+  TryFinallyStatement* try_finally =
+      new(zone()) TryFinallyStatement(body, exit);
+  try_finally->set_escaping_targets(collector.targets());
+  top_scope_ = saved_scope;
+
+  // Create a result block.
+  Block* result = new(zone()) Block(isolate(), NULL, 1, false);
+  result->AddStatement(try_finally);
+  return result;
+}
+
+
+Block* Parser::ParseVariableStatement(VariableDeclarationContext var_context,
+                                      bool* ok) {
   // VariableStatement ::
   //   VariableDeclarations ';'
 
   Handle<String> ignore;
-  Block* result = ParseVariableDeclarations(true, &ignore, CHECK_OK);
+  Block* result = ParseVariableDeclarations(var_context,
+                                            &ignore,
+                                            CHECK_OK);
   ExpectSemicolon(CHECK_OK);
   return result;
 }
@@ -1549,33 +1619,54 @@
 // *var is untouched; in particular, it is the caller's responsibility
 // to initialize it properly. This mechanism is used for the parsing
 // of 'for-in' loops.
-Block* Parser::ParseVariableDeclarations(bool accept_IN,
+Block* Parser::ParseVariableDeclarations(VariableDeclarationContext var_context,
                                          Handle<String>* out,
                                          bool* ok) {
   // VariableDeclarations ::
   //   ('var' | 'const') (Identifier ('=' AssignmentExpression)?)+[',']
 
   Variable::Mode mode = Variable::VAR;
+  // True if the binding needs initialization. 'let' and 'const' declared
+  // bindings are created uninitialized by their declaration nodes and
+  // need initialization. 'var' declared bindings are always initialized
+  // immediately by their declaration nodes.
+  bool needs_init = false;
   bool is_const = false;
-  Scope* declaration_scope = top_scope_->DeclarationScope();
+  Token::Value init_op = Token::INIT_VAR;
   if (peek() == Token::VAR) {
     Consume(Token::VAR);
   } else if (peek() == Token::CONST) {
     Consume(Token::CONST);
-    if (declaration_scope->is_strict_mode()) {
+    if (top_scope_->is_strict_mode()) {
       ReportMessage("strict_const", Vector<const char*>::empty());
       *ok = false;
       return NULL;
     }
     mode = Variable::CONST;
     is_const = true;
+    needs_init = true;
+    init_op = Token::INIT_CONST;
+  } else if (peek() == Token::LET) {
+    Consume(Token::LET);
+    if (var_context != kSourceElement &&
+        var_context != kForStatement) {
+      ASSERT(var_context == kStatement);
+      ReportMessage("unprotected_let", Vector<const char*>::empty());
+      *ok = false;
+      return NULL;
+    }
+    mode = Variable::LET;
+    needs_init = true;
+    init_op = Token::INIT_LET;
   } else {
     UNREACHABLE();  // by current callers
   }
 
-  // The scope of a variable/const declared anywhere inside a function
+  Scope* declaration_scope = mode == Variable::LET
+      ? top_scope_ : top_scope_->DeclarationScope();
+  // The scope of a var/const declared variable anywhere inside a function
   // is the entire function (ECMA-262, 3rd, 10.1.3, and 12.2). Thus we can
-  // transform a source-level variable/const declaration into a (Function)
+  // transform a source-level var/const declaration into a (Function)
   // Scope declaration, and rewrite the source-level initialization into an
   // assignment statement. We use a block to collect multiple assignments.
   //
@@ -1659,18 +1750,19 @@
     if (peek() == Token::ASSIGN) {
       Expect(Token::ASSIGN, CHECK_OK);
       position = scanner().location().beg_pos;
-      value = ParseAssignmentExpression(accept_IN, CHECK_OK);
+      value = ParseAssignmentExpression(var_context != kForStatement, CHECK_OK);
       // Don't infer if it is "a = function(){...}();"-like expression.
       if (fni_ != NULL &&
           value->AsCall() == NULL &&
           value->AsCallNew() == NULL) {
         fni_->Infer();
+      } else {
+        fni_->RemoveLastFunction();
       }
     }
 
-    // Make sure that 'const c' actually initializes 'c' to undefined
-    // even though it seems like a stupid thing to do.
-    if (value == NULL && is_const) {
+    // Make sure that 'const x' and 'let x' initialize 'x' to undefined.
+    if (value == NULL && needs_init) {
       value = GetLiteralUndefined();
     }
 
@@ -1758,12 +1850,11 @@
     // for constant lookups is always the function context, while it is
     // the top context for variables). Sigh...
     if (value != NULL) {
-      Token::Value op = (is_const ? Token::INIT_CONST : Token::INIT_VAR);
       bool in_with = is_const ? false : inside_with();
       VariableProxy* proxy =
           initialization_scope->NewUnresolved(name, in_with);
       Assignment* assignment =
-          new(zone()) Assignment(isolate(), op, proxy, value, position);
+          new(zone()) Assignment(isolate(), init_op, proxy, value, position);
       if (block) {
         block->AddStatement(new(zone()) ExpressionStatement(assignment));
       }
@@ -1973,41 +2064,6 @@
 }
 
 
-Block* Parser::WithHelper(Expression* obj, ZoneStringList* labels, bool* ok) {
-  // Parse the statement and collect escaping labels.
-  TargetCollector collector;
-  Statement* stat;
-  { Target target(&this->target_stack_, &collector);
-    with_nesting_level_++;
-    top_scope_->DeclarationScope()->RecordWithStatement();
-    stat = ParseStatement(labels, CHECK_OK);
-    with_nesting_level_--;
-  }
-  // Create resulting block with two statements.
-  // 1: Evaluate the with expression.
-  // 2: The try-finally block evaluating the body.
-  Block* result = new(zone()) Block(isolate(), NULL, 2, false);
-
-  if (result != NULL) {
-    result->AddStatement(new(zone()) EnterWithContextStatement(obj));
-
-    // Create body block.
-    Block* body = new(zone()) Block(isolate(), NULL, 1, false);
-    body->AddStatement(stat);
-
-    // Create exit block.
-    Block* exit = new(zone()) Block(isolate(), NULL, 1, false);
-    exit->AddStatement(new(zone()) ExitContextStatement());
-
-    // Return a try-finally statement.
-    TryFinallyStatement* wrapper = new(zone()) TryFinallyStatement(body, exit);
-    wrapper->set_escaping_targets(collector.targets());
-    result->AddStatement(wrapper);
-  }
-  return result;
-}
-
-
 Statement* Parser::ParseWithStatement(ZoneStringList* labels, bool* ok) {
   // WithStatement ::
   //   'with' '(' Expression ')' Statement
@@ -2024,7 +2080,11 @@
   Expression* expr = ParseExpression(true, CHECK_OK);
   Expect(Token::RPAREN, CHECK_OK);
 
-  return WithHelper(expr, labels, CHECK_OK);
+  ++with_nesting_level_;
+  top_scope_->DeclarationScope()->RecordWithStatement();
+  Statement* stmt = ParseStatement(labels, CHECK_OK);
+  --with_nesting_level_;
+  return new(zone()) WithStatement(expr, stmt);
 }
 
 
@@ -2159,39 +2219,22 @@
     Expect(Token::RPAREN, CHECK_OK);
 
     if (peek() == Token::LBRACE) {
-      // Rewrite the catch body B to a single statement block
-      // { try B finally { PopContext }}.
-      Block* inner_body;
-      // We need to collect escapes from the body for both the inner
-      // try/finally used to pop the catch context and any possible outer
-      // try/finally.
-      TargetCollector inner_collector;
-      { Target target(&this->target_stack_, &catch_collector);
-        { Target target(&this->target_stack_, &inner_collector);
-          catch_scope = NewScope(top_scope_, Scope::CATCH_SCOPE, inside_with());
-          if (top_scope_->is_strict_mode()) {
-            catch_scope->EnableStrictMode();
-          }
-          catch_variable = catch_scope->DeclareLocal(name, Variable::VAR);
-
-          Scope* saved_scope = top_scope_;
-          top_scope_ = catch_scope;
-          inner_body = ParseBlock(NULL, CHECK_OK);
-          top_scope_ = saved_scope;
-        }
+      // Rewrite the catch body { B } to a block:
+      // { { B } ExitContext; }.
+      Target target(&this->target_stack_, &catch_collector);
+      catch_scope = NewScope(top_scope_, Scope::CATCH_SCOPE, inside_with());
+      if (top_scope_->is_strict_mode()) {
+        catch_scope->EnableStrictMode();
       }
+      catch_variable = catch_scope->DeclareLocal(name, Variable::VAR);
+      catch_block = new(zone()) Block(isolate(), NULL, 2, false);
 
-      // Create exit block.
-      Block* inner_finally = new(zone()) Block(isolate(), NULL, 1, false);
-      inner_finally->AddStatement(new(zone()) ExitContextStatement());
-
-      // Create a try/finally statement.
-      TryFinallyStatement* inner_try_finally =
-          new(zone()) TryFinallyStatement(inner_body, inner_finally);
-      inner_try_finally->set_escaping_targets(inner_collector.targets());
-
-      catch_block = new(zone()) Block(isolate(), NULL, 1, false);
-      catch_block->AddStatement(inner_try_finally);
+      Scope* saved_scope = top_scope_;
+      top_scope_ = catch_scope;
+      Block* catch_body = ParseBlock(NULL, CHECK_OK);
+      top_scope_ = saved_scope;
+      catch_block->AddStatement(catch_body);
+      catch_block->AddStatement(new(zone()) ExitContextStatement());
     } else {
       Expect(Token::LBRACE, CHECK_OK);
     }
@@ -2307,7 +2350,7 @@
     if (peek() == Token::VAR || peek() == Token::CONST) {
       Handle<String> name;
       Block* variable_statement =
-          ParseVariableDeclarations(false, &name, CHECK_OK);
+          ParseVariableDeclarations(kForStatement, &name, CHECK_OK);
 
       if (peek() == Token::IN && !name.is_null()) {
         VariableProxy* each = top_scope_->NewUnresolved(name, inside_with());
@@ -2465,6 +2508,8 @@
          || op == Token::ASSIGN)
         && (right->AsCall() == NULL && right->AsCallNew() == NULL)) {
       fni_->Infer();
+    } else {
+      fni_->RemoveLastFunction();
     }
     fni_->Leave();
   }
@@ -2777,7 +2822,7 @@
           Handle<String> name = callee->name();
           Variable* var = top_scope_->Lookup(name);
           if (var == NULL) {
-            top_scope_->RecordEvalCall();
+            top_scope_->DeclarationScope()->RecordEvalCall();
           }
         }
         result = NewCall(result, args, pos);
@@ -3666,8 +3711,11 @@
   }
 
   int num_parameters = 0;
-  // Function declarations are hoisted.
-  Scope* scope = (type == FunctionLiteral::DECLARATION)
+  // Function declarations are function scoped in normal mode, so they are
+  // hoisted. In harmony block scoping mode they are block scoped, so they
+  // are not hoisted.
+  Scope* scope = (type == FunctionLiteral::DECLARATION &&
+                  !harmony_block_scoping_)
       ? NewScope(top_scope_->DeclarationScope(), Scope::FUNCTION_SCOPE, false)
       : NewScope(top_scope_, Scope::FUNCTION_SCOPE, inside_with());
   ZoneList<Statement*>* body = new(zone()) ZoneList<Statement*>(8);
@@ -3969,7 +4017,7 @@
 }
 
 
-// Parses and identifier that is valid for the current scope, in particular it
+// Parses an identifier that is valid for the current scope, in particular it
 // fails on strict mode future reserved keywords in a strict scope.
 Handle<String> Parser::ParseIdentifier(bool* ok) {
   if (top_scope_->is_strict_mode()) {
@@ -5050,9 +5098,11 @@
 // Create a Scanner for the preparser to use as input, and preparse the source.
 static ScriptDataImpl* DoPreParse(UC16CharacterStream* source,
                                   bool allow_lazy,
-                                  ParserRecorder* recorder) {
+                                  ParserRecorder* recorder,
+                                  bool harmony_block_scoping) {
   Isolate* isolate = Isolate::Current();
   JavaScriptScanner scanner(isolate->unicode_cache());
+  scanner.SetHarmonyBlockScoping(harmony_block_scoping);
   scanner.Initialize(source);
   intptr_t stack_limit = isolate->stack_guard()->real_climit();
   if (!preparser::PreParser::PreParseProgram(&scanner,
@@ -5073,7 +5123,8 @@
 // Preparse, but only collect data that is immediately useful,
 // even if the preparser data is only used once.
 ScriptDataImpl* ParserApi::PartialPreParse(UC16CharacterStream* source,
-                                           v8::Extension* extension) {
+                                           v8::Extension* extension,
+                                           bool harmony_block_scoping) {
   bool allow_lazy = FLAG_lazy && (extension == NULL);
   if (!allow_lazy) {
     // Partial preparsing is only about lazily compiled functions.
@@ -5081,16 +5132,17 @@
     return NULL;
   }
   PartialParserRecorder recorder;
-  return DoPreParse(source, allow_lazy, &recorder);
+  return DoPreParse(source, allow_lazy, &recorder, harmony_block_scoping);
 }
 
 
 ScriptDataImpl* ParserApi::PreParse(UC16CharacterStream* source,
-                                    v8::Extension* extension) {
+                                    v8::Extension* extension,
+                                    bool harmony_block_scoping) {
   Handle<Script> no_script;
   bool allow_lazy = FLAG_lazy && (extension == NULL);
   CompleteParserRecorder recorder;
-  return DoPreParse(source, allow_lazy, &recorder);
+  return DoPreParse(source, allow_lazy, &recorder, harmony_block_scoping);
 }
 
 
@@ -5120,18 +5172,25 @@
   ASSERT(info->function() == NULL);
   FunctionLiteral* result = NULL;
   Handle<Script> script = info->script();
+  bool harmony_block_scoping = !info->is_native() &&
+                               FLAG_harmony_block_scoping;
   if (info->is_lazy()) {
     bool allow_natives_syntax =
         FLAG_allow_natives_syntax ||
         info->is_native();
     Parser parser(script, allow_natives_syntax, NULL, NULL);
+    parser.SetHarmonyBlockScoping(harmony_block_scoping);
     result = parser.ParseLazy(info);
   } else {
     // Whether we allow %identifier(..) syntax.
     bool allow_natives_syntax =
         info->is_native() || FLAG_allow_natives_syntax;
     ScriptDataImpl* pre_data = info->pre_parse_data();
-    Parser parser(script, allow_natives_syntax, info->extension(), pre_data);
+    Parser parser(script,
+                  allow_natives_syntax,
+                  info->extension(),
+                  pre_data);
+    parser.SetHarmonyBlockScoping(harmony_block_scoping);
     if (pre_data != NULL && pre_data->has_error()) {
       Scanner::Location loc = pre_data->MessageLocation();
       const char* message = pre_data->BuildMessage();
@@ -5150,7 +5209,6 @@
                                    info->StrictMode());
     }
   }
-
   info->SetFunction(result);
   return (result != NULL);
 }
diff --git a/src/parser.h b/src/parser.h
index 535b639..686dac8 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -164,12 +164,14 @@
 
   // Generic preparser generating full preparse data.
   static ScriptDataImpl* PreParse(UC16CharacterStream* source,
-                                  v8::Extension* extension);
+                                  v8::Extension* extension,
+                                  bool harmony_block_scoping);
 
   // Preparser that only does preprocessing that makes sense if only used
   // immediately after.
   static ScriptDataImpl* PartialPreParse(UC16CharacterStream* source,
-                                         v8::Extension* extension);
+                                         v8::Extension* extension,
+                                         bool harmony_block_scoping);
 };
 
 // ----------------------------------------------------------------------------
@@ -435,6 +437,7 @@
   void ReportMessageAt(Scanner::Location loc,
                        const char* message,
                        Vector<Handle<String> > args);
+  void SetHarmonyBlockScoping(bool block_scoping);
 
  private:
   // Limit on number of function parameters is chosen arbitrarily.
@@ -451,6 +454,12 @@
     PARSE_EAGERLY
   };
 
+  enum VariableDeclarationContext {
+    kSourceElement,
+    kStatement,
+    kForStatement
+  };
+
   Isolate* isolate() { return isolate_; }
   Zone* zone() { return isolate_->zone(); }
 
@@ -479,12 +488,15 @@
   // for failure at the call sites.
   void* ParseSourceElements(ZoneList<Statement*>* processor,
                             int end_token, bool* ok);
+  Statement* ParseSourceElement(ZoneStringList* labels, bool* ok);
   Statement* ParseStatement(ZoneStringList* labels, bool* ok);
   Statement* ParseFunctionDeclaration(bool* ok);
   Statement* ParseNativeDeclaration(bool* ok);
   Block* ParseBlock(ZoneStringList* labels, bool* ok);
-  Block* ParseVariableStatement(bool* ok);
-  Block* ParseVariableDeclarations(bool accept_IN,
+  Block* ParseScopedBlock(ZoneStringList* labels, bool* ok);
+  Block* ParseVariableStatement(VariableDeclarationContext var_context,
+                                bool* ok);
+  Block* ParseVariableDeclarations(VariableDeclarationContext var_context,
                                    Handle<String>* out,
                                    bool* ok);
   Statement* ParseExpressionOrLabelledStatement(ZoneStringList* labels,
@@ -493,7 +505,6 @@
   Statement* ParseContinueStatement(bool* ok);
   Statement* ParseBreakStatement(ZoneStringList* labels, bool* ok);
   Statement* ParseReturnStatement(bool* ok);
-  Block* WithHelper(Expression* obj, ZoneStringList* labels, bool* ok);
   Statement* ParseWithStatement(ZoneStringList* labels, bool* ok);
   CaseClause* ParseCaseClause(bool* default_seen_ptr, bool* ok);
   SwitchStatement* ParseSwitchStatement(ZoneStringList* labels, bool* ok);
@@ -715,6 +726,7 @@
   // Heuristically that means that the function will be called immediately,
   // so never lazily compile it.
   bool parenthesized_function_;
+  bool harmony_block_scoping_;
 
   friend class LexicalScope;
 };
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index 5f283c3..85a5e4f 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -166,6 +166,18 @@
 }
 
 
+void OS::ProtectCode(void* address, const size_t size) {
+  DWORD old_protect;
+  VirtualProtect(address, size, PAGE_EXECUTE_READ, &old_protect);
+}
+
+
+void OS::Guard(void* address, const size_t size) {
+  DWORD oldprotect;
+  VirtualProtect(address, size, PAGE_READONLY | PAGE_GUARD, &oldprotect);
+}
+
+
 void OS::Sleep(int milliseconds) {
   unsigned int ms = static_cast<unsigned int>(milliseconds);
   usleep(1000 * ms);
diff --git a/src/platform-linux.cc b/src/platform-linux.cc
index 37330be..362bf47 100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -676,9 +676,11 @@
   // This is also initialized by the first argument to pthread_create() but we
   // don't know which thread will run first (the original thread or the new
   // one) so we initialize it here too.
+#ifdef PR_SET_NAME
   prctl(PR_SET_NAME,
         reinterpret_cast<unsigned long>(thread->name()),  // NOLINT
         0, 0, 0);
+#endif
   thread->data()->thread_ = pthread_self();
   ASSERT(thread->data()->thread_ != kNoThread);
   thread->Run();
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 1ea53c8..52cf029 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -70,6 +70,7 @@
 }
 
 
+#ifndef __CYGWIN__
 // Get rid of writable permission on code allocations.
 void OS::ProtectCode(void* address, const size_t size) {
   mprotect(address, size, PROT_READ | PROT_EXEC);
@@ -80,6 +81,7 @@
 void OS::Guard(void* address, const size_t size) {
   mprotect(address, size, PROT_NONE);
 }
+#endif  // __CYGWIN__
 
 
 // ----------------------------------------------------------------------------
diff --git a/src/preparser-api.cc b/src/preparser-api.cc
index e0ab500..80656d5 100644
--- a/src/preparser-api.cc
+++ b/src/preparser-api.cc
@@ -28,6 +28,7 @@
 #include "../include/v8-preparser.h"
 
 #include "globals.h"
+#include "flags.h"
 #include "checks.h"
 #include "allocation.h"
 #include "utils.h"
diff --git a/src/preparser.cc b/src/preparser.cc
index c741b46..1a3dd73 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -56,8 +56,6 @@
 // That means that contextual checks (like a label being declared where
 // it is used) are generally omitted.
 
-namespace i = ::v8::internal;
-
 void PreParser::ReportUnexpectedToken(i::Token::Value token) {
   // We don't report stack overflows here, to avoid increasing the
   // stack depth even further.  Instead we report it after parsing is
@@ -114,6 +112,16 @@
 #undef DUMMY
 
 
+PreParser::Statement PreParser::ParseSourceElement(bool* ok) {
+  switch (peek()) {
+    case i::Token::LET:
+      return ParseVariableStatement(kSourceElement, ok);
+    default:
+      return ParseStatement(ok);
+  }
+}
+
+
 PreParser::SourceElements PreParser::ParseSourceElements(int end_token,
                                                          bool* ok) {
   // SourceElements ::
@@ -121,7 +129,7 @@
 
   bool allow_directive_prologue = true;
   while (peek() != end_token) {
-    Statement statement = ParseStatement(CHECK_OK);
+    Statement statement = ParseSourceElement(CHECK_OK);
     if (allow_directive_prologue) {
       if (statement.IsUseStrictLiteral()) {
         set_strict_mode();
@@ -174,7 +182,7 @@
 
     case i::Token::CONST:
     case i::Token::VAR:
-      return ParseVariableStatement(ok);
+      return ParseVariableStatement(kStatement, ok);
 
     case i::Token::SEMICOLON:
       Next();
@@ -260,7 +268,7 @@
   Expect(i::Token::LBRACE, CHECK_OK);
   while (peek() != i::Token::RBRACE) {
     i::Scanner::Location start_location = scanner_->peek_location();
-    Statement statement = ParseStatement(CHECK_OK);
+    Statement statement = ParseSourceElement(CHECK_OK);
     i::Scanner::Location end_location = scanner_->location();
     if (strict_mode() && statement.IsFunctionDeclaration()) {
       ReportMessageAt(start_location.beg_pos, end_location.end_pos,
@@ -274,11 +282,15 @@
 }
 
 
-PreParser::Statement PreParser::ParseVariableStatement(bool* ok) {
+PreParser::Statement PreParser::ParseVariableStatement(
+    VariableDeclarationContext var_context,
+    bool* ok) {
   // VariableStatement ::
   //   VariableDeclarations ';'
 
-  Statement result = ParseVariableDeclarations(true, NULL, CHECK_OK);
+  Statement result = ParseVariableDeclarations(var_context,
+                                               NULL,
+                                               CHECK_OK);
   ExpectSemicolon(CHECK_OK);
   return result;
 }
@@ -289,9 +301,10 @@
 // *var is untouched; in particular, it is the caller's responsibility
 // to initialize it properly. This mechanism is also used for the parsing
 // of 'for-in' loops.
-PreParser::Statement PreParser::ParseVariableDeclarations(bool accept_IN,
-                                                          int* num_decl,
-                                                          bool* ok) {
+PreParser::Statement PreParser::ParseVariableDeclarations(
+    VariableDeclarationContext var_context,
+    int* num_decl,
+    bool* ok) {
   // VariableDeclarations ::
   //   ('var' | 'const') (Identifier ('=' AssignmentExpression)?)+[',']
 
@@ -306,13 +319,25 @@
       return Statement::Default();
     }
     Consume(i::Token::CONST);
+  } else if (peek() == i::Token::LET) {
+    if (var_context != kSourceElement &&
+        var_context != kForStatement) {
+      i::Scanner::Location location = scanner_->peek_location();
+      ReportMessageAt(location.beg_pos, location.end_pos,
+                      "unprotected_let", NULL);
+      *ok = false;
+      return Statement::Default();
+    }
+    Consume(i::Token::LET);
   } else {
     *ok = false;
     return Statement::Default();
   }
 
-  // The scope of a variable/const declared anywhere inside a function
-  // is the entire function (ECMA-262, 3rd, 10.1.3, and 12.2). .
+  // The scope of a var/const declared variable anywhere inside a function
+  // is the entire function (ECMA-262, 3rd, 10.1.3, and 12.2). The scope
+  // of a let declared variable is the scope of the immediately enclosing
+  // block.
   int nvars = 0;  // the number of variables declared
   do {
     // Parse variable name.
@@ -328,7 +353,7 @@
     nvars++;
     if (peek() == i::Token::ASSIGN) {
       Expect(i::Token::ASSIGN, CHECK_OK);
-      ParseAssignmentExpression(accept_IN, CHECK_OK);
+      ParseAssignmentExpression(var_context != kForStatement, CHECK_OK);
     }
   } while (peek() == i::Token::COMMA);
 
@@ -537,9 +562,10 @@
   Expect(i::Token::FOR, CHECK_OK);
   Expect(i::Token::LPAREN, CHECK_OK);
   if (peek() != i::Token::SEMICOLON) {
-    if (peek() == i::Token::VAR || peek() == i::Token::CONST) {
+    if (peek() == i::Token::VAR || peek() == i::Token::CONST ||
+        peek() == i::Token::LET) {
       int decl_count;
-      ParseVariableDeclarations(false, &decl_count, CHECK_OK);
+      ParseVariableDeclarations(kForStatement, &decl_count, CHECK_OK);
       if (peek() == i::Token::IN && decl_count == 1) {
         Expect(i::Token::IN, CHECK_OK);
         ParseExpression(true, CHECK_OK);
diff --git a/src/preparser.h b/src/preparser.h
index 3d72c97..cd0a530 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -77,6 +77,12 @@
     kFunctionScope
   };
 
+  enum VariableDeclarationContext {
+    kSourceElement,
+    kStatement,
+    kForStatement
+  };
+
   class Expression;
 
   class Identifier {
@@ -344,7 +350,8 @@
         strict_mode_violation_type_(NULL),
         stack_overflow_(false),
         allow_lazy_(true),
-        parenthesized_function_(false) { }
+        parenthesized_function_(false),
+        harmony_block_scoping_(scanner->HarmonyBlockScoping()) { }
 
   // Preparse the program. Only called in PreParseProgram after creating
   // the instance.
@@ -377,12 +384,16 @@
   // which is set to false if parsing failed; it is unchanged otherwise.
   // By making the 'exception handling' explicit, we are forced to check
   // for failure at the call sites.
+  Statement ParseSourceElement(bool* ok);
   SourceElements ParseSourceElements(int end_token, bool* ok);
   Statement ParseStatement(bool* ok);
   Statement ParseFunctionDeclaration(bool* ok);
   Statement ParseBlock(bool* ok);
-  Statement ParseVariableStatement(bool* ok);
-  Statement ParseVariableDeclarations(bool accept_IN, int* num_decl, bool* ok);
+  Statement ParseVariableStatement(VariableDeclarationContext var_context,
+                                   bool* ok);
+  Statement ParseVariableDeclarations(VariableDeclarationContext var_context,
+                                      int* num_decl,
+                                      bool* ok);
   Statement ParseExpressionOrLabelledStatement(bool* ok);
   Statement ParseIfStatement(bool* ok);
   Statement ParseContinueStatement(bool* ok);
@@ -496,6 +507,7 @@
   bool stack_overflow_;
   bool allow_lazy_;
   bool parenthesized_function_;
+  bool harmony_block_scoping_;
 };
 } }  // v8::preparser
 
diff --git a/src/prettyprinter.cc b/src/prettyprinter.cc
index f18b320..b034293 100644
--- a/src/prettyprinter.cc
+++ b/src/prettyprinter.cc
@@ -123,11 +123,11 @@
 }
 
 
-void PrettyPrinter::VisitEnterWithContextStatement(
-    EnterWithContextStatement* node) {
-  Print("<enter with context> (");
+void PrettyPrinter::VisitWithStatement(WithStatement* node) {
+  Print("with (");
   Visit(node->expression());
   Print(") ");
+  Visit(node->statement());
 }
 
 
@@ -798,9 +798,10 @@
 }
 
 
-void AstPrinter::VisitEnterWithContextStatement(
-    EnterWithContextStatement* node) {
-  PrintIndentedVisit("ENTER WITH CONTEXT", node->expression());
+void AstPrinter::VisitWithStatement(WithStatement* node) {
+  IndentedScope indent(this, "WITH");
+  PrintIndentedVisit("OBJECT", node->expression());
+  PrintIndentedVisit("BODY", node->statement());
 }
 
 
@@ -1194,10 +1195,10 @@
 }
 
 
-void JsonAstBuilder::VisitEnterWithContextStatement(
-    EnterWithContextStatement* stmt) {
-  TagScope tag(this, "EnterWithContextStatement");
+void JsonAstBuilder::VisitWithStatement(WithStatement* stmt) {
+  TagScope tag(this, "WithStatement");
   Visit(stmt->expression());
+  Visit(stmt->statement());
 }
 
 
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 07426f2..5a95445 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -983,6 +983,11 @@
 }
 
 
+Handle<HeapObject> HeapEntry::GetHeapObject() {
+  return snapshot_->collection()->FindHeapObjectById(id());
+}
+
+
 template<class Visitor>
 void HeapEntry::ApplyAndPaintAllReachable(Visitor* visitor) {
   List<HeapEntry*> list(10);
@@ -1195,12 +1200,9 @@
                                    int children_count,
                                    int retainers_count) {
   ASSERT(raw_entries_ == NULL);
-  raw_entries_ = NewArray<char>(
-      HeapEntry::EntriesSize(entries_count, children_count, retainers_count));
-#ifdef DEBUG
   raw_entries_size_ =
       HeapEntry::EntriesSize(entries_count, children_count, retainers_count);
-#endif
+  raw_entries_ = NewArray<char>(raw_entries_size_);
 }
 
 
@@ -1346,8 +1348,8 @@
 
 
 void HeapObjectsMap::SnapshotGenerationFinished() {
-    initial_fill_mode_ = false;
-    RemoveDeadEntries();
+  initial_fill_mode_ = false;
+  RemoveDeadEntries();
 }
 
 
@@ -1493,6 +1495,24 @@
 }
 
 
+Handle<HeapObject> HeapSnapshotsCollection::FindHeapObjectById(uint64_t id) {
+  AssertNoAllocation no_allocation;
+  HeapObject* object = NULL;
+  HeapIterator iterator(HeapIterator::kFilterUnreachable);
+  // Make sure that object with the given id is still reachable.
+  for (HeapObject* obj = iterator.next();
+       obj != NULL;
+       obj = iterator.next()) {
+    if (ids_.FindObject(obj->address()) == id) {
+      ASSERT(object == NULL);
+      object = obj;
+      // Can't break -- kFilterUnreachable requires full heap traversal.
+    }
+  }
+  return object != NULL ? Handle<HeapObject>(object) : Handle<HeapObject>();
+}
+
+
 HeapEntry *const HeapEntriesMap::kHeapEntryPlaceholder =
     reinterpret_cast<HeapEntry*>(1);
 
@@ -1663,7 +1683,7 @@
   } else if (object->IsJSGlobalObject()) {
     const char* tag = objects_tags_.GetTag(object);
     const char* name = collection_->names()->GetName(
-        GetConstructorNameForHeapProfile(JSObject::cast(object)));
+        GetConstructorName(JSObject::cast(object)));
     if (tag != NULL) {
       name = collection_->names()->GetFormatted("%s / %s", name, tag);
     }
@@ -1691,8 +1711,7 @@
     return AddEntry(object,
                     HeapEntry::kObject,
                     collection_->names()->GetName(
-                        GetConstructorNameForHeapProfile(
-                            JSObject::cast(object))),
+                        GetConstructorName(JSObject::cast(object))),
                     children_count,
                     retainers_count);
   } else if (object->IsString()) {
@@ -2101,6 +2120,31 @@
 }
 
 
+String* V8HeapExplorer::GetConstructorName(JSObject* object) {
+  if (object->IsJSFunction()) return HEAP->closure_symbol();
+  String* constructor_name = object->constructor_name();
+  if (constructor_name == HEAP->Object_symbol()) {
+    // Look up an immediate "constructor" property, if it is a function,
+    // return its name. This is for instances of binding objects, which
+    // have prototype constructor type "Object".
+    Object* constructor_prop = NULL;
+    LookupResult result;
+    object->LocalLookupRealNamedProperty(HEAP->constructor_symbol(), &result);
+    if (result.IsProperty()) {
+      constructor_prop = result.GetLazyValue();
+    }
+    if (constructor_prop->IsJSFunction()) {
+      Object* maybe_name = JSFunction::cast(constructor_prop)->shared()->name();
+      if (maybe_name->IsString()) {
+        String* name = String::cast(maybe_name);
+        if (name->length() > 0) return name;
+      }
+    }
+  }
+  return object->constructor_name();
+}
+
+
 HeapEntry* V8HeapExplorer::GetEntry(Object* obj) {
   if (!obj->IsHeapObject()) return NULL;
   return filler_->FindOrAddEntry(obj, this);
@@ -2960,10 +3004,19 @@
   bool aborted_;
 };
 
+const int HeapSnapshotJSONSerializer::kMaxSerializableSnapshotRawSize =
+    256 * MB;
+
 void HeapSnapshotJSONSerializer::Serialize(v8::OutputStream* stream) {
   ASSERT(writer_ == NULL);
   writer_ = new OutputStreamWriter(stream);
 
+  HeapSnapshot* original_snapshot = NULL;
+  if (snapshot_->raw_entries_size() >= kMaxSerializableSnapshotRawSize) {
+    // The snapshot is too big. Serialize a fake snapshot.
+    original_snapshot = snapshot_;
+    snapshot_ = CreateFakeSnapshot();
+  }
   // Since nodes graph is cyclic, we need the first pass to enumerate
   // them. Strings can be serialized in one pass.
   EnumerateNodes();
@@ -2971,6 +3024,26 @@
 
   delete writer_;
   writer_ = NULL;
+
+  if (original_snapshot != NULL) {
+    delete snapshot_;
+    snapshot_ = original_snapshot;
+  }
+}
+
+
+HeapSnapshot* HeapSnapshotJSONSerializer::CreateFakeSnapshot() {
+  HeapSnapshot* result = new HeapSnapshot(snapshot_->collection(),
+                                          HeapSnapshot::kFull,
+                                          snapshot_->title(),
+                                          snapshot_->uid());
+  result->AllocateEntries(2, 1, 0);
+  HeapEntry* root = result->AddRootEntry(1);
+  HeapEntry* message = result->AddEntry(
+      HeapEntry::kString, "The snapshot is too big", 0, 4, 0, 0);
+  root->SetUnidirElementReference(0, 1, message);
+  result->SetDominatorsToSelf();
+  return result;
 }
 
 
@@ -3250,10 +3323,4 @@
   sorted_entries->Sort(SortUsingEntryValue);
 }
 
-
-String* GetConstructorNameForHeapProfile(JSObject* object) {
-  if (object->IsJSFunction()) return HEAP->closure_symbol();
-  return object->constructor_name();
-}
-
 } }  // namespace v8::internal
diff --git a/src/profile-generator.h b/src/profile-generator.h
index d1c2b38..fbb6fab 100644
--- a/src/profile-generator.h
+++ b/src/profile-generator.h
@@ -584,6 +584,8 @@
 
   void Print(int max_depth, int indent);
 
+  Handle<HeapObject> GetHeapObject();
+
   static int EntriesSize(int entries_count,
                          int children_count,
                          int retainers_count);
@@ -654,6 +656,7 @@
   HeapEntry* gc_roots() { return gc_roots_entry_; }
   HeapEntry* natives_root() { return natives_root_entry_; }
   List<HeapEntry*>* entries() { return &entries_; }
+  int raw_entries_size() { return raw_entries_size_; }
 
   void AllocateEntries(
       int entries_count, int children_count, int retainers_count);
@@ -689,9 +692,7 @@
   char* raw_entries_;
   List<HeapEntry*> entries_;
   bool entries_sorted_;
-#ifdef DEBUG
   int raw_entries_size_;
-#endif
 
   friend class HeapSnapshotTester;
 
@@ -763,6 +764,7 @@
   TokenEnumerator* token_enumerator() { return token_enumerator_; }
 
   uint64_t GetObjectId(Address addr) { return ids_.FindObject(addr); }
+  Handle<HeapObject> FindHeapObjectById(uint64_t id);
   void ObjectMoveEvent(Address from, Address to) { ids_.MoveObject(from, to); }
 
  private:
@@ -921,6 +923,8 @@
   bool IterateAndExtractReferences(SnapshotFillerInterface* filler);
   void TagGlobalObjects();
 
+  static String* GetConstructorName(JSObject* object);
+
   static HeapObject* const kInternalRootObject;
 
  private:
@@ -1095,6 +1099,7 @@
   }
 
   void EnumerateNodes();
+  HeapSnapshot* CreateFakeSnapshot();
   int GetNodeId(HeapEntry* entry);
   int GetStringId(const char* s);
   void SerializeEdge(HeapGraphEdge* edge);
@@ -1106,6 +1111,8 @@
   void SerializeStrings();
   void SortHashMap(HashMap* map, List<HashMap::Entry*>* sorted_entries);
 
+  static const int kMaxSerializableSnapshotRawSize;
+
   HeapSnapshot* snapshot_;
   HashMap nodes_;
   HashMap strings_;
@@ -1119,9 +1126,6 @@
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
 };
 
-
-String* GetConstructorNameForHeapProfile(JSObject* object);
-
 } }  // namespace v8::internal
 
 #endif  // V8_PROFILE_GENERATOR_H_
diff --git a/src/proxy.js b/src/proxy.js
index 27524bd..2839159 100644
--- a/src/proxy.js
+++ b/src/proxy.js
@@ -136,6 +136,10 @@
   return !!this.getPropertyDescriptor(name)
 }
 
+function DerivedHasOwnTrap(name) {
+  return !!this.getOwnPropertyDescriptor(name)
+}
+
 function DerivedKeysTrap() {
   var names = this.getOwnPropertyNames()
   var enumerableNames = []
diff --git a/src/regexp-macro-assembler.cc b/src/regexp-macro-assembler.cc
index 5578243..f91ea93 100644
--- a/src/regexp-macro-assembler.cc
+++ b/src/regexp-macro-assembler.cc
@@ -120,27 +120,31 @@
   String* subject_ptr = *subject;
   // Character offsets into string.
   int start_offset = previous_index;
-  int end_offset = subject_ptr->length();
+  int char_length = subject_ptr->length() - start_offset;
+  int slice_offset = 0;
 
-  // The string has been flattened, so it it is a cons string it contains the
+  // The string has been flattened, so if it is a cons string it contains the
   // full string in the first part.
   if (StringShape(subject_ptr).IsCons()) {
     ASSERT_EQ(0, ConsString::cast(subject_ptr)->second()->length());
     subject_ptr = ConsString::cast(subject_ptr)->first();
+  } else if (StringShape(subject_ptr).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(subject_ptr);
+    subject_ptr = slice->parent();
+    slice_offset = slice->offset();
   }
   // Ensure that an underlying string has the same ascii-ness.
   bool is_ascii = subject_ptr->IsAsciiRepresentation();
   ASSERT(subject_ptr->IsExternalString() || subject_ptr->IsSeqString());
   // String is now either Sequential or External
   int char_size_shift = is_ascii ? 0 : 1;
-  int char_length = end_offset - start_offset;
 
   const byte* input_start =
-      StringCharacterPosition(subject_ptr, start_offset);
+      StringCharacterPosition(subject_ptr, start_offset + slice_offset);
   int byte_length = char_length << char_size_shift;
   const byte* input_end = input_start + byte_length;
   Result res = Execute(*regexp_code,
-                       subject_ptr,
+                       *subject,
                        start_offset,
                        input_start,
                        input_end,
@@ -152,7 +156,7 @@
 
 NativeRegExpMacroAssembler::Result NativeRegExpMacroAssembler::Execute(
     Code* code,
-    String* input,
+    String* input,  // This needs to be the unpacked (sliced, cons) string.
     int start_offset,
     const byte* input_start,
     const byte* input_end,
diff --git a/src/regexp.js b/src/regexp.js
index 7b851a3..a7f42d5 100644
--- a/src/regexp.js
+++ b/src/regexp.js
@@ -50,24 +50,29 @@
   var global = false;
   var ignoreCase = false;
   var multiline = false;
-
   for (var i = 0; i < flags.length; i++) {
     var c = %_CallFunction(flags, i, StringCharAt);
     switch (c) {
       case 'g':
-        // Allow duplicate flags to be consistent with JSC and others.
+        if (global) {
+          throw MakeSyntaxError("invalid_regexp_flags", [flags]);
+        }
         global = true;
         break;
       case 'i':
+        if (ignoreCase) {
+          throw MakeSyntaxError("invalid_regexp_flags", [flags]);
+        }
         ignoreCase = true;
         break;
       case 'm':
+        if (multiline) {
+          throw MakeSyntaxError("invalid_regexp_flags", [flags]);
+        }
         multiline = true;
         break;
       default:
-        // Ignore flags that have no meaning to be consistent with
-        // JSC.
-        break;
+        throw MakeSyntaxError("invalid_regexp_flags", [flags]);
     }
   }
 
diff --git a/src/rewriter.cc b/src/rewriter.cc
index e8ca5b9..ad6ce05 100644
--- a/src/rewriter.cc
+++ b/src/rewriter.cc
@@ -197,13 +197,17 @@
 }
 
 
+void Processor::VisitWithStatement(WithStatement* node) {
+  bool set_after_body = is_set_;
+  Visit(node->statement());
+  is_set_ = is_set_ && set_after_body;
+}
+
+
 // Do nothing:
 void Processor::VisitDeclaration(Declaration* node) {}
 void Processor::VisitEmptyStatement(EmptyStatement* node) {}
 void Processor::VisitReturnStatement(ReturnStatement* node) {}
-void Processor::VisitEnterWithContextStatement(
-    EnterWithContextStatement* node) {
-}
 void Processor::VisitExitContextStatement(ExitContextStatement* node) {}
 void Processor::VisitDebuggerStatement(DebuggerStatement* node) {}
 
diff --git a/src/runtime-profiler.h b/src/runtime-profiler.h
index 3f3ab07..15c2097 100644
--- a/src/runtime-profiler.h
+++ b/src/runtime-profiler.h
@@ -94,12 +94,6 @@
 
  private:
   static const int kSamplerWindowSize = 16;
-  static const int kStateWindowSize = 128;
-
-  enum SamplerState {
-    IN_NON_JS_STATE = 0,
-    IN_JS_STATE = 1
-  };
 
   static void HandleWakeUp(Isolate* isolate);
 
diff --git a/src/runtime.cc b/src/runtime.cc
index 8f14565..50f9ce1 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -219,8 +219,20 @@
       }
       break;
     }
-    default:
-      UNREACHABLE();
+    case JSObject::NON_STRICT_ARGUMENTS_ELEMENTS:
+      UNIMPLEMENTED();
+      break;
+    case JSObject::EXTERNAL_PIXEL_ELEMENTS:
+    case JSObject::EXTERNAL_BYTE_ELEMENTS:
+    case JSObject::EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
+    case JSObject::EXTERNAL_SHORT_ELEMENTS:
+    case JSObject::EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
+    case JSObject::EXTERNAL_INT_ELEMENTS:
+    case JSObject::EXTERNAL_UNSIGNED_INT_ELEMENTS:
+    case JSObject::EXTERNAL_FLOAT_ELEMENTS:
+    case JSObject::EXTERNAL_DOUBLE_ELEMENTS:
+    case JSObject::FAST_DOUBLE_ELEMENTS:
+      // No contained objects, nothing to do.
       break;
   }
   return copy;
@@ -618,7 +630,44 @@
   ASSERT(args.length() == 1);
   CONVERT_CHECKED(JSProxy, proxy, args[0]);
   proxy->Fix();
-  return proxy;
+  return isolate->heap()->undefined_value();
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapInitialize) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 1);
+  CONVERT_ARG_CHECKED(JSWeakMap, weakmap, 0);
+  ASSERT(weakmap->map()->inobject_properties() == 0);
+  Handle<ObjectHashTable> table = isolate->factory()->NewObjectHashTable(0);
+  weakmap->set_table(*table);
+  weakmap->set_next(Smi::FromInt(0));
+  return *weakmap;
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapGet) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 2);
+  CONVERT_ARG_CHECKED(JSWeakMap, weakmap, 0);
+  // TODO(mstarzinger): Currently we cannot use JSProxy objects as keys
+  // because they cannot be cast to JSObject to get an identity hash code.
+  CONVERT_ARG_CHECKED(JSObject, key, 1);
+  return weakmap->table()->Lookup(*key);
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapSet) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 3);
+  CONVERT_ARG_CHECKED(JSWeakMap, weakmap, 0);
+  // TODO(mstarzinger): See Runtime_WeakMapGet above.
+  CONVERT_ARG_CHECKED(JSObject, key, 1);
+  Handle<Object> value(args[2]);
+  Handle<ObjectHashTable> table(weakmap->table());
+  Handle<ObjectHashTable> new_table = PutIntoObjectHashTable(table, key, value);
+  weakmap->set_table(*new_table);
+  return *value;
 }
 
 
@@ -1257,8 +1306,9 @@
   int index;
   PropertyAttributes attributes;
   ContextLookupFlags flags = DONT_FOLLOW_CHAINS;
+  BindingFlags binding_flags;
   Handle<Object> holder =
-      context->Lookup(name, flags, &index, &attributes);
+      context->Lookup(name, flags, &index, &attributes, &binding_flags);
 
   if (attributes != ABSENT) {
     // The name was declared before; check for conflicting
@@ -1545,8 +1595,9 @@
   int index;
   PropertyAttributes attributes;
   ContextLookupFlags flags = FOLLOW_CHAINS;
+  BindingFlags binding_flags;
   Handle<Object> holder =
-      context->Lookup(name, flags, &index, &attributes);
+      context->Lookup(name, flags, &index, &attributes, &binding_flags);
 
   // In most situations, the property introduced by the const
   // declaration should be present in the context extension object.
@@ -1673,7 +1724,9 @@
 RUNTIME_FUNCTION(MaybeObject*, Runtime_RegExpConstructResult) {
   ASSERT(args.length() == 3);
   CONVERT_SMI_ARG_CHECKED(elements_count, 0);
-  if (elements_count > JSArray::kMaxFastElementsLength) {
+  if (elements_count < 0 ||
+      elements_count > FixedArray::kMaxLength ||
+      !Smi::IsValid(elements_count)) {
     return isolate->ThrowIllegalOperation();
   }
   Object* new_object;
@@ -1815,10 +1868,19 @@
 }
 
 
-RUNTIME_FUNCTION(MaybeObject*, Runtime_GetGlobalReceiver) {
-  // Returns a real global receiver, not one of builtins object.
+RUNTIME_FUNCTION(MaybeObject*, Runtime_GetDefaultReceiver) {
+  NoHandleAllocation handle_free;
+  ASSERT(args.length() == 1);
+  CONVERT_CHECKED(JSFunction, function, args[0]);
+  SharedFunctionInfo* shared = function->shared();
+  if (shared->native() || shared->strict_mode()) {
+    return isolate->heap()->undefined_value();
+  }
+  // Returns undefined for strict or native functions, or
+  // the associated global receiver for "normal" functions.
+
   Context* global_context =
-      isolate->context()->global()->global_context();
+      function->context()->global()->global_context();
   return global_context->global()->global_receiver();
 }
 
@@ -1978,6 +2040,24 @@
 }
 
 
+// Creates a local, readonly, property called length with the correct
+// length (when read by the user). This effectively overwrites the
+// interceptor used to normally provide the length.
+RUNTIME_FUNCTION(MaybeObject*, Runtime_BoundFunctionSetLength) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 2);
+  CONVERT_CHECKED(JSFunction, fun, args[0]);
+  CONVERT_CHECKED(Smi, length, args[1]);
+  MaybeObject* maybe_name =
+      isolate->heap()->AllocateStringFromAscii(CStrVector("length"));
+  String* name;
+  if (!maybe_name->To(&name)) return maybe_name;
+  PropertyAttributes attr =
+      static_cast<PropertyAttributes>(DONT_DELETE | DONT_ENUM | READ_ONLY);
+  return fun->AddProperty(name, length, attr, kNonStrictMode);
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_FunctionSetPrototype) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
@@ -1993,6 +2073,61 @@
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_FunctionSetReadOnlyPrototype) {
+  NoHandleAllocation ha;
+  RUNTIME_ASSERT(args.length() == 1);
+  CONVERT_CHECKED(JSFunction, function, args[0]);
+
+  MaybeObject* maybe_name =
+      isolate->heap()->AllocateStringFromAscii(CStrVector("prototype"));
+  String* name;
+  if (!maybe_name->To(&name)) return maybe_name;
+
+  if (function->HasFastProperties()) {
+    // Construct a new field descriptor with updated attributes.
+    DescriptorArray* instance_desc = function->map()->instance_descriptors();
+    int index = instance_desc->Search(name);
+    ASSERT(index != DescriptorArray::kNotFound);
+    PropertyDetails details(instance_desc->GetDetails(index));
+    CallbacksDescriptor new_desc(name,
+        instance_desc->GetValue(index),
+        static_cast<PropertyAttributes>(details.attributes() | READ_ONLY),
+        details.index());
+    // Construct a new field descriptors array containing the new descriptor.
+    Object* descriptors_unchecked;
+    { MaybeObject* maybe_descriptors_unchecked =
+        instance_desc->CopyInsert(&new_desc, REMOVE_TRANSITIONS);
+      if (!maybe_descriptors_unchecked->ToObject(&descriptors_unchecked)) {
+        return maybe_descriptors_unchecked;
+      }
+    }
+    DescriptorArray* new_descriptors =
+        DescriptorArray::cast(descriptors_unchecked);
+    // Create a new map featuring the new field descriptors array.
+    Object* map_unchecked;
+    { MaybeObject* maybe_map_unchecked = function->map()->CopyDropDescriptors();
+      if (!maybe_map_unchecked->ToObject(&map_unchecked)) {
+        return maybe_map_unchecked;
+      }
+    }
+    Map* new_map = Map::cast(map_unchecked);
+    new_map->set_instance_descriptors(new_descriptors);
+    function->set_map(new_map);
+  } else {  // Dictionary properties.
+    // Directly manipulate the property details.
+    int entry = function->property_dictionary()->FindEntry(name);
+    ASSERT(entry != StringDictionary::kNotFound);
+    PropertyDetails details = function->property_dictionary()->DetailsAt(entry);
+    PropertyDetails new_details(
+        static_cast<PropertyAttributes>(details.attributes() | READ_ONLY),
+        details.type(),
+        details.index());
+    function->property_dictionary()->DetailsAtPut(entry, new_details);
+  }
+  return function;
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_FunctionIsAPIFunction) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
@@ -2549,21 +2684,22 @@
 void CompiledReplacement::Compile(Handle<String> replacement,
                                   int capture_count,
                                   int subject_length) {
-  ASSERT(replacement->IsFlat());
-  if (replacement->IsAsciiRepresentation()) {
+  {
     AssertNoAllocation no_alloc;
-    ParseReplacementPattern(&parts_,
-                            replacement->ToAsciiVector(),
-                            capture_count,
-                            subject_length);
-  } else {
-    ASSERT(replacement->IsTwoByteRepresentation());
-    AssertNoAllocation no_alloc;
-
-    ParseReplacementPattern(&parts_,
-                            replacement->ToUC16Vector(),
-                            capture_count,
-                            subject_length);
+    String::FlatContent content = replacement->GetFlatContent();
+    ASSERT(content.IsFlat());
+    if (content.IsAscii()) {
+      ParseReplacementPattern(&parts_,
+                              content.ToAsciiVector(),
+                              capture_count,
+                              subject_length);
+    } else {
+      ASSERT(content.IsTwoByte());
+      ParseReplacementPattern(&parts_,
+                              content.ToUC16Vector(),
+                              capture_count,
+                              subject_length);
+    }
   }
   Isolate* isolate = replacement->GetIsolate();
   // Find substrings of replacement string and create them as String objects.
@@ -2935,34 +3071,32 @@
 
   AssertNoAllocation no_heap_allocation;  // ensure vectors stay valid
   // Extract flattened substrings of cons strings before determining asciiness.
-  String* seq_sub = *sub;
-  if (seq_sub->IsConsString()) seq_sub = ConsString::cast(seq_sub)->first();
-  String* seq_pat = *pat;
-  if (seq_pat->IsConsString()) seq_pat = ConsString::cast(seq_pat)->first();
+  String::FlatContent seq_sub = sub->GetFlatContent();
+  String::FlatContent seq_pat = pat->GetFlatContent();
 
   // dispatch on type of strings
-  if (seq_pat->IsAsciiRepresentation()) {
-    Vector<const char> pat_vector = seq_pat->ToAsciiVector();
-    if (seq_sub->IsAsciiRepresentation()) {
+  if (seq_pat.IsAscii()) {
+    Vector<const char> pat_vector = seq_pat.ToAsciiVector();
+    if (seq_sub.IsAscii()) {
       return SearchString(isolate,
-                          seq_sub->ToAsciiVector(),
+                          seq_sub.ToAsciiVector(),
                           pat_vector,
                           start_index);
     }
     return SearchString(isolate,
-                        seq_sub->ToUC16Vector(),
+                        seq_sub.ToUC16Vector(),
                         pat_vector,
                         start_index);
   }
-  Vector<const uc16> pat_vector = seq_pat->ToUC16Vector();
-  if (seq_sub->IsAsciiRepresentation()) {
+  Vector<const uc16> pat_vector = seq_pat.ToUC16Vector();
+  if (seq_sub.IsAscii()) {
     return SearchString(isolate,
-                        seq_sub->ToAsciiVector(),
+                        seq_sub.ToAsciiVector(),
                         pat_vector,
                         start_index);
   }
   return SearchString(isolate,
-                      seq_sub->ToUC16Vector(),
+                      seq_sub.ToUC16Vector(),
                       pat_vector,
                       start_index);
 }
@@ -3045,29 +3179,31 @@
   if (!sub->IsFlat()) FlattenString(sub);
   if (!pat->IsFlat()) FlattenString(pat);
 
+  int position = -1;
   AssertNoAllocation no_heap_allocation;  // ensure vectors stay valid
 
-  int position = -1;
+  String::FlatContent sub_content = sub->GetFlatContent();
+  String::FlatContent pat_content = pat->GetFlatContent();
 
-  if (pat->IsAsciiRepresentation()) {
-    Vector<const char> pat_vector = pat->ToAsciiVector();
-    if (sub->IsAsciiRepresentation()) {
-      position = StringMatchBackwards(sub->ToAsciiVector(),
+  if (pat_content.IsAscii()) {
+    Vector<const char> pat_vector = pat_content.ToAsciiVector();
+    if (sub_content.IsAscii()) {
+      position = StringMatchBackwards(sub_content.ToAsciiVector(),
                                       pat_vector,
                                       start_index);
     } else {
-      position = StringMatchBackwards(sub->ToUC16Vector(),
+      position = StringMatchBackwards(sub_content.ToUC16Vector(),
                                       pat_vector,
                                       start_index);
     }
   } else {
-    Vector<const uc16> pat_vector = pat->ToUC16Vector();
-    if (sub->IsAsciiRepresentation()) {
-      position = StringMatchBackwards(sub->ToAsciiVector(),
+    Vector<const uc16> pat_vector = pat_content.ToUC16Vector();
+    if (sub_content.IsAscii()) {
+      position = StringMatchBackwards(sub_content.ToAsciiVector(),
                                       pat_vector,
                                       start_index);
     } else {
-      position = StringMatchBackwards(sub->ToUC16Vector(),
+      position = StringMatchBackwards(sub_content.ToUC16Vector(),
                                       pat_vector,
                                       start_index);
     }
@@ -3285,36 +3421,38 @@
   for (;;) {  // Break when search complete.
     builder->EnsureCapacity(kMaxBuilderEntriesPerRegExpMatch);
     AssertNoAllocation no_gc;
-    if (subject->IsAsciiRepresentation()) {
-      Vector<const char> subject_vector = subject->ToAsciiVector();
-      if (pattern->IsAsciiRepresentation()) {
+    String::FlatContent subject_content = subject->GetFlatContent();
+    String::FlatContent pattern_content = pattern->GetFlatContent();
+    if (subject_content.IsAscii()) {
+      Vector<const char> subject_vector = subject_content.ToAsciiVector();
+      if (pattern_content.IsAscii()) {
         if (SearchStringMultiple(isolate,
                                  subject_vector,
-                                 pattern->ToAsciiVector(),
+                                 pattern_content.ToAsciiVector(),
                                  *pattern,
                                  builder,
                                  &match_pos)) break;
       } else {
         if (SearchStringMultiple(isolate,
                                  subject_vector,
-                                 pattern->ToUC16Vector(),
+                                 pattern_content.ToUC16Vector(),
                                  *pattern,
                                  builder,
                                  &match_pos)) break;
       }
     } else {
-      Vector<const uc16> subject_vector = subject->ToUC16Vector();
-      if (pattern->IsAsciiRepresentation()) {
+      Vector<const uc16> subject_vector = subject_content.ToUC16Vector();
+      if (pattern_content.IsAscii()) {
         if (SearchStringMultiple(isolate,
                                  subject_vector,
-                                 pattern->ToAsciiVector(),
+                                 pattern_content.ToAsciiVector(),
                                  *pattern,
                                  builder,
                                  &match_pos)) break;
       } else {
         if (SearchStringMultiple(isolate,
                                  subject_vector,
-                                 pattern->ToUC16Vector(),
+                                 pattern_content.ToUC16Vector(),
                                  *pattern,
                                  builder,
                                  &match_pos)) break;
@@ -3547,7 +3685,7 @@
   HandleScope handles(isolate);
 
   CONVERT_ARG_CHECKED(String, subject, 1);
-  if (!subject->IsFlat()) { FlattenString(subject); }
+  if (!subject->IsFlat()) FlattenString(subject);
   CONVERT_ARG_CHECKED(JSRegExp, regexp, 0);
   CONVERT_ARG_CHECKED(JSArray, last_match_info, 2);
   CONVERT_ARG_CHECKED(JSArray, result_array, 3);
@@ -4498,7 +4636,7 @@
   for (int i = 0; i < length; i++) {
     jsproto->GetLocalPropertyNames(*names, next_copy_index);
     next_copy_index += local_property_count[i];
-    if (!GetHiddenProperties(jsproto, false)->IsUndefined()) {
+    if (jsproto->HasHiddenProperties()) {
       proto_with_hidden_properties++;
     }
     if (i < length - 1) {
@@ -4750,7 +4888,9 @@
         return isolate->heap()->boolean_symbol();
       }
       if (heap_obj->IsNull()) {
-        return isolate->heap()->object_symbol();
+        return FLAG_harmony_typeof
+            ? isolate->heap()->null_symbol()
+            : isolate->heap()->object_symbol();
       }
       ASSERT(heap_obj->IsUndefined());
       return isolate->heap()->undefined_symbol();
@@ -5311,12 +5451,14 @@
     str = String::cast(flat);
     ASSERT(str->IsFlat());
   }
-  if (str->IsTwoByteRepresentation()) {
+  String::FlatContent flat = str->GetFlatContent();
+  ASSERT(flat.IsFlat());
+  if (flat.IsTwoByte()) {
     return QuoteJsonString<uc16, SeqTwoByteString, false>(isolate,
-                                                          str->ToUC16Vector());
+                                                          flat.ToUC16Vector());
   } else {
     return QuoteJsonString<char, SeqAsciiString, false>(isolate,
-                                                        str->ToAsciiVector());
+                                                        flat.ToAsciiVector());
   }
 }
 
@@ -5333,12 +5475,13 @@
     str = String::cast(flat);
     ASSERT(str->IsFlat());
   }
-  if (str->IsTwoByteRepresentation()) {
+  String::FlatContent flat = str->GetFlatContent();
+  if (flat.IsTwoByte()) {
     return QuoteJsonString<uc16, SeqTwoByteString, true>(isolate,
-                                                         str->ToUC16Vector());
+                                                         flat.ToUC16Vector());
   } else {
     return QuoteJsonString<char, SeqAsciiString, true>(isolate,
-                                                       str->ToAsciiVector());
+                                                       flat.ToAsciiVector());
   }
 }
 
@@ -5373,14 +5516,16 @@
   for (int i = 0; i < length; i++) {
     if (i != 0) *(write_cursor++) = ',';
     String* str = String::cast(array->get(i));
-    if (str->IsTwoByteRepresentation()) {
+    String::FlatContent content = str->GetFlatContent();
+    ASSERT(content.IsFlat());
+    if (content.IsTwoByte()) {
       write_cursor = WriteQuoteJsonString<Char, uc16>(isolate,
                                                       write_cursor,
-                                                      str->ToUC16Vector());
+                                                      content.ToUC16Vector());
     } else {
       write_cursor = WriteQuoteJsonString<Char, char>(isolate,
                                                       write_cursor,
-                                                      str->ToAsciiVector());
+                                                      content.ToAsciiVector());
     }
   }
   *(write_cursor++) = ']';
@@ -5859,11 +6004,15 @@
 
   // No allocation block.
   {
-    AssertNoAllocation nogc;
-    if (subject->IsAsciiRepresentation()) {
-      Vector<const char> subject_vector = subject->ToAsciiVector();
-      if (pattern->IsAsciiRepresentation()) {
-        Vector<const char> pattern_vector = pattern->ToAsciiVector();
+    AssertNoAllocation no_gc;
+    String::FlatContent subject_content = subject->GetFlatContent();
+    String::FlatContent pattern_content = pattern->GetFlatContent();
+    ASSERT(subject_content.IsFlat());
+    ASSERT(pattern_content.IsFlat());
+    if (subject_content.IsAscii()) {
+      Vector<const char> subject_vector = subject_content.ToAsciiVector();
+      if (pattern_content.IsAscii()) {
+        Vector<const char> pattern_vector = pattern_content.ToAsciiVector();
         if (pattern_vector.length() == 1) {
           FindAsciiStringIndices(subject_vector,
                                  pattern_vector[0],
@@ -5879,22 +6028,22 @@
       } else {
         FindStringIndices(isolate,
                           subject_vector,
-                          pattern->ToUC16Vector(),
+                          pattern_content.ToUC16Vector(),
                           &indices,
                           limit);
       }
     } else {
-      Vector<const uc16> subject_vector = subject->ToUC16Vector();
+      Vector<const uc16> subject_vector = subject_content.ToUC16Vector();
       if (pattern->IsAsciiRepresentation()) {
         FindStringIndices(isolate,
                           subject_vector,
-                          pattern->ToAsciiVector(),
+                          pattern_content.ToAsciiVector(),
                           &indices,
                           limit);
       } else {
         FindStringIndices(isolate,
                           subject_vector,
-                          pattern->ToUC16Vector(),
+                          pattern_content.ToUC16Vector(),
                           &indices,
                           limit);
       }
@@ -5943,7 +6092,7 @@
                                        const char* chars,
                                        FixedArray* elements,
                                        int length) {
-  AssertNoAllocation nogc;
+  AssertNoAllocation no_gc;
   FixedArray* ascii_cache = heap->single_character_string_cache();
   Object* undefined = heap->undefined_value();
   int i;
@@ -5976,36 +6125,39 @@
   CONVERT_ARG_CHECKED(String, s, 0);
   CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
 
-  s->TryFlatten();
+  s = FlattenGetString(s);
   const int length = static_cast<int>(Min<uint32_t>(s->length(), limit));
 
   Handle<FixedArray> elements;
+  int position = 0;
   if (s->IsFlat() && s->IsAsciiRepresentation()) {
+    // Try using cached chars where possible.
     Object* obj;
     { MaybeObject* maybe_obj =
           isolate->heap()->AllocateUninitializedFixedArray(length);
       if (!maybe_obj->ToObject(&obj)) return maybe_obj;
     }
     elements = Handle<FixedArray>(FixedArray::cast(obj), isolate);
-
-    Vector<const char> chars = s->ToAsciiVector();
-    // Note, this will initialize all elements (not only the prefix)
-    // to prevent GC from seeing partially initialized array.
-    int num_copied_from_cache = CopyCachedAsciiCharsToArray(isolate->heap(),
-                                                            chars.start(),
-                                                            *elements,
-                                                            length);
-
-    for (int i = num_copied_from_cache; i < length; ++i) {
-      Handle<Object> str = LookupSingleCharacterStringFromCode(chars[i]);
-      elements->set(i, *str);
+    String::FlatContent content = s->GetFlatContent();
+    if (content.IsAscii()) {
+      Vector<const char> chars = content.ToAsciiVector();
+      // Note, this will initialize all elements (not only the prefix)
+      // to prevent GC from seeing partially initialized array.
+      position = CopyCachedAsciiCharsToArray(isolate->heap(),
+                                             chars.start(),
+                                             *elements,
+                                             length);
+    } else {
+      MemsetPointer(elements->data_start(),
+                    isolate->heap()->undefined_value(),
+                    length);
     }
   } else {
     elements = isolate->factory()->NewFixedArray(length);
-    for (int i = 0; i < length; ++i) {
-      Handle<Object> str = LookupSingleCharacterStringFromCode(s->Get(i));
-      elements->set(i, *str);
-    }
+  }
+  for (int i = position; i < length; ++i) {
+    Handle<Object> str = LookupSingleCharacterStringFromCode(s->Get(i));
+    elements->set(i, *str);
   }
 
 #ifdef DEBUG
@@ -6509,7 +6661,7 @@
 
   // Find total length of join result.
   int string_length = 0;
-  bool is_ascii = true;
+  bool is_ascii = separator->IsAsciiRepresentation();
   int max_string_length = SeqAsciiString::kMaxLength;
   bool overflow = false;
   CONVERT_NUMBER_CHECKED(int, elements_length,
@@ -6816,22 +6968,24 @@
     equal_prefix_result = Smi::FromInt(LESS);
   }
   int r;
-  if (x->IsAsciiRepresentation()) {
-    Vector<const char> x_chars = x->ToAsciiVector();
-    if (y->IsAsciiRepresentation()) {
-      Vector<const char> y_chars = y->ToAsciiVector();
+  String::FlatContent x_content = x->GetFlatContent();
+  String::FlatContent y_content = y->GetFlatContent();
+  if (x_content.IsAscii()) {
+    Vector<const char> x_chars = x_content.ToAsciiVector();
+    if (y_content.IsAscii()) {
+      Vector<const char> y_chars = y_content.ToAsciiVector();
       r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
     } else {
-      Vector<const uc16> y_chars = y->ToUC16Vector();
+      Vector<const uc16> y_chars = y_content.ToUC16Vector();
       r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
     }
   } else {
-    Vector<const uc16> x_chars = x->ToUC16Vector();
-    if (y->IsAsciiRepresentation()) {
-      Vector<const char> y_chars = y->ToAsciiVector();
+    Vector<const uc16> x_chars = x_content.ToUC16Vector();
+    if (y_content.IsAscii()) {
+      Vector<const char> y_chars = y_content.ToAsciiVector();
       r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
     } else {
-      Vector<const uc16> y_chars = y->ToUC16Vector();
+      Vector<const uc16> y_chars = y_content.ToUC16Vector();
       r = CompareChars(x_chars.start(), y_chars.start(), prefix_length);
     }
   }
@@ -8211,6 +8365,30 @@
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_PushBlockContext) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 2);
+  SerializedScopeInfo* scope_info = SerializedScopeInfo::cast(args[0]);
+  JSFunction* function;
+  if (args[1]->IsSmi()) {
+    // A smi sentinel indicates a context nested inside global code rather
+    // than some function.  There is a canonical empty function that can be
+    // gotten from the global context.
+    function = isolate->context()->global_context()->closure();
+  } else {
+    function = JSFunction::cast(args[1]);
+  }
+  Context* context;
+  MaybeObject* maybe_context =
+      isolate->heap()->AllocateBlockContext(function,
+                                            isolate->context(),
+                                            scope_info);
+  if (!maybe_context->To(&context)) return maybe_context;
+  isolate->set_context(context);
+  return context;
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DeleteContextSlot) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 2);
@@ -8221,7 +8399,12 @@
   int index;
   PropertyAttributes attributes;
   ContextLookupFlags flags = FOLLOW_CHAINS;
-  Handle<Object> holder = context->Lookup(name, flags, &index, &attributes);
+  BindingFlags binding_flags;
+  Handle<Object> holder = context->Lookup(name,
+                                          flags,
+                                          &index,
+                                          &attributes,
+                                          &binding_flags);
 
   // If the slot was not found the result is true.
   if (holder.is_null()) {
@@ -8323,7 +8506,12 @@
   int index;
   PropertyAttributes attributes;
   ContextLookupFlags flags = FOLLOW_CHAINS;
-  Handle<Object> holder = context->Lookup(name, flags, &index, &attributes);
+  BindingFlags binding_flags;
+  Handle<Object> holder = context->Lookup(name,
+                                          flags,
+                                          &index,
+                                          &attributes,
+                                          &binding_flags);
 
   // If the index is non-negative, the slot has been found in a local
   // variable or a parameter. Read it from the context object or the
@@ -8339,7 +8527,17 @@
     MaybeObject* value = (holder->IsContext())
         ? Context::cast(*holder)->get(index)
         : JSObject::cast(*holder)->GetElement(index);
-    return MakePair(Unhole(isolate->heap(), value, attributes), *receiver);
+    // Check for uninitialized bindings.
+    if (holder->IsContext() &&
+        binding_flags == MUTABLE_CHECK_INITIALIZED &&
+        value->IsTheHole()) {
+      Handle<Object> reference_error =
+          isolate->factory()->NewReferenceError("not_defined",
+                                                HandleVector(&name, 1));
+      return MakePair(isolate->Throw(*reference_error), NULL);
+    } else {
+      return MakePair(Unhole(isolate->heap(), value, attributes), *receiver);
+    }
   }
 
   // If the holder is found, we read the property from it.
@@ -8405,14 +8603,27 @@
   int index;
   PropertyAttributes attributes;
   ContextLookupFlags flags = FOLLOW_CHAINS;
-  Handle<Object> holder = context->Lookup(name, flags, &index, &attributes);
+  BindingFlags binding_flags;
+  Handle<Object> holder = context->Lookup(name,
+                                          flags,
+                                          &index,
+                                          &attributes,
+                                          &binding_flags);
 
   if (index >= 0) {
     if (holder->IsContext()) {
+      Handle<Context> context = Handle<Context>::cast(holder);
+      if (binding_flags == MUTABLE_CHECK_INITIALIZED &&
+          context->get(index)->IsTheHole()) {
+        Handle<Object> error =
+            isolate->factory()->NewReferenceError("not_defined",
+                                                  HandleVector(&name, 1));
+        return isolate->Throw(*error);
+      }
       // Ignore if read_only variable.
       if ((attributes & READ_ONLY) == 0) {
         // Context is a fixed array and set cannot fail.
-        Context::cast(*holder)->set(index, *value);
+        context->set(index, *value);
       } else if (strict_mode == kStrictMode) {
         // Setting read only property in strict mode.
         Handle<Object> error =
@@ -8688,13 +8899,14 @@
   FixedArray* output_array = FixedArray::cast(output->elements());
   RUNTIME_ASSERT(output_array->length() >= DateParser::OUTPUT_SIZE);
   bool result;
-  if (str->IsAsciiRepresentation()) {
-    result = DateParser::Parse(str->ToAsciiVector(),
+  String::FlatContent str_content = str->GetFlatContent();
+  if (str_content.IsAscii()) {
+    result = DateParser::Parse(str_content.ToAsciiVector(),
                                output_array,
                                isolate->unicode_cache());
   } else {
-    ASSERT(str->IsTwoByteRepresentation());
-    result = DateParser::Parse(str->ToUC16Vector(),
+    ASSERT(str_content.IsTwoByte());
+    result = DateParser::Parse(str_content.ToUC16Vector(),
                                output_array,
                                isolate->unicode_cache());
   }
@@ -8863,10 +9075,13 @@
   // it is bound in the global context.
   int index = -1;
   PropertyAttributes attributes = ABSENT;
+  BindingFlags binding_flags;
   while (true) {
     receiver = context->Lookup(isolate->factory()->eval_symbol(),
                                FOLLOW_PROTOTYPE_CHAIN,
-                               &index, &attributes);
+                               &index,
+                               &attributes,
+                               &binding_flags);
     // Stop search when eval is found or when the global context is
     // reached.
     if (attributes != ABSENT || context->IsGlobalContext()) break;
@@ -9166,13 +9381,13 @@
     if (elements_are_guaranteed_smis) {
       for (uint32_t j = 0; j < len; j++) {
         HandleScope loop_scope;
-        Handle<Smi> e(Smi::FromInt(static_cast<int>(array->get(j))));
+        Handle<Smi> e(Smi::FromInt(static_cast<int>(array->get_scalar(j))));
         visitor->visit(j, e);
       }
     } else {
       for (uint32_t j = 0; j < len; j++) {
         HandleScope loop_scope;
-        int64_t val = static_cast<int64_t>(array->get(j));
+        int64_t val = static_cast<int64_t>(array->get_scalar(j));
         if (Smi::IsValid(static_cast<intptr_t>(val))) {
           Handle<Smi> e(Smi::FromInt(static_cast<int>(val)));
           visitor->visit(j, e);
@@ -9186,7 +9401,7 @@
   } else {
     for (uint32_t j = 0; j < len; j++) {
       HandleScope loop_scope(isolate);
-      Handle<Object> e = isolate->factory()->NewNumber(array->get(j));
+      Handle<Object> e = isolate->factory()->NewNumber(array->get_scalar(j));
       visitor->visit(j, e);
     }
   }
@@ -9372,7 +9587,7 @@
       Handle<ExternalPixelArray> pixels(ExternalPixelArray::cast(
           receiver->elements()));
       for (uint32_t j = 0; j < length; j++) {
-        Handle<Smi> e(Smi::FromInt(pixels->get(j)));
+        Handle<Smi> e(Smi::FromInt(pixels->get_scalar(j)));
         visitor->visit(j, e);
       }
       break;
@@ -9551,11 +9766,14 @@
   ASSERT(args.length() == 2);
   CONVERT_CHECKED(JSArray, from, args[0]);
   CONVERT_CHECKED(JSArray, to, args[1]);
-  HeapObject* new_elements = from->elements();
+  FixedArrayBase* new_elements = from->elements();
   MaybeObject* maybe_new_map;
   if (new_elements->map() == isolate->heap()->fixed_array_map() ||
       new_elements->map() == isolate->heap()->fixed_cow_array_map()) {
     maybe_new_map = to->map()->GetFastElementsMap();
+  } else if (new_elements->map() ==
+             isolate->heap()->fixed_double_array_map()) {
+    maybe_new_map = to->map()->GetFastDoubleElementsMap();
   } else {
     maybe_new_map = to->map()->GetSlowElementsMap();
   }
@@ -9643,12 +9861,13 @@
     }
     return *isolate->factory()->NewJSArrayWithElements(keys);
   } else {
-    ASSERT(array->HasFastElements());
+    ASSERT(array->HasFastElements() || array->HasFastDoubleElements());
     Handle<FixedArray> single_interval = isolate->factory()->NewFixedArray(2);
     // -1 means start of array.
     single_interval->set(0, Smi::FromInt(-1));
+    FixedArrayBase* elements = FixedArrayBase::cast(array->elements());
     uint32_t actual_length =
-        static_cast<uint32_t>(FixedArray::cast(array->elements())->length());
+        static_cast<uint32_t>(elements->length());
     uint32_t min_length = actual_length < length ? actual_length : length;
     Handle<Object> length_object =
         isolate->factory()->NewNumber(static_cast<double>(min_length));
@@ -10532,6 +10751,34 @@
 }
 
 
+// Create a plain JSObject which materializes the block scope for the specified
+// block context.
+static Handle<JSObject> MaterializeBlockScope(
+    Isolate* isolate,
+    Handle<Context> context) {
+  ASSERT(context->IsBlockContext());
+  Handle<SerializedScopeInfo> serialized_scope_info(
+      SerializedScopeInfo::cast(context->extension()));
+  ScopeInfo<> scope_info(*serialized_scope_info);
+
+  // Allocate and initialize a JSObject with all the arguments, stack locals
+  // heap locals and extension properties of the debugged function.
+  Handle<JSObject> block_scope =
+      isolate->factory()->NewJSObject(isolate->object_function());
+
+  // Fill all context locals.
+  if (scope_info.number_of_context_slots() > Context::MIN_CONTEXT_SLOTS) {
+    if (!CopyContextLocalsToScopeObject(isolate,
+                                        serialized_scope_info, scope_info,
+                                        context, block_scope)) {
+      return Handle<JSObject>();
+    }
+  }
+
+  return block_scope;
+}
+
+
 // Iterate over the actual scopes visible from a stack frame. All scopes are
 // backed by an actual context except the local scope, which is inserted
 // "artifically" in the context chain.
@@ -10542,7 +10789,8 @@
     ScopeTypeLocal,
     ScopeTypeWith,
     ScopeTypeClosure,
-    ScopeTypeCatch
+    ScopeTypeCatch,
+    ScopeTypeBlock
   };
 
   ScopeIterator(Isolate* isolate,
@@ -10568,8 +10816,10 @@
     } else if (context_->IsFunctionContext()) {
       at_local_ = true;
     } else if (context_->closure() != *function_) {
-      // The context_ is a with or catch block from the outer function.
-      ASSERT(context_->IsWithContext() || context_->IsCatchContext());
+      // The context_ is a block or with or catch block from the outer function.
+      ASSERT(context_->IsWithContext() ||
+             context_->IsCatchContext() ||
+             context_->IsBlockContext());
       at_local_ = true;
     }
   }
@@ -10624,6 +10874,9 @@
     if (context_->IsCatchContext()) {
       return ScopeTypeCatch;
     }
+    if (context_->IsBlockContext()) {
+      return ScopeTypeBlock;
+    }
     ASSERT(context_->IsWithContext());
     return ScopeTypeWith;
   }
@@ -10644,6 +10897,8 @@
       case ScopeIterator::ScopeTypeClosure:
         // Materialize the content of the closure scope into a JSObject.
         return MaterializeClosure(isolate_, CurrentContext());
+      case ScopeIterator::ScopeTypeBlock:
+        return MaterializeBlockScope(isolate_, CurrentContext());
     }
     UNREACHABLE();
     return Handle<JSObject>();
@@ -11200,7 +11455,18 @@
                                             new_previous,
                                             name,
                                             thrown_object);
+  } else if (current->IsBlockContext()) {
+    Handle<SerializedScopeInfo> scope_info(
+        SerializedScopeInfo::cast(current->extension()));
+    new_current =
+        isolate->factory()->NewBlockContext(function, new_previous, scope_info);
+    // Copy context slots.
+    int num_context_slots = scope_info->NumberOfContextSlots();
+    for (int i = Context::MIN_CONTEXT_SLOTS; i < num_context_slots; ++i) {
+      new_current->set(i, current->get(i));
+    }
   } else {
+    ASSERT(current->IsWithContext());
     Handle<JSObject> extension(JSObject::cast(current->extension()));
     new_current =
         isolate->factory()->NewWithContext(function, new_previous, extension);
@@ -11338,7 +11604,11 @@
   context->set_extension(*local_scope);
   // Copy any with contexts present and chain them in front of this context.
   Handle<Context> frame_context(Context::cast(frame->context()));
-  Handle<Context> function_context(frame_context->declaration_context());
+  Handle<Context> function_context;
+  // Get the function's context if it has one.
+  if (scope_info->HasHeapAllocatedLocals()) {
+    function_context = Handle<Context>(frame_context->declaration_context());
+  }
   context = CopyWithContextChain(isolate, go_between, frame_context, context);
 
   if (additional_context->IsJSObject()) {
@@ -12619,7 +12889,9 @@
   ASSERT(args.length() == 2);
   CONVERT_CHECKED(String, format, args[0]);
   CONVERT_CHECKED(JSArray, elms, args[1]);
-  Vector<const char> chars = format->ToAsciiVector();
+  String::FlatContent format_content = format->GetFlatContent();
+  RUNTIME_ASSERT(format_content.IsAscii());
+  Vector<const char> chars = format_content.ToAsciiVector();
   LOGGER->LogRuntime(chars, elms);
   return isolate->heap()->undefined_value();
 }
diff --git a/src/runtime.h b/src/runtime.h
index 9a2cf1d..91a19df 100644
--- a/src/runtime.h
+++ b/src/runtime.h
@@ -65,7 +65,7 @@
   F(ToSlowProperties, 1, 1) \
   F(FinishArrayPrototypeSetup, 1, 1) \
   F(SpecialArrayFunctions, 1, 1) \
-  F(GetGlobalReceiver, 0, 1) \
+  F(GetDefaultReceiver, 1, 1) \
   \
   F(GetPrototype, 1, 1) \
   F(IsInPrototypeChain, 2, 1) \
@@ -209,7 +209,9 @@
   /* Reflection */ \
   F(FunctionSetInstanceClassName, 2, 1) \
   F(FunctionSetLength, 2, 1) \
+  F(BoundFunctionSetLength, 2, 1)    \
   F(FunctionSetPrototype, 2, 1) \
+  F(FunctionSetReadOnlyPrototype, 1, 1) \
   F(FunctionGetName, 1, 1) \
   F(FunctionSetName, 2, 1) \
   F(FunctionNameShouldPrintAsAnonymous, 1, 1) \
@@ -288,6 +290,11 @@
   F(GetHandler, 1, 1) \
   F(Fix, 1, 1) \
   \
+  /* Harmony weakmaps */ \
+  F(WeakMapInitialize, 1, 1) \
+  F(WeakMapGet, 2, 1) \
+  F(WeakMapSet, 3, 1) \
+  \
   /* Statements */ \
   F(NewClosure, 3, 1) \
   F(NewObject, 1, 1) \
@@ -303,6 +310,7 @@
   F(NewFunctionContext, 1, 1) \
   F(PushWithContext, 2, 1) \
   F(PushCatchContext, 3, 1) \
+  F(PushBlockContext, 2, 1) \
   F(DeleteContextSlot, 2, 1) \
   F(LoadContextSlot, 2, 2) \
   F(LoadContextSlotNoReferenceError, 2, 2) \
@@ -483,8 +491,7 @@
   F(IsRegExpEquivalent, 2, 1)                                                \
   F(HasCachedArrayIndex, 1, 1)                                               \
   F(GetCachedArrayIndex, 1, 1)                                               \
-  F(FastAsciiArrayJoin, 2, 1)                                                \
-  F(IsNativeOrStrictMode, 1, 1)
+  F(FastAsciiArrayJoin, 2, 1)
 
 
 // ----------------------------------------------------------------------------
diff --git a/src/scanner-base.cc b/src/scanner-base.cc
index 16f8db5..62eee1a 100644
--- a/src/scanner-base.cc
+++ b/src/scanner-base.cc
@@ -41,12 +41,12 @@
     : unicode_cache_(unicode_cache) { }
 
 
-uc32 Scanner::ScanHexEscape(uc32 c, int length) {
-  ASSERT(length <= 4);  // prevent overflow
+uc32 Scanner::ScanHexNumber(int expected_length) {
+  ASSERT(expected_length <= 4);  // prevent overflow
 
-  uc32 digits[4];
+  uc32 digits[4] = { 0, 0, 0, 0 };
   uc32 x = 0;
-  for (int i = 0; i < length; i++) {
+  for (int i = 0; i < expected_length; i++) {
     digits[i] = c0_;
     int d = HexValue(c0_);
     if (d < 0) {
@@ -54,12 +54,11 @@
       // should be illegal, but other JS VMs just return the
       // non-escaped version of the original character.
 
-      // Push back digits read, except the last one (in c0_).
+      // Push back digits that we have advanced past.
       for (int j = i-1; j >= 0; j--) {
         PushBack(digits[j]);
       }
-      // Notice: No handling of error - treat it as "\u"->"u".
-      return c;
+      return -1;
     }
     x = x * 16 + d;
     Advance();
@@ -74,7 +73,9 @@
 // JavaScriptScanner
 
 JavaScriptScanner::JavaScriptScanner(UnicodeCache* scanner_contants)
-  : Scanner(scanner_contants), octal_pos_(Location::invalid()) { }
+    : Scanner(scanner_contants),
+      octal_pos_(Location::invalid()),
+      harmony_block_scoping_(false) { }
 
 
 void JavaScriptScanner::Initialize(UC16CharacterStream* source) {
@@ -89,10 +90,158 @@
   Scan();
 }
 
+
+// Ensure that tokens can be stored in a byte.
+STATIC_ASSERT(Token::NUM_TOKENS <= 0x100);
+
+// Table of one-character tokens, by character (0x00..0x7f only).
+static const byte one_char_tokens[] = {
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::LPAREN,       // 0x28
+  Token::RPAREN,       // 0x29
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::COMMA,        // 0x2c
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::COLON,        // 0x3a
+  Token::SEMICOLON,    // 0x3b
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::CONDITIONAL,  // 0x3f
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::LBRACK,     // 0x5b
+  Token::ILLEGAL,
+  Token::RBRACK,     // 0x5d
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::ILLEGAL,
+  Token::LBRACE,       // 0x7b
+  Token::ILLEGAL,
+  Token::RBRACE,       // 0x7d
+  Token::BIT_NOT,      // 0x7e
+  Token::ILLEGAL
+};
+
+
 Token::Value JavaScriptScanner::Next() {
   current_ = next_;
   has_line_terminator_before_next_ = false;
   has_multiline_comment_before_next_ = false;
+  if (static_cast<unsigned>(c0_) <= 0x7f) {
+    Token::Value token = static_cast<Token::Value>(one_char_tokens[c0_]);
+    if (token != Token::ILLEGAL) {
+      int pos = source_pos();
+      next_.token = token;
+      next_.location.beg_pos = pos;
+      next_.location.end_pos = pos + 1;
+      Advance();
+      return current_.token;
+    }
+  }
   Scan();
   return current_.token;
 }
@@ -171,7 +320,7 @@
   Advance();
 
   while (c0_ >= 0) {
-    char ch = c0_;
+    uc32 ch = c0_;
     Advance();
     if (unicode_cache_->IsLineTerminator(ch)) {
       // Following ECMA-262, section 7.4, a comment containing
@@ -490,9 +639,17 @@
     case 'n' : c = '\n'; break;
     case 'r' : c = '\r'; break;
     case 't' : c = '\t'; break;
-    case 'u' : c = ScanHexEscape(c, 4); break;
+    case 'u' : {
+      c = ScanHexNumber(4);
+      if (c < 0) c = 'u';
+      break;
+    }
     case 'v' : c = '\v'; break;
-    case 'x' : c = ScanHexEscape(c, 2); break;
+    case 'x' : {
+      c = ScanHexNumber(2);
+      if (c < 0) c = 'x';
+      break;
+    }
     case '0' :  // fall through
     case '1' :  // fall through
     case '2' :  // fall through
@@ -652,25 +809,133 @@
 
 uc32 JavaScriptScanner::ScanIdentifierUnicodeEscape() {
   Advance();
-  if (c0_ != 'u') return unibrow::Utf8::kBadChar;
+  if (c0_ != 'u') return -1;
   Advance();
-  uc32 c = ScanHexEscape('u', 4);
-  // We do not allow a unicode escape sequence to start another
-  // unicode escape sequence.
-  if (c == '\\') return unibrow::Utf8::kBadChar;
-  return c;
+  uc32 result = ScanHexNumber(4);
+  if (result < 0) PushBack('u');
+  return result;
+}
+
+
+// ----------------------------------------------------------------------------
+// Keyword Matcher
+
+#define KEYWORDS(KEYWORD_GROUP, KEYWORD)                            \
+  KEYWORD_GROUP('b')                                                \
+  KEYWORD("break", Token::BREAK)                                    \
+  KEYWORD_GROUP('c')                                                \
+  KEYWORD("case", Token::CASE)                                      \
+  KEYWORD("catch", Token::CATCH)                                    \
+  KEYWORD("class", Token::FUTURE_RESERVED_WORD)                     \
+  KEYWORD("const", Token::CONST)                                    \
+  KEYWORD("continue", Token::CONTINUE)                              \
+  KEYWORD_GROUP('d')                                                \
+  KEYWORD("debugger", Token::DEBUGGER)                              \
+  KEYWORD("default", Token::DEFAULT)                                \
+  KEYWORD("delete", Token::DELETE)                                  \
+  KEYWORD("do", Token::DO)                                          \
+  KEYWORD_GROUP('e')                                                \
+  KEYWORD("else", Token::ELSE)                                      \
+  KEYWORD("enum", Token::FUTURE_RESERVED_WORD)                      \
+  KEYWORD("export", Token::FUTURE_RESERVED_WORD)                    \
+  KEYWORD("extends", Token::FUTURE_RESERVED_WORD)                   \
+  KEYWORD_GROUP('f')                                                \
+  KEYWORD("false", Token::FALSE_LITERAL)                            \
+  KEYWORD("finally", Token::FINALLY)                                \
+  KEYWORD("for", Token::FOR)                                        \
+  KEYWORD("function", Token::FUNCTION)                              \
+  KEYWORD_GROUP('i')                                                \
+  KEYWORD("if", Token::IF)                                          \
+  KEYWORD("implements", Token::FUTURE_STRICT_RESERVED_WORD)         \
+  KEYWORD("import", Token::FUTURE_RESERVED_WORD)                    \
+  KEYWORD("in", Token::IN)                                          \
+  KEYWORD("instanceof", Token::INSTANCEOF)                          \
+  KEYWORD("interface", Token::FUTURE_STRICT_RESERVED_WORD)          \
+  KEYWORD_GROUP('l')                                                \
+  KEYWORD("let", harmony_block_scoping                              \
+                 ? Token::LET : Token::FUTURE_STRICT_RESERVED_WORD) \
+  KEYWORD_GROUP('n')                                                \
+  KEYWORD("new", Token::NEW)                                        \
+  KEYWORD("null", Token::NULL_LITERAL)                              \
+  KEYWORD_GROUP('p')                                                \
+  KEYWORD("package", Token::FUTURE_STRICT_RESERVED_WORD)            \
+  KEYWORD("private", Token::FUTURE_STRICT_RESERVED_WORD)            \
+  KEYWORD("protected", Token::FUTURE_STRICT_RESERVED_WORD)          \
+  KEYWORD("public", Token::FUTURE_STRICT_RESERVED_WORD)             \
+  KEYWORD_GROUP('r')                                                \
+  KEYWORD("return", Token::RETURN)                                  \
+  KEYWORD_GROUP('s')                                                \
+  KEYWORD("static", Token::FUTURE_STRICT_RESERVED_WORD)             \
+  KEYWORD("super", Token::FUTURE_RESERVED_WORD)                     \
+  KEYWORD("switch", Token::SWITCH)                                  \
+  KEYWORD_GROUP('t')                                                \
+  KEYWORD("this", Token::THIS)                                      \
+  KEYWORD("throw", Token::THROW)                                    \
+  KEYWORD("true", Token::TRUE_LITERAL)                              \
+  KEYWORD("try", Token::TRY)                                        \
+  KEYWORD("typeof", Token::TYPEOF)                                  \
+  KEYWORD_GROUP('v')                                                \
+  KEYWORD("var", Token::VAR)                                        \
+  KEYWORD("void", Token::VOID)                                      \
+  KEYWORD_GROUP('w')                                                \
+  KEYWORD("while", Token::WHILE)                                    \
+  KEYWORD("with", Token::WITH)                                      \
+  KEYWORD_GROUP('y')                                                \
+  KEYWORD("yield", Token::FUTURE_STRICT_RESERVED_WORD)
+
+
+static Token::Value KeywordOrIdentifierToken(const char* input,
+                                             int input_length,
+                                             bool harmony_block_scoping) {
+  ASSERT(input_length >= 1);
+  const int kMinLength = 2;
+  const int kMaxLength = 10;
+  if (input_length < kMinLength || input_length > kMaxLength) {
+    return Token::IDENTIFIER;
+  }
+  switch (input[0]) {
+    default:
+#define KEYWORD_GROUP_CASE(ch)                                \
+      break;                                                  \
+    case ch:
+#define KEYWORD(keyword, token)                               \
+    {                                                         \
+      /* 'keyword' is a char array, so sizeof(keyword) is */  \
+      /* strlen(keyword) plus 1 for the NUL char. */          \
+      const int keyword_length = sizeof(keyword) - 1;         \
+      STATIC_ASSERT(keyword_length >= kMinLength);            \
+      STATIC_ASSERT(keyword_length <= kMaxLength);            \
+      if (input_length == keyword_length &&                   \
+          input[1] == keyword[1] &&                           \
+          (keyword_length <= 2 || input[2] == keyword[2]) &&  \
+          (keyword_length <= 3 || input[3] == keyword[3]) &&  \
+          (keyword_length <= 4 || input[4] == keyword[4]) &&  \
+          (keyword_length <= 5 || input[5] == keyword[5]) &&  \
+          (keyword_length <= 6 || input[6] == keyword[6]) &&  \
+          (keyword_length <= 7 || input[7] == keyword[7]) &&  \
+          (keyword_length <= 8 || input[8] == keyword[8]) &&  \
+          (keyword_length <= 9 || input[9] == keyword[9])) {  \
+        return token;                                         \
+      }                                                       \
+    }
+    KEYWORDS(KEYWORD_GROUP_CASE, KEYWORD)
+  }
+  return Token::IDENTIFIER;
 }
 
 
 Token::Value JavaScriptScanner::ScanIdentifierOrKeyword() {
   ASSERT(unicode_cache_->IsIdentifierStart(c0_));
   LiteralScope literal(this);
-  KeywordMatcher keyword_match;
   // Scan identifier start character.
   if (c0_ == '\\') {
     uc32 c = ScanIdentifierUnicodeEscape();
     // Only allow legal identifier start characters.
-    if (!unicode_cache_->IsIdentifierStart(c)) return Token::ILLEGAL;
+    if (c < 0 ||
+        c == '\\' ||  // No recursive escapes.
+        !unicode_cache_->IsIdentifierStart(c)) {
+      return Token::ILLEGAL;
+    }
     AddLiteralChar(c);
     return ScanIdentifierSuffix(&literal);
   }
@@ -678,9 +943,6 @@
   uc32 first_char = c0_;
   Advance();
   AddLiteralChar(first_char);
-  if (!keyword_match.AddChar(first_char)) {
-    return ScanIdentifierSuffix(&literal);
-  }
 
   // Scan the rest of the identifier characters.
   while (unicode_cache_->IsIdentifierPart(c0_)) {
@@ -688,14 +950,22 @@
       uc32 next_char = c0_;
       Advance();
       AddLiteralChar(next_char);
-      if (keyword_match.AddChar(next_char)) continue;
+      continue;
     }
-    // Fallthrough if no loner able to complete keyword.
+    // Fallthrough if no longer able to complete keyword.
     return ScanIdentifierSuffix(&literal);
   }
+
   literal.Complete();
 
-  return keyword_match.token();
+  if (next_.literal_chars->is_ascii()) {
+    Vector<const char> chars = next_.literal_chars->ascii_literal();
+    return KeywordOrIdentifierToken(chars.start(),
+                                    chars.length(),
+                                    harmony_block_scoping_);
+  }
+
+  return Token::IDENTIFIER;
 }
 
 
@@ -705,7 +975,11 @@
     if (c0_ == '\\') {
       uc32 c = ScanIdentifierUnicodeEscape();
       // Only allow legal identifier part characters.
-      if (!unicode_cache_->IsIdentifierPart(c)) return Token::ILLEGAL;
+      if (c < 0 ||
+          c == '\\' ||
+          !unicode_cache_->IsIdentifierPart(c)) {
+        return Token::ILLEGAL;
+      }
       AddLiteralChar(c);
     } else {
       AddLiteralChar(c0_);
@@ -731,8 +1005,9 @@
   // the scanner should pass uninterpreted bodies to the RegExp
   // constructor.
   LiteralScope literal(this);
-  if (seen_equal)
+  if (seen_equal) {
     AddLiteralChar('=');
+  }
 
   while (c0_ != '/' || in_character_class) {
     if (unicode_cache_->IsLineTerminator(c0_) || c0_ < 0) return false;
@@ -764,20 +1039,47 @@
 }
 
 
+bool JavaScriptScanner::ScanLiteralUnicodeEscape() {
+  ASSERT(c0_ == '\\');
+  uc32 chars_read[6] = {'\\', 'u', 0, 0, 0, 0};
+  Advance();
+  int i = 1;
+  if (c0_ == 'u') {
+    i++;
+    while (i < 6) {
+      Advance();
+      if (!IsHexDigit(c0_)) break;
+      chars_read[i] = c0_;
+      i++;
+    }
+  }
+  if (i < 6) {
+    // Incomplete escape. Undo all advances and return false.
+    while (i > 0) {
+      i--;
+      PushBack(chars_read[i]);
+    }
+    return false;
+  }
+  // Complete escape. Add all chars to current literal buffer.
+  for (int i = 0; i < 6; i++) {
+    AddLiteralChar(chars_read[i]);
+  }
+  return true;
+}
+
+
 bool JavaScriptScanner::ScanRegExpFlags() {
   // Scan regular expression flags.
   LiteralScope literal(this);
   while (unicode_cache_->IsIdentifierPart(c0_)) {
-    if (c0_ == '\\') {
-      uc32 c = ScanIdentifierUnicodeEscape();
-      if (c != static_cast<uc32>(unibrow::Utf8::kBadChar)) {
-        // We allow any escaped character, unlike the restriction on
-        // IdentifierPart when it is used to build an IdentifierName.
-        AddLiteralChar(c);
-        continue;
+    if (c0_ != '\\') {
+      AddLiteralCharAdvance();
+    } else {
+      if (!ScanLiteralUnicodeEscape()) {
+        break;
       }
     }
-    AddLiteralCharAdvance();
   }
   literal.Complete();
 
@@ -785,182 +1087,4 @@
   return true;
 }
 
-// ----------------------------------------------------------------------------
-// Keyword Matcher
-
-KeywordMatcher::FirstState KeywordMatcher::first_states_[] = {
-  { "break",  KEYWORD_PREFIX, Token::BREAK },
-  { NULL,     C,              Token::ILLEGAL },
-  { NULL,     D,              Token::ILLEGAL },
-  { NULL,     E,              Token::ILLEGAL },
-  { NULL,     F,              Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { NULL,     I,              Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { "let",    KEYWORD_PREFIX, Token::FUTURE_STRICT_RESERVED_WORD },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { NULL,     N,              Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { NULL,     P,              Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { "return", KEYWORD_PREFIX, Token::RETURN },
-  { NULL,     S,              Token::ILLEGAL },
-  { NULL,     T,              Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { NULL,     V,              Token::ILLEGAL },
-  { NULL,     W,              Token::ILLEGAL },
-  { NULL,     UNMATCHABLE,    Token::ILLEGAL },
-  { "yield",  KEYWORD_PREFIX, Token::FUTURE_STRICT_RESERVED_WORD }
-};
-
-
-void KeywordMatcher::Step(unibrow::uchar input) {
-  switch (state_) {
-    case INITIAL: {
-      // matching the first character is the only state with significant fanout.
-      // Match only lower-case letters in range 'b'..'y'.
-      unsigned int offset = input - kFirstCharRangeMin;
-      if (offset < kFirstCharRangeLength) {
-        state_ = first_states_[offset].state;
-        if (state_ == KEYWORD_PREFIX) {
-          keyword_ = first_states_[offset].keyword;
-          counter_ = 1;
-          keyword_token_ = first_states_[offset].token;
-        }
-        return;
-      }
-      break;
-    }
-    case KEYWORD_PREFIX:
-      if (static_cast<unibrow::uchar>(keyword_[counter_]) == input) {
-        counter_++;
-        if (keyword_[counter_] == '\0') {
-          state_ = KEYWORD_MATCHED;
-          token_ = keyword_token_;
-        }
-        return;
-      }
-      break;
-    case KEYWORD_MATCHED:
-      token_ = Token::IDENTIFIER;
-      break;
-    case C:
-      if (MatchState(input, 'a', CA)) return;
-      if (MatchKeywordStart(input, "class", 1,
-                            Token::FUTURE_RESERVED_WORD)) return;
-      if (MatchState(input, 'o', CO)) return;
-      break;
-    case CA:
-      if (MatchKeywordStart(input, "case", 2, Token::CASE)) return;
-      if (MatchKeywordStart(input, "catch", 2, Token::CATCH)) return;
-      break;
-    case CO:
-      if (MatchState(input, 'n', CON)) return;
-      break;
-    case CON:
-      if (MatchKeywordStart(input, "const", 3, Token::CONST)) return;
-      if (MatchKeywordStart(input, "continue", 3, Token::CONTINUE)) return;
-      break;
-    case D:
-      if (MatchState(input, 'e', DE)) return;
-      if (MatchKeyword(input, 'o', KEYWORD_MATCHED, Token::DO)) return;
-      break;
-    case DE:
-      if (MatchKeywordStart(input, "debugger", 2, Token::DEBUGGER)) return;
-      if (MatchKeywordStart(input, "default", 2, Token::DEFAULT)) return;
-      if (MatchKeywordStart(input, "delete", 2, Token::DELETE)) return;
-      break;
-    case E:
-      if (MatchKeywordStart(input, "else", 1, Token::ELSE)) return;
-      if (MatchKeywordStart(input, "enum", 1,
-                            Token::FUTURE_RESERVED_WORD)) return;
-      if (MatchState(input, 'x', EX)) return;
-      break;
-    case EX:
-      if (MatchKeywordStart(input, "export", 2,
-                            Token::FUTURE_RESERVED_WORD)) return;
-      if (MatchKeywordStart(input, "extends", 2,
-                            Token::FUTURE_RESERVED_WORD)) return;
-      break;
-    case F:
-      if (MatchKeywordStart(input, "false", 1, Token::FALSE_LITERAL)) return;
-      if (MatchKeywordStart(input, "finally", 1, Token::FINALLY)) return;
-      if (MatchKeywordStart(input, "for", 1, Token::FOR)) return;
-      if (MatchKeywordStart(input, "function", 1, Token::FUNCTION)) return;
-      break;
-    case I:
-      if (MatchKeyword(input, 'f', KEYWORD_MATCHED, Token::IF)) return;
-      if (MatchState(input, 'm', IM)) return;
-      if (MatchKeyword(input, 'n', IN, Token::IN)) return;
-      break;
-    case IM:
-      if (MatchState(input, 'p', IMP)) return;
-      break;
-    case IMP:
-      if (MatchKeywordStart(input, "implements", 3,
-                            Token::FUTURE_STRICT_RESERVED_WORD )) return;
-      if (MatchKeywordStart(input, "import", 3,
-                            Token::FUTURE_RESERVED_WORD)) return;
-      break;
-    case IN:
-      token_ = Token::IDENTIFIER;
-      if (MatchKeywordStart(input, "interface", 2,
-                            Token::FUTURE_STRICT_RESERVED_WORD)) return;
-      if (MatchKeywordStart(input, "instanceof", 2, Token::INSTANCEOF)) return;
-      break;
-    case N:
-      if (MatchKeywordStart(input, "new", 1, Token::NEW)) return;
-      if (MatchKeywordStart(input, "null", 1, Token::NULL_LITERAL)) return;
-      break;
-    case P:
-      if (MatchKeywordStart(input, "package", 1,
-                            Token::FUTURE_STRICT_RESERVED_WORD)) return;
-      if (MatchState(input, 'r', PR)) return;
-      if (MatchKeywordStart(input, "public", 1,
-                            Token::FUTURE_STRICT_RESERVED_WORD)) return;
-      break;
-    case PR:
-      if (MatchKeywordStart(input, "private", 2,
-                            Token::FUTURE_STRICT_RESERVED_WORD)) return;
-      if (MatchKeywordStart(input, "protected", 2,
-                            Token::FUTURE_STRICT_RESERVED_WORD)) return;
-      break;
-    case S:
-      if (MatchKeywordStart(input, "static", 1,
-                            Token::FUTURE_STRICT_RESERVED_WORD)) return;
-      if (MatchKeywordStart(input, "super", 1,
-                            Token::FUTURE_RESERVED_WORD)) return;
-      if (MatchKeywordStart(input, "switch", 1,
-                            Token::SWITCH)) return;
-      break;
-    case T:
-      if (MatchState(input, 'h', TH)) return;
-      if (MatchState(input, 'r', TR)) return;
-      if (MatchKeywordStart(input, "typeof", 1, Token::TYPEOF)) return;
-      break;
-    case TH:
-      if (MatchKeywordStart(input, "this", 2, Token::THIS)) return;
-      if (MatchKeywordStart(input, "throw", 2, Token::THROW)) return;
-      break;
-    case TR:
-      if (MatchKeywordStart(input, "true", 2, Token::TRUE_LITERAL)) return;
-      if (MatchKeyword(input, 'y', KEYWORD_MATCHED, Token::TRY)) return;
-      break;
-    case V:
-      if (MatchKeywordStart(input, "var", 1, Token::VAR)) return;
-      if (MatchKeywordStart(input, "void", 1, Token::VOID)) return;
-      break;
-    case W:
-      if (MatchKeywordStart(input, "while", 1, Token::WHILE)) return;
-      if (MatchKeywordStart(input, "with", 1, Token::WITH)) return;
-      break;
-    case UNMATCHABLE:
-      break;
-  }
-  // On fallthrough, it's a failure.
-  state_ = UNMATCHABLE;
-}
-
 } }  // namespace v8::internal
diff --git a/src/scanner-base.h b/src/scanner-base.h
index 3d67d4e..d68d240 100644
--- a/src/scanner-base.h
+++ b/src/scanner-base.h
@@ -362,7 +362,7 @@
   // Call this after setting source_ to the input.
   void Init() {
     // Set c0_ (one character ahead)
-    ASSERT(kCharacterLookaheadBufferSize == 1);
+    STATIC_ASSERT(kCharacterLookaheadBufferSize == 1);
     Advance();
     // Initialize current_ to not refer to a literal.
     current_.literal_chars = NULL;
@@ -419,7 +419,7 @@
     }
   }
 
-  uc32 ScanHexEscape(uc32 c, int length);
+  uc32 ScanHexNumber(int expected_length);
 
   // Return the current source position.
   int source_pos() {
@@ -507,6 +507,14 @@
   // tokens, which is what it is used for.
   void SeekForward(int pos);
 
+  bool HarmonyBlockScoping() const {
+    return harmony_block_scoping_;
+  }
+  void SetHarmonyBlockScoping(bool block_scoping) {
+    harmony_block_scoping_ = block_scoping;
+  }
+
+
  protected:
   bool SkipWhiteSpace();
   Token::Value SkipSingleLineComment();
@@ -529,6 +537,10 @@
   // Decodes a unicode escape-sequence which is part of an identifier.
   // If the escape sequence cannot be decoded the result is kBadChar.
   uc32 ScanIdentifierUnicodeEscape();
+  // Recognizes a uniocde escape-sequence and adds its characters,
+  // uninterpreted, to the current literal. Used for parsing RegExp
+  // flags.
+  bool ScanLiteralUnicodeEscape();
 
   // Start position of the octal literal last scanned.
   Location octal_pos_;
@@ -540,153 +552,11 @@
   // Whether there is a multi-line comment that contains a
   // line-terminator after the current token, and before the next.
   bool has_multiline_comment_before_next_;
+  // Whether we scan 'let' as a keyword for harmony block scoped
+  // let bindings.
+  bool harmony_block_scoping_;
 };
 
-
-// ----------------------------------------------------------------------------
-// Keyword matching state machine.
-
-class KeywordMatcher {
-//  Incrementally recognize keywords.
-//
-//  We distinguish between normal future reserved words and words that are
-//  considered to be future reserved words only in strict mode as required by
-//  ECMA-262 7.6.1.2.
-//
-//  Recognized as keywords:
-//      break, case, catch, const*, continue, debugger, default, delete, do,
-//      else, finally, false, for, function, if, in, instanceof, new, null,
-//      return, switch, this, throw, true, try, typeof, var, void, while, with.
-//
-//  Recognized as Future Reserved Keywords:
-//      class, enum, export, extends, import, super.
-//
-//  Recognized as Future Reserved Keywords (strict mode only):
-//      implements, interface, let, package, private, protected, public,
-//      static, yield.
-//
-//  *: Actually a "future reserved keyword". It's the only one we are
-//     recognizing outside of ES5 strict mode, the remaining are allowed
-//     as identifiers.
-//
- public:
-  KeywordMatcher()
-      : state_(INITIAL),
-        token_(Token::IDENTIFIER),
-        keyword_(NULL),
-        counter_(0),
-        keyword_token_(Token::ILLEGAL) {}
-
-  Token::Value token() { return token_; }
-
-  inline bool AddChar(unibrow::uchar input) {
-    if (state_ != UNMATCHABLE) {
-      Step(input);
-    }
-    return state_ != UNMATCHABLE;
-  }
-
-  void Fail() {
-    token_ = Token::IDENTIFIER;
-    state_ = UNMATCHABLE;
-  }
-
- private:
-  enum State {
-    UNMATCHABLE,
-    INITIAL,
-    KEYWORD_PREFIX,
-    KEYWORD_MATCHED,
-    C,
-    CA,
-    CO,
-    CON,
-    D,
-    DE,
-    E,
-    EX,
-    F,
-    I,
-    IM,
-    IMP,
-    IN,
-    N,
-    P,
-    PR,
-    S,
-    T,
-    TH,
-    TR,
-    V,
-    W
-  };
-
-  struct FirstState {
-    const char* keyword;
-    State state;
-    Token::Value token;
-  };
-
-  // Range of possible first characters of a keyword.
-  static const unsigned int kFirstCharRangeMin = 'b';
-  static const unsigned int kFirstCharRangeMax = 'y';
-  static const unsigned int kFirstCharRangeLength =
-      kFirstCharRangeMax - kFirstCharRangeMin + 1;
-  // State map for first keyword character range.
-  static FirstState first_states_[kFirstCharRangeLength];
-
-  // If input equals keyword's character at position, continue matching keyword
-  // from that position.
-  inline bool MatchKeywordStart(unibrow::uchar input,
-                                const char* keyword,
-                                int position,
-                                Token::Value token_if_match) {
-    if (input != static_cast<unibrow::uchar>(keyword[position])) {
-      return false;
-    }
-    state_ = KEYWORD_PREFIX;
-    this->keyword_ = keyword;
-    this->counter_ = position + 1;
-    this->keyword_token_ = token_if_match;
-    return true;
-  }
-
-  // If input equals match character, transition to new state and return true.
-  inline bool MatchState(unibrow::uchar input, char match, State new_state) {
-    if (input != static_cast<unibrow::uchar>(match)) {
-      return false;
-    }
-    state_ = new_state;
-    return true;
-  }
-
-  inline bool MatchKeyword(unibrow::uchar input,
-                           char match,
-                           State new_state,
-                           Token::Value keyword_token) {
-    if (input != static_cast<unibrow::uchar>(match)) {
-      return false;
-    }
-    state_ = new_state;
-    token_ = keyword_token;
-    return true;
-  }
-
-  void Step(unibrow::uchar input);
-
-  // Current state.
-  State state_;
-  // Token for currently added characters.
-  Token::Value token_;
-
-  // Matching a specific keyword string (there is only one possible valid
-  // keyword with the current prefix).
-  const char* keyword_;
-  int counter_;
-  Token::Value keyword_token_;
-};
-
-
 } }  // namespace v8::internal
 
 #endif  // V8_SCANNER_BASE_H_
diff --git a/src/scanner.cc b/src/scanner.cc
old mode 100755
new mode 100644
diff --git a/src/scopeinfo.cc b/src/scopeinfo.cc
index 3e18368..0eacc83 100644
--- a/src/scopeinfo.cc
+++ b/src/scopeinfo.cc
@@ -313,7 +313,7 @@
                stack_slots_.length();
 
   Handle<SerializedScopeInfo> data(
-      SerializedScopeInfo::cast(*FACTORY->NewFixedArray(length, TENURED)));
+      SerializedScopeInfo::cast(*FACTORY->NewSerializedScopeInfo(length)));
   AssertNoAllocation nogc;
 
   Object** p0 = data->data_start();
diff --git a/src/scopeinfo.h b/src/scopeinfo.h
index 86c33f6..1c61f11 100644
--- a/src/scopeinfo.h
+++ b/src/scopeinfo.h
@@ -107,7 +107,7 @@
  public :
 
   static SerializedScopeInfo* cast(Object* object) {
-    ASSERT(object->IsFixedArray());
+    ASSERT(object->IsSerializedScopeInfo());
     return reinterpret_cast<SerializedScopeInfo*>(object);
   }
 
diff --git a/src/scopes.cc b/src/scopes.cc
index 390a0b6..a76492e 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -146,7 +146,9 @@
 }
 
 
-Scope::Scope(Scope* inner_scope, Handle<SerializedScopeInfo> scope_info)
+Scope::Scope(Scope* inner_scope,
+             Type type,
+             Handle<SerializedScopeInfo> scope_info)
     : isolate_(Isolate::Current()),
       inner_scopes_(4),
       variables_(),
@@ -156,7 +158,7 @@
       decls_(4),
       already_resolved_(true) {
   ASSERT(!scope_info.is_null());
-  SetDefaults(FUNCTION_SCOPE, NULL, scope_info);
+  SetDefaults(type, NULL, scope_info);
   if (scope_info->HasHeapAllocatedLocals()) {
     num_heap_slots_ = scope_info_->NumberOfContextSlots();
   }
@@ -232,8 +234,13 @@
       if (context->IsFunctionContext()) {
         SerializedScopeInfo* scope_info =
             context->closure()->shared()->scope_info();
-        current_scope =
-            new Scope(current_scope, Handle<SerializedScopeInfo>(scope_info));
+        current_scope = new Scope(current_scope, FUNCTION_SCOPE,
+            Handle<SerializedScopeInfo>(scope_info));
+      } else if (context->IsBlockContext()) {
+        SerializedScopeInfo* scope_info =
+            SerializedScopeInfo::cast(context->extension());
+        current_scope = new Scope(current_scope, BLOCK_SCOPE,
+            Handle<SerializedScopeInfo>(scope_info));
       } else {
         ASSERT(context->IsCatchContext());
         String* name = String::cast(context->extension());
@@ -294,10 +301,13 @@
   // instead load them directly from the stack. Currently, the only
   // such parameter is 'this' which is passed on the stack when
   // invoking scripts
-  if (is_catch_scope()) {
+  if (is_catch_scope() || is_block_scope()) {
     ASSERT(outer_scope() != NULL);
     receiver_ = outer_scope()->receiver();
   } else {
+    ASSERT(is_function_scope() ||
+           is_global_scope() ||
+           is_eval_scope());
     Variable* var =
         variables_.Declare(this,
                            isolate_->factory()->this_symbol(),
@@ -387,7 +397,9 @@
   // This function handles VAR and CONST modes.  DYNAMIC variables are
   // introduces during variable allocation, INTERNAL variables are allocated
   // explicitly, and TEMPORARY variables are allocated via NewTemporary().
-  ASSERT(mode == Variable::VAR || mode == Variable::CONST);
+  ASSERT(mode == Variable::VAR ||
+         mode == Variable::CONST ||
+         mode == Variable::LET);
   ++num_var_or_const_;
   return variables_.Declare(this, name, mode, true, Variable::NORMAL);
 }
@@ -559,13 +571,22 @@
 
 Scope* Scope::DeclarationScope() {
   Scope* scope = this;
-  while (scope->is_catch_scope()) {
+  while (scope->is_catch_scope() ||
+         scope->is_block_scope()) {
     scope = scope->outer_scope();
   }
   return scope;
 }
 
 
+Handle<SerializedScopeInfo> Scope::GetSerializedScopeInfo() {
+  if (scope_info_.is_null()) {
+    scope_info_ = SerializedScopeInfo::Create(this);
+  }
+  return scope_info_;
+}
+
+
 #ifdef DEBUG
 static const char* Header(Scope::Type type) {
   switch (type) {
@@ -573,6 +594,7 @@
     case Scope::FUNCTION_SCOPE: return "function";
     case Scope::GLOBAL_SCOPE: return "global";
     case Scope::CATCH_SCOPE: return "catch";
+    case Scope::BLOCK_SCOPE: return "block";
   }
   UNREACHABLE();
   return NULL;
@@ -600,7 +622,9 @@
       PrintF("%s, ", printer->Print(var->rewrite()));
       if (var->is_accessed_from_inner_scope()) PrintF(", ");
     }
-    if (var->is_accessed_from_inner_scope()) PrintF("inner scope access");
+    if (var->is_accessed_from_inner_scope()) {
+      PrintF("inner scope access");
+    }
     PrintF("\n");
   }
 }
@@ -721,7 +745,7 @@
 // another variable that is introduced dynamically via an 'eval' call
 // or a 'with' statement).
 Variable* Scope::LookupRecursive(Handle<String> name,
-                                 bool inner_lookup,
+                                 bool from_inner_scope,
                                  Variable** invalidated_local) {
   // If we find a variable, but the current scope calls 'eval', the found
   // variable may not be the correct one (the 'eval' may introduce a
@@ -737,7 +761,7 @@
     // (Even if there is an 'eval' in this scope which introduces the
     // same variable again, the resulting variable remains the same.
     // Note that enclosing 'with' statements are handled at the call site.)
-    if (!inner_lookup)
+    if (!from_inner_scope)
       return var;
 
   } else {
@@ -770,7 +794,7 @@
   ASSERT(var != NULL);
 
   // If this is a lookup from an inner scope, mark the variable.
-  if (inner_lookup) {
+  if (from_inner_scope) {
     var->MarkAsAccessedFromInnerScope();
   }
 
@@ -926,7 +950,8 @@
        scope_calls_eval_ ||
        inner_scope_calls_eval_ ||
        scope_contains_with_ ||
-       is_catch_scope())) {
+       is_catch_scope() ||
+       is_block_scope())) {
     var->set_is_used(true);
   }
   // Global variables do not need to be allocated.
@@ -943,7 +968,7 @@
   // Exceptions: temporary variables are never allocated in a context;
   // catch-bound variables are always allocated in a context.
   if (var->mode() == Variable::TEMPORARY) return false;
-  if (is_catch_scope()) return true;
+  if (is_catch_scope() || is_block_scope()) return true;
   return var->is_accessed_from_inner_scope() ||
       scope_calls_eval_ ||
       inner_scope_calls_eval_ ||
diff --git a/src/scopes.h b/src/scopes.h
index e76fb50..c2c4179 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -93,7 +93,8 @@
     EVAL_SCOPE,      // The top-level scope for an eval source.
     FUNCTION_SCOPE,  // The top-level scope for a function.
     GLOBAL_SCOPE,    // The top-level scope for a program or a top-level eval.
-    CATCH_SCOPE      // The scope introduced by catch.
+    CATCH_SCOPE,     // The scope introduced by catch.
+    BLOCK_SCOPE      // The scope introduced by a new block.
   };
 
   Scope(Scope* outer_scope, Type type);
@@ -204,6 +205,7 @@
   bool is_function_scope() const { return type_ == FUNCTION_SCOPE; }
   bool is_global_scope() const { return type_ == GLOBAL_SCOPE; }
   bool is_catch_scope() const { return type_ == CATCH_SCOPE; }
+  bool is_block_scope() const { return type_ == BLOCK_SCOPE; }
   bool is_strict_mode() const { return strict_mode_; }
   bool is_strict_mode_eval_scope() const {
     return is_eval_scope() && is_strict_mode();
@@ -294,6 +296,8 @@
   // where var declarations will be hoisted to in the implementation.
   Scope* DeclarationScope();
 
+  Handle<SerializedScopeInfo> GetSerializedScopeInfo();
+
   // ---------------------------------------------------------------------------
   // Strict mode support.
   bool IsDeclared(Handle<String> name) {
@@ -357,11 +361,17 @@
   // Illegal redeclaration.
   Expression* illegal_redecl_;
 
-  // Scope-specific information.
-  bool scope_inside_with_;  // this scope is inside a 'with' of some outer scope
-  bool scope_contains_with_;  // this scope contains a 'with' statement
-  bool scope_calls_eval_;  // this scope contains an 'eval' call
-  bool strict_mode_;  // this scope is a strict mode scope
+  // Scope-specific information computed during parsing.
+  //
+  // This scope is inside a 'with' of some outer scope.
+  bool scope_inside_with_;
+  // This scope contains a 'with' statement.
+  bool scope_contains_with_;
+  // This scope or a nested catch scope or with scope contain an 'eval' call. At
+  // the 'eval' call site this scope is the declaration scope.
+  bool scope_calls_eval_;
+  // This scope is a strict mode scope.
+  bool strict_mode_;
 
   // Computed via PropagateScopeInfo.
   bool outer_scope_calls_eval_;
@@ -391,7 +401,7 @@
 
   // Variable resolution.
   Variable* LookupRecursive(Handle<String> name,
-                            bool inner_lookup,
+                            bool from_inner_function,
                             Variable** invalidated_local);
   void ResolveVariable(Scope* global_scope,
                        Handle<Context> context,
@@ -419,8 +429,8 @@
   void AllocateVariablesRecursively();
 
  private:
-  // Construct a function scope based on the scope info.
-  Scope(Scope* inner_scope, Handle<SerializedScopeInfo> scope_info);
+  // Construct a function or block scope based on the scope info.
+  Scope(Scope* inner_scope, Type type, Handle<SerializedScopeInfo> scope_info);
 
   // Construct a catch scope with a binding for the name.
   Scope(Scope* inner_scope, Handle<String> catch_variable_name);
diff --git a/src/serialize.cc b/src/serialize.cc
index 8cde580..094ad20 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -62,57 +62,15 @@
 }
 
 
-// ExternalReferenceTable is a helper class that defines the relationship
-// between external references and their encodings. It is used to build
-// hashmaps in ExternalReferenceEncoder and ExternalReferenceDecoder.
-class ExternalReferenceTable {
- public:
-  static ExternalReferenceTable* instance(Isolate* isolate) {
-    ExternalReferenceTable* external_reference_table =
-        isolate->external_reference_table();
-    if (external_reference_table == NULL) {
-      external_reference_table = new ExternalReferenceTable(isolate);
-      isolate->set_external_reference_table(external_reference_table);
-    }
-    return external_reference_table;
+ExternalReferenceTable* ExternalReferenceTable::instance(Isolate* isolate) {
+  ExternalReferenceTable* external_reference_table =
+      isolate->external_reference_table();
+  if (external_reference_table == NULL) {
+    external_reference_table = new ExternalReferenceTable(isolate);
+    isolate->set_external_reference_table(external_reference_table);
   }
-
-  int size() const { return refs_.length(); }
-
-  Address address(int i) { return refs_[i].address; }
-
-  uint32_t code(int i) { return refs_[i].code; }
-
-  const char* name(int i) { return refs_[i].name; }
-
-  int max_id(int code) { return max_id_[code]; }
-
- private:
-  explicit ExternalReferenceTable(Isolate* isolate) : refs_(64) {
-      PopulateTable(isolate);
-  }
-  ~ExternalReferenceTable() { }
-
-  struct ExternalReferenceEntry {
-    Address address;
-    uint32_t code;
-    const char* name;
-  };
-
-  void PopulateTable(Isolate* isolate);
-
-  // For a few types of references, we can get their address from their id.
-  void AddFromId(TypeCode type,
-                 uint16_t id,
-                 const char* name,
-                 Isolate* isolate);
-
-  // For other types of references, the caller will figure out the address.
-  void Add(Address address, TypeCode type, uint16_t id, const char* name);
-
-  List<ExternalReferenceEntry> refs_;
-  int max_id_[kTypeCodeCount];
-};
+  return external_reference_table;
+}
 
 
 void ExternalReferenceTable::AddFromId(TypeCode type,
diff --git a/src/serialize.h b/src/serialize.h
index d83722d..66d6fb5 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -60,6 +60,52 @@
 const int kDebugIdShift = kDebugRegisterBits;
 
 
+// ExternalReferenceTable is a helper class that defines the relationship
+// between external references and their encodings. It is used to build
+// hashmaps in ExternalReferenceEncoder and ExternalReferenceDecoder.
+class ExternalReferenceTable {
+ public:
+  static ExternalReferenceTable* instance(Isolate* isolate);
+
+  ~ExternalReferenceTable() { }
+
+  int size() const { return refs_.length(); }
+
+  Address address(int i) { return refs_[i].address; }
+
+  uint32_t code(int i) { return refs_[i].code; }
+
+  const char* name(int i) { return refs_[i].name; }
+
+  int max_id(int code) { return max_id_[code]; }
+
+ private:
+  explicit ExternalReferenceTable(Isolate* isolate) : refs_(64) {
+      PopulateTable(isolate);
+  }
+
+  struct ExternalReferenceEntry {
+    Address address;
+    uint32_t code;
+    const char* name;
+  };
+
+  void PopulateTable(Isolate* isolate);
+
+  // For a few types of references, we can get their address from their id.
+  void AddFromId(TypeCode type,
+                 uint16_t id,
+                 const char* name,
+                 Isolate* isolate);
+
+  // For other types of references, the caller will figure out the address.
+  void Add(Address address, TypeCode type, uint16_t id, const char* name);
+
+  List<ExternalReferenceEntry> refs_;
+  int max_id_[kTypeCodeCount];
+};
+
+
 class ExternalReferenceEncoder {
  public:
   ExternalReferenceEncoder();
@@ -544,6 +590,7 @@
     ASSERT(!o->IsScript());
     return o->IsString() || o->IsSharedFunctionInfo() ||
            o->IsHeapNumber() || o->IsCode() ||
+           o->IsSerializedScopeInfo() ||
            o->map() == HEAP->fixed_cow_array_map();
   }
 
diff --git a/src/small-pointer-list.h b/src/small-pointer-list.h
index 6291d9e..6c5ce89 100644
--- a/src/small-pointer-list.h
+++ b/src/small-pointer-list.h
@@ -44,6 +44,31 @@
  public:
   SmallPointerList() : data_(kEmptyTag) {}
 
+  explicit SmallPointerList(int capacity) : data_(kEmptyTag) {
+    Reserve(capacity);
+  }
+
+  void Reserve(int capacity) {
+    if (capacity < 2) return;
+    if ((data_ & kTagMask) == kListTag) {
+      if (list()->capacity() >= capacity) return;
+      int old_length = list()->length();
+      list()->AddBlock(NULL, capacity - list()->capacity());
+      list()->Rewind(old_length);
+      return;
+    }
+    PointerList* list = new PointerList(capacity);
+    if ((data_ & kTagMask) == kSingletonTag) {
+      list->Add(single_value());
+    }
+    ASSERT(IsAligned(reinterpret_cast<intptr_t>(list), kPointerAlignment));
+    data_ = reinterpret_cast<intptr_t>(list) | kListTag;
+  }
+
+  void Clear() {
+    data_ = kEmptyTag;
+  }
+
   bool is_empty() const { return length() == 0; }
 
   int length() const {
diff --git a/src/spaces-inl.h b/src/spaces-inl.h
index 0eb827d..35d7224 100644
--- a/src/spaces-inl.h
+++ b/src/spaces-inl.h
@@ -295,13 +295,13 @@
   SetPageFlag(IS_NORMAL_PAGE, !is_large_object_page);
 }
 
-bool Page::IsPageExecutable() {
-  return GetPageFlag(IS_EXECUTABLE);
+Executability Page::PageExecutability() {
+  return GetPageFlag(IS_EXECUTABLE) ? EXECUTABLE : NOT_EXECUTABLE;
 }
 
 
-void Page::SetIsPageExecutable(bool is_page_executable) {
-  SetPageFlag(IS_EXECUTABLE, is_page_executable);
+void Page::SetPageExecutability(Executability executable) {
+  SetPageFlag(IS_EXECUTABLE, executable == EXECUTABLE);
 }
 
 
@@ -435,23 +435,6 @@
 
 
 // -----------------------------------------------------------------------------
-// LargeObjectChunk
-
-Address LargeObjectChunk::GetStartAddress() {
-  // Round the chunk address up to the nearest page-aligned address
-  // and return the heap object in that page.
-  Page* page = Page::FromAddress(RoundUp(address(), Page::kPageSize));
-  return page->ObjectAreaStart();
-}
-
-
-void LargeObjectChunk::Free(Executability executable) {
-  Isolate* isolate =
-      Page::FromAddress(RoundUp(address(), Page::kPageSize))->heap_->isolate();
-  isolate->memory_allocator()->FreeRawMemory(address(), size(), executable);
-}
-
-// -----------------------------------------------------------------------------
 // NewSpace
 
 MaybeObject* NewSpace::AllocateRawInternal(int size_in_bytes,
diff --git a/src/spaces.cc b/src/spaces.cc
index 0f80496..97c6d2a 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -148,12 +148,12 @@
 // CodeRange
 
 
-CodeRange::CodeRange()
-    : code_range_(NULL),
+CodeRange::CodeRange(Isolate* isolate)
+    : isolate_(isolate),
+      code_range_(NULL),
       free_list_(0),
       allocation_list_(0),
-      current_allocation_block_index_(0),
-      isolate_(NULL) {
+      current_allocation_block_index_(0) {
 }
 
 
@@ -279,8 +279,9 @@
 const int kEstimatedNumberOfChunks = 270;
 
 
-MemoryAllocator::MemoryAllocator()
-    : capacity_(0),
+MemoryAllocator::MemoryAllocator(Isolate* isolate)
+    : isolate_(isolate),
+      capacity_(0),
       capacity_executable_(0),
       size_(0),
       size_executable_(0),
@@ -288,8 +289,7 @@
       chunks_(kEstimatedNumberOfChunks),
       free_chunk_ids_(kEstimatedNumberOfChunks),
       max_nof_chunks_(0),
-      top_(0),
-      isolate_(NULL) {
+      top_(0) {
 }
 
 
@@ -1542,6 +1542,7 @@
       CASE(UNARY_OP_IC);
       CASE(BINARY_OP_IC);
       CASE(COMPARE_IC);
+      CASE(TO_BOOLEAN_IC);
     }
   }
 
@@ -2721,12 +2722,26 @@
 
   LargeObjectChunk* chunk = reinterpret_cast<LargeObjectChunk*>(mem);
   chunk->size_ = size;
-  Page* page = Page::FromAddress(RoundUp(chunk->address(), Page::kPageSize));
-  page->heap_ = isolate->heap();
+  chunk->GetPage()->heap_ = isolate->heap();
   return chunk;
 }
 
 
+void LargeObjectChunk::Free(Executability executable) {
+  size_t guard_size = (executable == EXECUTABLE) ? Page::kPageSize : 0;
+  ObjectSpace space =
+      (executable == EXECUTABLE) ? kObjectSpaceCodeSpace : kObjectSpaceLoSpace;
+  // Do not access instance fields after FreeRawMemory!
+  Address my_address = address();
+  size_t my_size = size();
+  Isolate* isolate = GetPage()->heap_->isolate();
+  MemoryAllocator* a = isolate->memory_allocator();
+  a->FreeRawMemory(my_address - guard_size, my_size + guard_size, executable);
+  a->PerformAllocationCallback(space, kAllocationActionFree, my_size);
+  LOG(isolate, DeleteEvent("LargeObjectChunk", my_address));
+}
+
+
 int LargeObjectChunk::ChunkSizeFor(int size_in_bytes) {
   int os_alignment = static_cast<int>(OS::AllocateAlignment());
   if (os_alignment < Page::kPageSize) {
@@ -2759,25 +2774,9 @@
   while (first_chunk_ != NULL) {
     LargeObjectChunk* chunk = first_chunk_;
     first_chunk_ = first_chunk_->next();
-    LOG(heap()->isolate(), DeleteEvent("LargeObjectChunk", chunk->address()));
-    Page* page = Page::FromAddress(RoundUp(chunk->address(), Page::kPageSize));
-    Executability executable =
-        page->IsPageExecutable() ? EXECUTABLE : NOT_EXECUTABLE;
-    ObjectSpace space = kObjectSpaceLoSpace;
-    if (executable == EXECUTABLE) space = kObjectSpaceCodeSpace;
-    size_t size = chunk->size();
-    size_t guard_size = (executable == EXECUTABLE) ? Page::kPageSize : 0;
-    heap()->isolate()->memory_allocator()->FreeRawMemory(
-        chunk->address() - guard_size,
-        size + guard_size,
-        executable);
-    heap()->isolate()->memory_allocator()->PerformAllocationCallback(
-        space, kAllocationActionFree, size);
+    chunk->Free(chunk->GetPage()->PageExecutability());
   }
-
-  size_ = 0;
-  page_count_ = 0;
-  objects_size_ = 0;
+  Setup();
 }
 
 
@@ -2805,14 +2804,14 @@
   first_chunk_ = chunk;
 
   // Initialize page header.
-  Page* page = Page::FromAddress(RoundUp(chunk->address(), Page::kPageSize));
+  Page* page = chunk->GetPage();
   Address object_address = page->ObjectAreaStart();
 
   // Clear the low order bit of the second word in the page to flag it as a
   // large object page.  If the chunk_size happened to be written there, its
   // low order bit should already be clear.
   page->SetIsLargeObjectPage(true);
-  page->SetIsPageExecutable(executable);
+  page->SetPageExecutability(executable);
   page->SetRegionMarks(Page::kAllRegionsCleanMarks);
   return HeapObject::FromAddress(object_address);
 }
@@ -2943,14 +2942,8 @@
       previous = current;
       current = current->next();
     } else {
-      Page* page = Page::FromAddress(RoundUp(current->address(),
-                                     Page::kPageSize));
-      Executability executable =
-          page->IsPageExecutable() ? EXECUTABLE : NOT_EXECUTABLE;
-      Address chunk_address = current->address();
-      size_t chunk_size = current->size();
-
       // Cut the chunk out from the chunk list.
+      LargeObjectChunk* current_chunk = current;
       current = current->next();
       if (previous == NULL) {
         first_chunk_ = current;
@@ -2963,22 +2956,10 @@
           object, heap()->isolate());
       LiveObjectList::ProcessNonLive(object);
 
-      size_ -= static_cast<int>(chunk_size);
+      size_ -= static_cast<int>(current_chunk->size());
       objects_size_ -= object->Size();
       page_count_--;
-      ObjectSpace space = kObjectSpaceLoSpace;
-      size_t guard_size = 0;
-      if (executable == EXECUTABLE) {
-        space = kObjectSpaceCodeSpace;
-        guard_size = Page::kPageSize;
-      }
-      heap()->isolate()->memory_allocator()->FreeRawMemory(
-          chunk_address - guard_size,
-          chunk_size + guard_size,
-          executable);
-      heap()->isolate()->memory_allocator()->PerformAllocationCallback(
-          space, kAllocationActionFree, size_);
-      LOG(heap()->isolate(), DeleteEvent("LargeObjectChunk", chunk_address));
+      current_chunk->Free(current_chunk->GetPage()->PageExecutability());
     }
   }
 }
diff --git a/src/spaces.h b/src/spaces.h
index ac5d998..908cd30 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -200,9 +200,9 @@
 
   inline void SetIsLargeObjectPage(bool is_large_object_page);
 
-  inline bool IsPageExecutable();
+  inline Executability PageExecutability();
 
-  inline void SetIsPageExecutable(bool is_page_executable);
+  inline void SetPageExecutability(Executability executable);
 
   // Returns the offset of a given address to this page.
   INLINE(int Offset(Address a)) {
@@ -408,6 +408,9 @@
 // manages a range of virtual memory.
 class CodeRange {
  public:
+  explicit CodeRange(Isolate* isolate);
+  ~CodeRange() { TearDown(); }
+
   // Reserves a range of virtual memory, but does not commit any of it.
   // Can only be called once, at heap initialization time.
   // Returns false on failure.
@@ -417,9 +420,9 @@
   // manage it.
   void TearDown();
 
-  bool exists() { return code_range_ != NULL; }
+  bool exists() { return this != NULL && code_range_ != NULL; }
   bool contains(Address address) {
-    if (code_range_ == NULL) return false;
+    if (this == NULL || code_range_ == NULL) return false;
     Address start = static_cast<Address>(code_range_->address());
     return start <= address && address < start + code_range_->size();
   }
@@ -432,7 +435,7 @@
   void FreeRawMemory(void* buf, size_t length);
 
  private:
-  CodeRange();
+  Isolate* isolate_;
 
   // The reserved range of virtual memory that all code objects are put in.
   VirtualMemory* code_range_;
@@ -466,10 +469,6 @@
   static int CompareFreeBlockAddress(const FreeBlock* left,
                                      const FreeBlock* right);
 
-  friend class Isolate;
-
-  Isolate* isolate_;
-
   DISALLOW_COPY_AND_ASSIGN(CodeRange);
 };
 
@@ -500,6 +499,8 @@
 
 class MemoryAllocator {
  public:
+  explicit MemoryAllocator(Isolate* isolate);
+
   // Initializes its internal bookkeeping structures.
   // Max capacity of the total space and executable memory limit.
   bool Setup(intptr_t max_capacity, intptr_t capacity_executable);
@@ -657,10 +658,10 @@
 #endif
 
  private:
-  MemoryAllocator();
-
   static const int kChunkSize = kPagesPerChunk * Page::kPageSize;
 
+  Isolate* isolate_;
+
   // Maximum space size in bytes.
   intptr_t capacity_;
   // Maximum subset of capacity_ that can be executable
@@ -753,10 +754,6 @@
                            Page* prev,
                            Page** last_page_in_use);
 
-  friend class Isolate;
-
-  Isolate* isolate_;
-
   DISALLOW_COPY_AND_ASSIGN(MemoryAllocator);
 };
 
@@ -2147,7 +2144,7 @@
   static LargeObjectChunk* New(int size_in_bytes, Executability executable);
 
   // Free the memory associated with the chunk.
-  inline void Free(Executability executable);
+  void Free(Executability executable);
 
   // Interpret a raw address as a large object chunk.
   static LargeObjectChunk* FromAddress(Address address) {
@@ -2157,13 +2154,17 @@
   // Returns the address of this chunk.
   Address address() { return reinterpret_cast<Address>(this); }
 
+  Page* GetPage() {
+    return Page::FromAddress(RoundUp(address(), Page::kPageSize));
+  }
+
   // Accessors for the fields of the chunk.
   LargeObjectChunk* next() { return next_; }
   void set_next(LargeObjectChunk* chunk) { next_ = chunk; }
   size_t size() { return size_ & ~Page::kPageFlagMask; }
 
   // Compute the start address in the chunk.
-  inline Address GetStartAddress();
+  Address GetStartAddress() { return GetPage()->ObjectAreaStart(); }
 
   // Returns the object in this chunk.
   HeapObject* GetObject() { return HeapObject::FromAddress(GetStartAddress()); }
diff --git a/src/string.js b/src/string.js
index 600b131..a70eead 100644
--- a/src/string.js
+++ b/src/string.js
@@ -149,7 +149,7 @@
         position = 0;
       }
       if (position + patLength < subLength) {
-        index = position
+        index = position;
       }
     }
   }
@@ -170,7 +170,7 @@
                         ["String.prototype.localeCompare"]);
   }
   if (%_ArgumentsLength() === 0) return 0;
-  return %StringLocaleCompare(TO_STRING_INLINE(this), 
+  return %StringLocaleCompare(TO_STRING_INLINE(this),
                               TO_STRING_INLINE(other));
 }
 
@@ -251,8 +251,7 @@
 
   // Compute the string to replace with.
   if (IS_FUNCTION(replace)) {
-    var receiver =
-        %_IsNativeOrStrictMode(replace) ? void 0 : %GetGlobalReceiver();
+    var receiver = %GetDefaultReceiver(replace);
     builder.add(%_CallFunction(receiver,
                                search,
                                start,
@@ -420,8 +419,7 @@
   if (NUMBER_OF_CAPTURES(lastMatchInfo) == 2) {
     var match_start = 0;
     var override = new InternalArray(null, 0, subject);
-    var receiver =
-        %_IsNativeOrStrictMode(replace) ? void 0 : %GetGlobalReceiver();
+    var receiver = %GetDefaultReceiver(replace);
     while (i < len) {
       var elem = res[i];
       if (%_IsSmi(elem)) {
@@ -478,8 +476,7 @@
     // No captures, only the match, which is always valid.
     var s = SubString(subject, index, endOfMatch);
     // Don't call directly to avoid exposing the built-in global object.
-    var receiver =
-        %_IsNativeOrStrictMode(replace) ? void 0 : %GetGlobalReceiver();
+    var receiver = %GetDefaultReceiver(replace);
     replacement =
         %_CallFunction(receiver, s, index, subject, replace);
   } else {
diff --git a/src/stub-cache.cc b/src/stub-cache.cc
index 79cd7a0..13b0b63 100644
--- a/src/stub-cache.cc
+++ b/src/stub-cache.cc
@@ -29,6 +29,7 @@
 
 #include "api.h"
 #include "arguments.h"
+#include "ast.h"
 #include "code-stubs.h"
 #include "gdb-jit.h"
 #include "ic-inl.h"
@@ -1161,7 +1162,7 @@
 }
 
 
-void StubCache::CollectMatchingMaps(ZoneMapList* types,
+void StubCache::CollectMatchingMaps(SmallMapList* types,
                                     String* name,
                                     Code::Flags flags) {
   for (int i = 0; i < kPrimaryTableSize; i++) {
diff --git a/src/stub-cache.h b/src/stub-cache.h
index ffe4241..dd06a1c 100644
--- a/src/stub-cache.h
+++ b/src/stub-cache.h
@@ -46,8 +46,10 @@
 // invalidate the cache whenever a prototype map is changed.  The stub
 // validates the map chain as in the mono-morphic case.
 
+class SmallMapList;
 class StubCache;
 
+
 class SCTableReference {
  public:
   Address address() const { return address_; }
@@ -294,7 +296,7 @@
   void Clear();
 
   // Collect all maps that match the name and flags.
-  void CollectMatchingMaps(ZoneMapList* types,
+  void CollectMatchingMaps(SmallMapList* types,
                            String* name,
                            Code::Flags flags);
 
@@ -355,7 +357,7 @@
     // shift are equal.  Shifting down the length field to get the
     // hash code would effectively throw away two bits of the hash
     // code.
-    ASSERT(kHeapObjectTagSize == String::kHashShift);
+    STATIC_ASSERT(kHeapObjectTagSize == String::kHashShift);
     // Compute the hash of the name (use entire hash field).
     ASSERT(name->HasHashCode());
     uint32_t field = name->hash_field();
diff --git a/src/token.cc b/src/token.cc
index feca7be..7ba7ed3 100644
--- a/src/token.cc
+++ b/src/token.cc
@@ -33,21 +33,21 @@
 
 #define T(name, string, precedence) #name,
 const char* const Token::name_[NUM_TOKENS] = {
-  TOKEN_LIST(T, T, IGNORE_TOKEN)
+  TOKEN_LIST(T, T)
 };
 #undef T
 
 
 #define T(name, string, precedence) string,
 const char* const Token::string_[NUM_TOKENS] = {
-  TOKEN_LIST(T, T, IGNORE_TOKEN)
+  TOKEN_LIST(T, T)
 };
 #undef T
 
 
 #define T(name, string, precedence) precedence,
 const int8_t Token::precedence_[NUM_TOKENS] = {
-  TOKEN_LIST(T, T, IGNORE_TOKEN)
+  TOKEN_LIST(T, T)
 };
 #undef T
 
@@ -55,7 +55,7 @@
 #define KT(a, b, c) 'T',
 #define KK(a, b, c) 'K',
 const char Token::token_type[] = {
-  TOKEN_LIST(KT, KK, IGNORE_TOKEN)
+  TOKEN_LIST(KT, KK)
 };
 #undef KT
 #undef KK
diff --git a/src/token.h b/src/token.h
index 77333bc..eb825c1 100644
--- a/src/token.h
+++ b/src/token.h
@@ -41,7 +41,6 @@
 //
 //   T: Non-keyword tokens
 //   K: Keyword tokens
-//   F: Future (reserved) keyword tokens
 
 // IGNORE_TOKEN is a convenience macro that can be supplied as
 // an argument (at any position) for a TOKEN_LIST call. It does
@@ -49,7 +48,7 @@
 
 #define IGNORE_TOKEN(name, string, precedence)
 
-#define TOKEN_LIST(T, K, F)                                             \
+#define TOKEN_LIST(T, K)                                                \
   /* End of source indicator. */                                        \
   T(EOS, "EOS", 0)                                                      \
                                                                         \
@@ -72,6 +71,7 @@
   /* this block of enum values being contiguous and sorted in the */    \
   /* same order! */                                                     \
   T(INIT_VAR, "=init_var", 2)  /* AST-use only. */                      \
+  T(INIT_LET, "=init_let", 2)  /* AST-use only. */                      \
   T(INIT_CONST, "=init_const", 2)  /* AST-use only. */                  \
   T(ASSIGN, "=", 2)                                                     \
   T(ASSIGN_BIT_OR, "|=", 2)                                             \
@@ -169,6 +169,7 @@
   T(FUTURE_RESERVED_WORD, NULL, 0)                                      \
   T(FUTURE_STRICT_RESERVED_WORD, NULL, 0)                               \
   K(CONST, "const", 0)                                                  \
+  K(LET, "let", 0)                                                      \
                                                                         \
   /* Illegal token - not able to scan. */                               \
   T(ILLEGAL, "ILLEGAL", 0)                                              \
@@ -182,7 +183,7 @@
   // All token values.
 #define T(name, string, precedence) name,
   enum Value {
-    TOKEN_LIST(T, T, IGNORE_TOKEN)
+    TOKEN_LIST(T, T)
     NUM_TOKENS
   };
 #undef T
diff --git a/src/type-info.cc b/src/type-info.cc
index defb1ae..bdf7bc3 100644
--- a/src/type-info.cc
+++ b/src/type-info.cc
@@ -159,23 +159,26 @@
 }
 
 
-ZoneMapList* TypeFeedbackOracle::LoadReceiverTypes(Property* expr,
-                                                   Handle<String> name) {
+void TypeFeedbackOracle::LoadReceiverTypes(Property* expr,
+                                           Handle<String> name,
+                                           SmallMapList* types) {
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::LOAD_IC, NORMAL);
-  return CollectReceiverTypes(expr->id(), name, flags);
+  CollectReceiverTypes(expr->id(), name, flags, types);
 }
 
 
-ZoneMapList* TypeFeedbackOracle::StoreReceiverTypes(Assignment* expr,
-                                                    Handle<String> name) {
+void TypeFeedbackOracle::StoreReceiverTypes(Assignment* expr,
+                                            Handle<String> name,
+                                            SmallMapList* types) {
   Code::Flags flags = Code::ComputeMonomorphicFlags(Code::STORE_IC, NORMAL);
-  return CollectReceiverTypes(expr->id(), name, flags);
+  CollectReceiverTypes(expr->id(), name, flags, types);
 }
 
 
-ZoneMapList* TypeFeedbackOracle::CallReceiverTypes(Call* expr,
-                                                   Handle<String> name,
-                                                   CallKind call_kind) {
+void TypeFeedbackOracle::CallReceiverTypes(Call* expr,
+                                           Handle<String> name,
+                                           CallKind call_kind,
+                                           SmallMapList* types) {
   int arity = expr->arguments()->length();
 
   // Note: Currently we do not take string extra ic data into account
@@ -189,7 +192,7 @@
                                                     OWN_MAP,
                                                     NOT_IN_LOOP,
                                                     arity);
-  return CollectReceiverTypes(expr->id(), name, flags);
+  CollectReceiverTypes(expr->id(), name, flags, types);
 }
 
 
@@ -391,36 +394,30 @@
 }
 
 
-ZoneMapList* TypeFeedbackOracle::CollectReceiverTypes(unsigned ast_id,
-                                                      Handle<String> name,
-                                                      Code::Flags flags) {
+void TypeFeedbackOracle::CollectReceiverTypes(unsigned ast_id,
+                                              Handle<String> name,
+                                              Code::Flags flags,
+                                              SmallMapList* types) {
   Isolate* isolate = Isolate::Current();
   Handle<Object> object = GetInfo(ast_id);
-  if (object->IsUndefined() || object->IsSmi()) return NULL;
+  if (object->IsUndefined() || object->IsSmi()) return;
 
   if (*object == isolate->builtins()->builtin(Builtins::kStoreIC_GlobalProxy)) {
     // TODO(fschneider): We could collect the maps and signal that
     // we need a generic store (or load) here.
     ASSERT(Handle<Code>::cast(object)->ic_state() == MEGAMORPHIC);
-    return NULL;
   } else if (object->IsMap()) {
-    ZoneMapList* types = new ZoneMapList(1);
     types->Add(Handle<Map>::cast(object));
-    return types;
   } else if (Handle<Code>::cast(object)->ic_state() == MEGAMORPHIC) {
-    ZoneMapList* types = new ZoneMapList(4);
+    types->Reserve(4);
     ASSERT(object->IsCode());
     isolate->stub_cache()->CollectMatchingMaps(types, *name, flags);
-    return types->length() > 0 ? types : NULL;
-  } else {
-    return NULL;
   }
 }
 
 
-void TypeFeedbackOracle::CollectKeyedReceiverTypes(
-    unsigned ast_id,
-    ZoneMapList* types) {
+void TypeFeedbackOracle::CollectKeyedReceiverTypes(unsigned ast_id,
+                                                   SmallMapList* types) {
   Handle<Object> object = GetInfo(ast_id);
   if (!object->IsCode()) return;
   Handle<Code> code = Handle<Code>::cast(object);
@@ -439,6 +436,12 @@
 }
 
 
+byte TypeFeedbackOracle::ToBooleanTypes(unsigned ast_id) {
+  Handle<Object> object = GetInfo(ast_id);
+  return object->IsCode() ? Handle<Code>::cast(object)->to_boolean_state() : 0;
+}
+
+
 // Things are a bit tricky here: The iterator for the RelocInfos and the infos
 // themselves are not GC-safe, so we first get all infos, then we create the
 // dictionary (possibly triggering GC), and finally we relocate the collected
@@ -523,6 +526,7 @@
     case Code::UNARY_OP_IC:
     case Code::BINARY_OP_IC:
     case Code::COMPARE_IC:
+    case Code::TO_BOOLEAN_IC:
       SetInfo(ast_id, target);
       break;
 
diff --git a/src/type-info.h b/src/type-info.h
index 0a8c935..448e4c9 100644
--- a/src/type-info.h
+++ b/src/type-info.h
@@ -203,14 +203,16 @@
 
 // Forward declarations.
 class Assignment;
-class UnaryOperation;
 class BinaryOperation;
 class Call;
-class CompareOperation;
-class CountOperation;
-class CompilationInfo;
-class Property;
 class CaseClause;
+class CompareOperation;
+class CompilationInfo;
+class CountOperation;
+class Property;
+class SmallMapList;
+class UnaryOperation;
+
 
 class TypeFeedbackOracle BASE_EMBEDDED {
  public:
@@ -225,19 +227,29 @@
   Handle<Map> LoadMonomorphicReceiverType(Property* expr);
   Handle<Map> StoreMonomorphicReceiverType(Expression* expr);
 
-  ZoneMapList* LoadReceiverTypes(Property* expr, Handle<String> name);
-  ZoneMapList* StoreReceiverTypes(Assignment* expr, Handle<String> name);
-  ZoneMapList* CallReceiverTypes(Call* expr,
-                                 Handle<String> name,
-                                 CallKind call_kind);
+  void LoadReceiverTypes(Property* expr,
+                         Handle<String> name,
+                         SmallMapList* types);
+  void StoreReceiverTypes(Assignment* expr,
+                          Handle<String> name,
+                          SmallMapList* types);
+  void CallReceiverTypes(Call* expr,
+                         Handle<String> name,
+                         CallKind call_kind,
+                         SmallMapList* types);
   void CollectKeyedReceiverTypes(unsigned ast_id,
-                                 ZoneMapList* types);
+                                 SmallMapList* types);
 
   CheckType GetCallCheckType(Call* expr);
   Handle<JSObject> GetPrototypeForPrimitiveCheck(CheckType check);
 
   bool LoadIsBuiltin(Property* expr, Builtins::Name id);
 
+  // TODO(1571) We can't use ToBooleanStub::Types as the return value because
+  // of various cylces in our headers. Death to tons of implementations in
+  // headers!! :-P
+  byte ToBooleanTypes(unsigned ast_id);
+
   // Get type information for arithmetic operations and compares.
   TypeInfo UnaryType(UnaryOperation* expr);
   TypeInfo BinaryType(BinaryOperation* expr);
@@ -247,9 +259,10 @@
   TypeInfo IncrementType(CountOperation* expr);
 
  private:
-  ZoneMapList* CollectReceiverTypes(unsigned ast_id,
-                                    Handle<String> name,
-                                    Code::Flags flags);
+  void CollectReceiverTypes(unsigned ast_id,
+                            Handle<String> name,
+                            Code::Flags flags,
+                            SmallMapList* types);
 
   void SetInfo(unsigned ast_id, Object* target);
 
diff --git a/src/utils.h b/src/utils.h
index ecdf1c7..785bc43 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -30,6 +30,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <climits>
 
 #include "globals.h"
 #include "checks.h"
@@ -885,6 +886,30 @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(SimpleStringBuilder);
 };
 
+
+// A poor man's version of STL's bitset: A bit set of enums E (without explicit
+// values), fitting into an integral type T.
+template <class E, class T = int>
+class EnumSet {
+ public:
+  explicit EnumSet(T bits = 0) : bits_(bits) {}
+  bool IsEmpty() const { return bits_ == 0; }
+  bool Contains(E element) const { return (bits_ & Mask(element)) != 0; }
+  void Add(E element) { bits_ |= Mask(element); }
+  void Remove(E element) { bits_ &= ~Mask(element); }
+  T ToIntegral() const { return bits_; }
+
+ private:
+  T Mask(E element) const {
+    // The strange typing in ASSERT is necessary to avoid stupid warnings, see:
+    // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43680
+    ASSERT(element < static_cast<int>(sizeof(T) * CHAR_BIT));
+    return 1 << element;
+  }
+
+  T bits_;
+};
+
 } }  // namespace v8::internal
 
 #endif  // V8_UTILS_H_
diff --git a/src/v8.cc b/src/v8.cc
index 36f835f..1e9b5dc 100644
--- a/src/v8.cc
+++ b/src/v8.cc
@@ -28,6 +28,7 @@
 #include "v8.h"
 
 #include "isolate.h"
+#include "elements.h"
 #include "bootstrapper.h"
 #include "debug.h"
 #include "deoptimizer.h"
@@ -212,6 +213,8 @@
 
   // Peephole optimization might interfere with deoptimization.
   FLAG_peephole_optimization = !use_crankshaft_;
+
+  ElementsAccessor::InitializeOncePerProcess();
 }
 
 } }  // namespace v8::internal
diff --git a/src/v8natives.js b/src/v8natives.js
index ff87804..982e18e 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -106,13 +106,16 @@
       // Truncate number.
       return string | 0;
     }
+    string = TO_STRING_INLINE(string);
     radix = radix | 0;
   } else {
+    // The spec says ToString should be evaluated before ToInt32.
+    string = TO_STRING_INLINE(string);
     radix = TO_INT32(radix);
     if (!(radix == 0 || (2 <= radix && radix <= 36)))
       return $NaN;
   }
-  string = TO_STRING_INLINE(string);
+
   if (%_HasCachedArrayIndex(string) &&
       (radix == 0 || radix == 10)) {
     return %_GetCachedArrayIndex(string);
@@ -209,7 +212,7 @@
   if (IS_UNDEFINED(this) && !IS_UNDETECTABLE(this)) {
     return '[object Undefined]';
   }
-  if (IS_NULL(this)) return  '[object Null]';
+  if (IS_NULL(this)) return '[object Null]';
   return "[object " + %_ClassOf(ToObject(this)) + "]";
 }
 
@@ -232,6 +235,10 @@
 
 // ECMA-262 - 15.2.4.5
 function ObjectHasOwnProperty(V) {
+  if (%IsJSProxy(this)) {
+    var handler = %GetHandler(this);
+    return CallTrap1(handler, "hasOwn", DerivedHasOwnTrap, TO_STRING_INLINE(V));
+  }
   return %HasLocalProperty(TO_OBJECT_INLINE(this), TO_STRING_INLINE(V));
 }
 
@@ -249,7 +256,12 @@
 
 // ECMA-262 - 15.2.4.6
 function ObjectPropertyIsEnumerable(V) {
-  return %IsPropertyEnumerable(ToObject(this), ToString(V));
+  var P = ToString(V);
+  if (%IsJSProxy(this)) {
+    var desc = GetOwnProperty(this, P);
+    return IS_UNDEFINED(desc) ? false : desc.isEnumerable();
+  }
+  return %IsPropertyEnumerable(ToObject(this), P);
 }
 
 
@@ -310,9 +322,7 @@
     throw MakeTypeError("obj_ctor_property_non_object", ["keys"]);
   if (%IsJSProxy(obj)) {
     var handler = %GetHandler(obj);
-    var keys = handler.keys;
-    if (IS_UNDEFINED(keys)) keys = DerivedKeysTrap;
-    var names = %_CallFunction(handler, keys);
+    var names = CallTrap0(handler, "keys", DerivedKeysTrap);
     return ToStringArray(names);
   }
   return %LocalKeys(obj);
@@ -601,16 +611,42 @@
 }
 
 
+// For Harmony proxies.
+function GetTrap(handler, name, defaultTrap) {
+  var trap = handler[name];
+  if (IS_UNDEFINED(trap)) {
+    if (IS_UNDEFINED(defaultTrap)) {
+      throw MakeTypeError("handler_trap_missing", [handler, name]);
+    }
+    trap = defaultTrap;
+  } else if (!IS_FUNCTION(trap)) {
+    throw MakeTypeError("handler_trap_must_be_callable", [handler, name]);
+  }
+  return trap;
+}
+
+
+function CallTrap0(handler, name, defaultTrap) {
+  return %_CallFunction(handler, GetTrap(handler, name, defaultTrap));
+}
+
+
+function CallTrap1(handler, name, defaultTrap, x) {
+  return %_CallFunction(handler, x, GetTrap(handler, name, defaultTrap));
+}
+
+
+function CallTrap2(handler, name, defaultTrap, x, y) {
+  return %_CallFunction(handler, x, y, GetTrap(handler, name, defaultTrap));
+}
+
+
 // ES5 section 8.12.1.
-function GetOwnProperty(obj, p) {
+function GetOwnProperty(obj, v) {
+  var p = ToString(v);
   if (%IsJSProxy(obj)) {
     var handler = %GetHandler(obj);
-    var getOwnProperty = handler.getOwnPropertyDescriptor;
-    if (IS_UNDEFINED(getOwnProperty)) {
-      throw MakeTypeError("handler_trap_missing",
-                          [handler, "getOwnPropertyDescriptor"]);
-    }
-    var descriptor = %_CallFunction(handler, p, getOwnProperty);
+    var descriptor = CallTrap1(handler, "getOwnPropertyDescriptor", void 0, p);
     if (IS_UNDEFINED(descriptor)) return descriptor;
     var desc = ToCompletePropertyDescriptor(descriptor);
     if (!desc.isConfigurable()) {
@@ -623,7 +659,7 @@
   // GetOwnProperty returns an array indexed by the constants
   // defined in macros.py.
   // If p is not a property on obj undefined is returned.
-  var props = %GetOwnProperty(ToObject(obj), ToString(p));
+  var props = %GetOwnProperty(ToObject(obj), ToString(v));
 
   // A false value here means that access checks failed.
   if (props === false) return void 0;
@@ -635,11 +671,7 @@
 // Harmony proxies.
 function DefineProxyProperty(obj, p, attributes, should_throw) {
   var handler = %GetHandler(obj);
-  var defineProperty = handler.defineProperty;
-  if (IS_UNDEFINED(defineProperty)) {
-    throw MakeTypeError("handler_trap_missing", [handler, "defineProperty"]);
-  }
-  var result = %_CallFunction(handler, p, attributes, defineProperty);
+  var result = CallTrap2(handler, "defineProperty", void 0, p, attributes);
   if (!ToBoolean(result)) {
     if (should_throw) {
       throw MakeTypeError("handler_returned_false",
@@ -868,12 +900,7 @@
   // Special handling for proxies.
   if (%IsJSProxy(obj)) {
     var handler = %GetHandler(obj);
-    var getOwnPropertyNames = handler.getOwnPropertyNames;
-    if (IS_UNDEFINED(getOwnPropertyNames)) {
-      throw MakeTypeError("handler_trap_missing",
-                          [handler, "getOwnPropertyNames"]);
-    }
-    var names = %_CallFunction(handler, getOwnPropertyNames);
+    var names = CallTrap0(handler, "getOwnPropertyNames", void 0);
     return ToStringArray(names, "getOwnPropertyNames");
   }
 
@@ -977,24 +1004,27 @@
 }
 
 
+function GetOwnEnumerablePropertyNames(properties) {
+  var names = new InternalArray();
+  for (var key in properties) {
+    if (%HasLocalProperty(properties, key)) {
+      names.push(key);
+    }
+  }
+  return names;
+}
+
+
 // ES5 section 15.2.3.7.
 function ObjectDefineProperties(obj, properties) {
   if (!IS_SPEC_OBJECT(obj))
     throw MakeTypeError("obj_ctor_property_non_object", ["defineProperties"]);
   var props = ToObject(properties);
-  var key_values = [];
-  for (var key in props) {
-    if (%HasLocalProperty(props, key)) {
-      key_values.push(key);
-      var value = props[key];
-      var desc = ToPropertyDescriptor(value);
-      key_values.push(desc);
-    }
-  }
-  for (var i = 0; i < key_values.length; i += 2) {
-    var key = key_values[i];
-    var desc = key_values[i + 1];
-    DefineOwnProperty(obj, key, desc, true);
+  var names = GetOwnEnumerablePropertyNames(props);
+  for (var i = 0; i < names.length; i++) {
+    var name = names[i];
+    var desc = ToPropertyDescriptor(props[name]);
+    DefineOwnProperty(obj, name, desc, true);
   }
   return obj;
 }
@@ -1003,11 +1033,7 @@
 // Harmony proxies.
 function ProxyFix(obj) {
   var handler = %GetHandler(obj);
-  var fix = handler.fix;
-  if (IS_UNDEFINED(fix)) {
-    throw MakeTypeError("handler_trap_missing", [handler, "fix"]);
-  }
-  var props = %_CallFunction(handler, fix);
+  var props = CallTrap0(handler, "fix", void 0);
   if (IS_UNDEFINED(props)) {
     throw MakeTypeError("handler_returned_undefined", [handler, "fix"]);
   }
@@ -1466,9 +1492,9 @@
 
   // Set the correct length.
   var length = (this.length - argc_bound) > 0 ? this.length - argc_bound : 0;
-  %FunctionSetLength(result, length);
   %FunctionRemovePrototype(result);
   %FunctionSetBound(result);
+  %BoundFunctionSetLength(result, length);
   return result;
 }
 
diff --git a/src/v8threads.cc b/src/v8threads.cc
index c9a8bb6..3881d66 100644
--- a/src/v8threads.cc
+++ b/src/v8threads.cc
@@ -94,6 +94,11 @@
 }
 
 
+bool Locker::IsActive() {
+  return active_;
+}
+
+
 Locker::~Locker() {
   ASSERT(isolate_->thread_manager()->IsLockedByCurrentThread());
   if (has_lock_) {
@@ -300,7 +305,9 @@
 
 
 ThreadManager::~ThreadManager() {
-  // TODO(isolates): Destroy mutexes.
+  delete mutex_;
+  delete free_anchor_;
+  delete in_use_anchor_;
 }
 
 
diff --git a/src/variables.cc b/src/variables.cc
index 67150ea..e82e674 100644
--- a/src/variables.cc
+++ b/src/variables.cc
@@ -41,6 +41,7 @@
   switch (mode) {
     case VAR: return "VAR";
     case CONST: return "CONST";
+    case LET: return "LET";
     case DYNAMIC: return "DYNAMIC";
     case DYNAMIC_GLOBAL: return "DYNAMIC_GLOBAL";
     case DYNAMIC_LOCAL: return "DYNAMIC_LOCAL";
diff --git a/src/variables.h b/src/variables.h
index a9c06d1..2095555 100644
--- a/src/variables.h
+++ b/src/variables.h
@@ -46,6 +46,8 @@
 
     CONST,     // declared via 'const' declarations
 
+    LET,       // declared via 'let' declarations
+
     // Variables introduced by the compiler:
     DYNAMIC,         // always require dynamic lookup (we don't know
                      // the declaration)
@@ -99,6 +101,7 @@
     return is_accessed_from_inner_scope_;
   }
   void MarkAsAccessedFromInnerScope() {
+    ASSERT(mode_ != TEMPORARY);
     is_accessed_from_inner_scope_ = true;
   }
   bool is_used() { return is_used_; }
diff --git a/src/version.cc b/src/version.cc
index fcf6f88..1a7c751 100644
--- a/src/version.cc
+++ b/src/version.cc
@@ -33,9 +33,9 @@
 // NOTE these macros are used by the SCons build script so their names
 // cannot be changed without changing the SCons build script.
 #define MAJOR_VERSION     3
-#define MINOR_VERSION     4
-#define BUILD_NUMBER      14
-#define PATCH_LEVEL       35
+#define MINOR_VERSION     5
+#define BUILD_NUMBER      10
+#define PATCH_LEVEL       24
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
 #define IS_CANDIDATE_VERSION 0
diff --git a/src/weakmap.js b/src/weakmap.js
new file mode 100644
index 0000000..3d261e5
--- /dev/null
+++ b/src/weakmap.js
@@ -0,0 +1,103 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This file relies on the fact that the following declaration has been made
+// in runtime.js:
+// const $Object = global.Object;
+const $WeakMap = global.WeakMap;
+
+// -------------------------------------------------------------------
+
+function WeakMapConstructor() {
+  if (%_IsConstructCall()) {
+    %WeakMapInitialize(this);
+  } else {
+    return new $WeakMap();
+  }
+}
+
+
+function WeakMapGet(key) {
+  if (!IS_SPEC_OBJECT(key)) {
+    throw %MakeTypeError('invalid_weakmap_key', [this, key]);
+  }
+  return %WeakMapGet(this, key);
+}
+
+
+function WeakMapSet(key, value) {
+  if (!IS_SPEC_OBJECT(key)) {
+    throw %MakeTypeError('invalid_weakmap_key', [this, key]);
+  }
+  return %WeakMapSet(this, key, value);
+}
+
+
+function WeakMapHas(key) {
+  if (!IS_SPEC_OBJECT(key)) {
+    throw %MakeTypeError('invalid_weakmap_key', [this, key]);
+  }
+  return !IS_UNDEFINED(%WeakMapGet(this, key));
+}
+
+
+function WeakMapDelete(key) {
+  if (!IS_SPEC_OBJECT(key)) {
+    throw %MakeTypeError('invalid_weakmap_key', [this, key]);
+  }
+  if (!IS_UNDEFINED(%WeakMapGet(this, key))) {
+    %WeakMapSet(this, key, void 0);
+    return true;
+  } else {
+    return false;
+  }
+}
+
+// -------------------------------------------------------------------
+
+function SetupWeakMap() {
+  // Set up the WeakMap constructor function.
+  %SetCode($WeakMap, WeakMapConstructor);
+
+  // Set up the WeakMap prototype object.
+  %FunctionSetPrototype($WeakMap, new $WeakMap());
+
+  // Set up the constructor property on the WeakMap prototype object.
+  %SetProperty($WeakMap.prototype, "constructor", $WeakMap, DONT_ENUM);
+
+  // Set up the non-enumerable functions on the WeakMap prototype object.
+  InstallFunctionsOnHiddenPrototype($WeakMap.prototype, DONT_ENUM, $Array(
+    "get", WeakMapGet,
+    "set", WeakMapSet,
+    "has", WeakMapHas,
+    "delete", WeakMapDelete
+  ));
+}
+
+
+SetupWeakMap();
diff --git a/src/x64/builtins-x64.cc b/src/x64/builtins-x64.cc
index 0763989..7c6f7e3 100644
--- a/src/x64/builtins-x64.cc
+++ b/src/x64/builtins-x64.cc
@@ -139,7 +139,7 @@
     // rdi: constructor
     __ movq(rax, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
     // Will both indicate a NULL and a Smi
-    ASSERT(kSmiTag == 0);
+    STATIC_ASSERT(kSmiTag == 0);
     __ JumpIfSmi(rax, &rt_call);
     // rdi: constructor
     // rax: initial map (if proven valid below)
@@ -1283,7 +1283,7 @@
     // Initial map for the builtin Array functions should be maps.
     __ movq(rbx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
     // Will both indicate a NULL and a Smi.
-    ASSERT(kSmiTag == 0);
+    STATIC_ASSERT(kSmiTag == 0);
     Condition not_smi = NegateCondition(masm->CheckSmi(rbx));
     __ Check(not_smi, "Unexpected initial map for Array function");
     __ CmpObjectType(rbx, MAP_TYPE, rcx);
@@ -1317,7 +1317,7 @@
     // Initial map for the builtin Array function should be a map.
     __ movq(rbx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
     // Will both indicate a NULL and a Smi.
-    ASSERT(kSmiTag == 0);
+    STATIC_ASSERT(kSmiTag == 0);
     Condition not_smi = NegateCondition(masm->CheckSmi(rbx));
     __ Check(not_smi, "Unexpected initial map for Array function");
     __ CmpObjectType(rbx, MAP_TYPE, rcx);
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 1a6efcb..9237a0a 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -230,68 +230,139 @@
 }
 
 
-// The stub returns zero for false, and a non-zero value for true.
+// The stub expects its argument on the stack and returns its result in tos_:
+// zero for false, and a non-zero value for true.
 void ToBooleanStub::Generate(MacroAssembler* masm) {
-  Label false_result, true_result, not_string;
+  Label patch;
+  const Register argument = rax;
   const Register map = rdx;
 
-  __ movq(rax, Operand(rsp, 1 * kPointerSize));
+  if (!types_.IsEmpty()) {
+    __ movq(argument, Operand(rsp, 1 * kPointerSize));
+  }
 
   // undefined -> false
-  __ CompareRoot(rax, Heap::kUndefinedValueRootIndex);
-  __ j(equal, &false_result);
+  CheckOddball(masm, UNDEFINED, Heap::kUndefinedValueRootIndex, false);
 
   // Boolean -> its value
-  __ CompareRoot(rax, Heap::kFalseValueRootIndex);
-  __ j(equal, &false_result);
-  __ CompareRoot(rax, Heap::kTrueValueRootIndex);
-  __ j(equal, &true_result);
-
-  // Smis: 0 -> false, all other -> true
-  __ Cmp(rax, Smi::FromInt(0));
-  __ j(equal, &false_result);
-  __ JumpIfSmi(rax, &true_result);
+  CheckOddball(masm, BOOLEAN, Heap::kFalseValueRootIndex, false);
+  CheckOddball(masm, BOOLEAN, Heap::kTrueValueRootIndex, true);
 
   // 'null' -> false.
-  __ CompareRoot(rax, Heap::kNullValueRootIndex);
-  __ j(equal, &false_result, Label::kNear);
+  CheckOddball(masm, NULL_TYPE, Heap::kNullValueRootIndex, false);
 
-  // Get the map of the heap object.
-  __ movq(map, FieldOperand(rax, HeapObject::kMapOffset));
+  if (types_.Contains(SMI)) {
+    // Smis: 0 -> false, all other -> true
+    Label not_smi;
+    __ JumpIfNotSmi(argument, &not_smi, Label::kNear);
+    // argument contains the correct return value already
+    if (!tos_.is(argument)) {
+      __ movq(tos_, argument);
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&not_smi);
+  } else if (types_.NeedsMap()) {
+    // If we need a map later and have a Smi -> patch.
+    __ JumpIfSmi(argument, &patch, Label::kNear);
+  }
 
-  // Undetectable -> false.
-  __ testb(FieldOperand(map, Map::kBitFieldOffset),
-           Immediate(1 << Map::kIsUndetectable));
-  __ j(not_zero, &false_result, Label::kNear);
+  if (types_.NeedsMap()) {
+    __ movq(map, FieldOperand(argument, HeapObject::kMapOffset));
 
-  // JavaScript object -> true.
-  __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
-  __ j(above_equal, &true_result, Label::kNear);
+    if (types_.CanBeUndetectable()) {
+      __ testb(FieldOperand(map, Map::kBitFieldOffset),
+               Immediate(1 << Map::kIsUndetectable));
+      // Undetectable -> false.
+      Label not_undetectable;
+      __ j(zero, &not_undetectable, Label::kNear);
+      __ Set(tos_, 0);
+      __ ret(1 * kPointerSize);
+      __ bind(&not_undetectable);
+    }
+  }
 
-  // String value -> false iff empty.
-  __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
-  __ j(above_equal, &not_string, Label::kNear);
-  __ cmpq(FieldOperand(rax, String::kLengthOffset), Immediate(0));
-  __ j(zero, &false_result, Label::kNear);
-  __ jmp(&true_result, Label::kNear);
+  if (types_.Contains(SPEC_OBJECT)) {
+    // spec object -> true.
+    Label not_js_object;
+    __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
+    __ j(below, &not_js_object, Label::kNear);
+    // argument contains the correct return value already.
+    if (!tos_.is(argument)) {
+      __ Set(tos_, 1);
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&not_js_object);
+  }
 
-  __ bind(&not_string);
-  // HeapNumber -> false iff +0, -0, or NaN.
-  // These three cases set the zero flag when compared to zero using ucomisd.
-  __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
-  __ j(not_equal, &true_result, Label::kNear);
-  __ xorps(xmm0, xmm0);
-  __ ucomisd(xmm0, FieldOperand(rax, HeapNumber::kValueOffset));
-  __ j(zero, &false_result, Label::kNear);
-  // Fall through to |true_result|.
+  if (types_.Contains(STRING)) {
+    // String value -> false iff empty.
+    Label not_string;
+    __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
+    __ j(above_equal, &not_string, Label::kNear);
+    __ movq(tos_, FieldOperand(argument, String::kLengthOffset));
+    __ ret(1 * kPointerSize);  // the string length is OK as the return value
+    __ bind(&not_string);
+  }
 
-  // Return 1/0 for true/false in tos_.
-  __ bind(&true_result);
-  __ Set(tos_, 1);
-  __ ret(1 * kPointerSize);
-  __ bind(&false_result);
-  __ Set(tos_, 0);
-  __ ret(1 * kPointerSize);
+  if (types_.Contains(HEAP_NUMBER)) {
+    // heap number -> false iff +0, -0, or NaN.
+    Label not_heap_number, false_result;
+    __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
+    __ j(not_equal, &not_heap_number, Label::kNear);
+    __ xorps(xmm0, xmm0);
+    __ ucomisd(xmm0, FieldOperand(argument, HeapNumber::kValueOffset));
+    __ j(zero, &false_result, Label::kNear);
+    // argument contains the correct return value already.
+    if (!tos_.is(argument)) {
+      __ Set(tos_, 1);
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&false_result);
+    __ Set(tos_, 0);
+    __ ret(1 * kPointerSize);
+    __ bind(&not_heap_number);
+  }
+
+  __ bind(&patch);
+  GenerateTypeTransition(masm);
+}
+
+
+void ToBooleanStub::CheckOddball(MacroAssembler* masm,
+                                 Type type,
+                                 Heap::RootListIndex value,
+                                 bool result) {
+  const Register argument = rax;
+  if (types_.Contains(type)) {
+    // If we see an expected oddball, return its ToBoolean value tos_.
+    Label different_value;
+    __ CompareRoot(argument, value);
+    __ j(not_equal, &different_value, Label::kNear);
+    if (!result) {
+      // If we have to return zero, there is no way around clearing tos_.
+      __ Set(tos_, 0);
+    } else if (!tos_.is(argument)) {
+      // If we have to return non-zero, we can re-use the argument if it is the
+      // same register as the result, because we never see Smi-zero here.
+      __ Set(tos_, 1);
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&different_value);
+  }
+}
+
+
+void ToBooleanStub::GenerateTypeTransition(MacroAssembler* masm) {
+  __ pop(rcx);  // Get return address, operand is now on top of stack.
+  __ Push(Smi::FromInt(tos_.code()));
+  __ Push(Smi::FromInt(types_.ToByte()));
+  __ push(rcx);  // Push return address.
+  // Patch the caller to an appropriate specialized stub and return the
+  // operation result to the caller of the stub.
+  __ TailCallExternalReference(
+      ExternalReference(IC_Utility(IC::kToBoolean_Patch), masm->isolate()),
+      3,
+      1);
 }
 
 
@@ -2303,7 +2374,6 @@
   __ testq(kScratchRegister, kScratchRegister);
   __ j(zero, &runtime);
 
-
   // Check that the first argument is a JSRegExp object.
   __ movq(rax, Operand(rsp, kJSRegExpOffset));
   __ JumpIfSmi(rax, &runtime);
@@ -2374,10 +2444,14 @@
   __ cmpl(rdx, rdi);
   __ j(greater, &runtime);
 
+  // Reset offset for possibly sliced string.
+  __ Set(r14, 0);
   // rax: RegExp data (FixedArray)
   // Check the representation and encoding of the subject string.
   Label seq_ascii_string, seq_two_byte_string, check_code;
   __ movq(rdi, Operand(rsp, kSubjectOffset));
+  // Make a copy of the original subject string.
+  __ movq(r15, rdi);
   __ movq(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
   __ movzxbl(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
   // First check for flat two byte string.
@@ -2386,28 +2460,40 @@
   STATIC_ASSERT((kStringTag | kSeqStringTag | kTwoByteStringTag) == 0);
   __ j(zero, &seq_two_byte_string, Label::kNear);
   // Any other flat string must be a flat ascii string.
-  __ testb(rbx, Immediate(kIsNotStringMask | kStringRepresentationMask));
+  __ andb(rbx, Immediate(kIsNotStringMask | kStringRepresentationMask));
   __ j(zero, &seq_ascii_string, Label::kNear);
 
-  // Check for flat cons string.
+  // Check for flat cons string or sliced string.
   // A flat cons string is a cons string where the second part is the empty
   // string. In that case the subject string is just the first part of the cons
   // string. Also in this case the first part of the cons string is known to be
   // a sequential string or an external string.
-  STATIC_ASSERT(kExternalStringTag !=0);
-  STATIC_ASSERT((kConsStringTag & kExternalStringTag) == 0);
-  __ testb(rbx, Immediate(kIsNotStringMask | kExternalStringTag));
-  __ j(not_zero, &runtime);
-  // String is a cons string.
+  // In the case of a sliced string its offset has to be taken into account.
+  Label cons_string, check_encoding;
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ cmpq(rbx, Immediate(kExternalStringTag));
+  __ j(less, &cons_string, Label::kNear);
+  __ j(equal, &runtime);
+
+  // String is sliced.
+  __ SmiToInteger32(r14, FieldOperand(rdi, SlicedString::kOffsetOffset));
+  __ movq(rdi, FieldOperand(rdi, SlicedString::kParentOffset));
+  // r14: slice offset
+  // r15: original subject string
+  // rdi: parent string
+  __ jmp(&check_encoding, Label::kNear);
+  // String is a cons string, check whether it is flat.
+  __ bind(&cons_string);
   __ CompareRoot(FieldOperand(rdi, ConsString::kSecondOffset),
                  Heap::kEmptyStringRootIndex);
   __ j(not_equal, &runtime);
   __ movq(rdi, FieldOperand(rdi, ConsString::kFirstOffset));
+  // rdi: first part of cons string or parent of sliced string.
+  // rbx: map of first part of cons string or map of parent of sliced string.
+  // Is first part of cons or parent of slice a flat two byte string?
+  __ bind(&check_encoding);
   __ movq(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
-  // String is a cons string with empty second part.
-  // rdi: first part of cons string.
-  // rbx: map of first part of cons string.
-  // Is first part a flat two byte string?
   __ testb(FieldOperand(rbx, Map::kInstanceTypeOffset),
            Immediate(kStringRepresentationMask | kStringEncodingMask));
   STATIC_ASSERT((kSeqStringTag | kTwoByteStringTag) == 0);
@@ -2504,33 +2590,40 @@
   // rbx: previous index
   // rcx: encoding of subject string (1 if ascii 0 if two_byte);
   // r11: code
+  // r14: slice offset
+  // r15: original subject string
 
-  // Argument 4: End of string data
-  // Argument 3: Start of string data
-  Label setup_two_byte, setup_rest;
-  __ testb(rcx, rcx);  // Last use of rcx as encoding of subject string.
-  __ j(zero, &setup_two_byte, Label::kNear);
-  __ SmiToInteger32(rcx, FieldOperand(rdi, String::kLengthOffset));
-  __ lea(arg4, FieldOperand(rdi, rcx, times_1, SeqAsciiString::kHeaderSize));
-  __ lea(arg3, FieldOperand(rdi, rbx, times_1, SeqAsciiString::kHeaderSize));
-  __ jmp(&setup_rest, Label::kNear);
-  __ bind(&setup_two_byte);
-  __ SmiToInteger32(rcx, FieldOperand(rdi, String::kLengthOffset));
-  __ lea(arg4, FieldOperand(rdi, rcx, times_2, SeqTwoByteString::kHeaderSize));
-  __ lea(arg3, FieldOperand(rdi, rbx, times_2, SeqTwoByteString::kHeaderSize));
-
-  __ bind(&setup_rest);
   // Argument 2: Previous index.
   __ movq(arg2, rbx);
 
-  // Argument 1: Subject string.
-#ifdef _WIN64
-  __ movq(arg1, rdi);
-#else
-  // Already there in AMD64 calling convention.
-  ASSERT(arg1.is(rdi));
-  USE(arg1);
-#endif
+  // Argument 4: End of string data
+  // Argument 3: Start of string data
+  Label setup_two_byte, setup_rest, got_length, length_not_from_slice;
+  // Prepare start and end index of the input.
+  // Load the length from the original sliced string if that is the case.
+  __ addq(rbx, r14);
+  __ SmiToInteger32(arg3, FieldOperand(r15, String::kLengthOffset));
+  __ addq(r14, arg3);  // Using arg3 as scratch.
+
+  // rbx: start index of the input
+  // r14: end index of the input
+  // r15: original subject string
+  __ testb(rcx, rcx);  // Last use of rcx as encoding of subject string.
+  __ j(zero, &setup_two_byte, Label::kNear);
+  __ lea(arg4, FieldOperand(rdi, r14, times_1, SeqAsciiString::kHeaderSize));
+  __ lea(arg3, FieldOperand(rdi, rbx, times_1, SeqAsciiString::kHeaderSize));
+  __ jmp(&setup_rest, Label::kNear);
+  __ bind(&setup_two_byte);
+  __ lea(arg4, FieldOperand(rdi, r14, times_2, SeqTwoByteString::kHeaderSize));
+  __ lea(arg3, FieldOperand(rdi, rbx, times_2, SeqTwoByteString::kHeaderSize));
+  __ bind(&setup_rest);
+
+  // Argument 1: Original subject string.
+  // The original subject is in the previous stack frame. Therefore we have to
+  // use rbp, which points exactly to one pointer size below the previous rsp.
+  // (Because creating a new stack frame pushes the previous rbp onto the stack
+  // and thereby moves up rsp by one kPointerSize.)
+  __ movq(arg1, r15);
 
   // Locate the code entry and call it.
   __ addq(r11, Immediate(Code::kHeaderSize - kHeapObjectTag));
@@ -3780,6 +3873,7 @@
   Label flat_string;
   Label ascii_string;
   Label got_char_code;
+  Label sliced_string;
 
   // If the receiver is a smi trigger the non-string case.
   __ JumpIfSmi(object_, receiver_not_string_);
@@ -3808,25 +3902,39 @@
   __ j(zero, &flat_string);
 
   // Handle non-flat strings.
-  __ testb(result_, Immediate(kIsConsStringMask));
-  __ j(zero, &call_runtime_);
+  __ and_(result_, Immediate(kStringRepresentationMask));
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  __ cmpb(result_, Immediate(kExternalStringTag));
+  __ j(greater, &sliced_string);
+  __ j(equal, &call_runtime_);
 
   // ConsString.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
+  Label assure_seq_string;
   __ CompareRoot(FieldOperand(object_, ConsString::kSecondOffset),
                  Heap::kEmptyStringRootIndex);
   __ j(not_equal, &call_runtime_);
   // Get the first of the two strings and load its instance type.
   __ movq(object_, FieldOperand(object_, ConsString::kFirstOffset));
+  __ jmp(&assure_seq_string, Label::kNear);
+
+  // SlicedString, unpack and add offset.
+  __ bind(&sliced_string);
+  __ addq(scratch_, FieldOperand(object_, SlicedString::kOffsetOffset));
+  __ movq(object_, FieldOperand(object_, SlicedString::kParentOffset));
+
+  __ bind(&assure_seq_string);
   __ movq(result_, FieldOperand(object_, HeapObject::kMapOffset));
   __ movzxbl(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
   // If the first cons component is also non-flat, then go to runtime.
   STATIC_ASSERT(kSeqStringTag == 0);
   __ testb(result_, Immediate(kStringRepresentationMask));
   __ j(not_zero, &call_runtime_);
+  __ jmp(&flat_string);
 
   // Check for 1-byte or 2-byte string.
   __ bind(&flat_string);
@@ -4137,6 +4245,8 @@
   __ and_(rcx, Immediate(kStringRepresentationMask));
   __ cmpl(rcx, Immediate(kExternalStringTag));
   __ j(equal, &string_add_runtime);
+  // We cannot encounter sliced strings here since:
+  STATIC_ASSERT(SlicedString::kMinLength >= String::kMinNonFlatLength);
   // Now check if both strings are ascii strings.
   // rax: first string
   // rbx: length of resulting flat string
@@ -4529,6 +4639,9 @@
 void SubStringStub::Generate(MacroAssembler* masm) {
   Label runtime;
 
+  if (FLAG_string_slices) {
+    __ jmp(&runtime);
+  }
   // Stack frame on entry.
   //  rsp[0]: return address
   //  rsp[8]: to
diff --git a/src/x64/deoptimizer-x64.cc b/src/x64/deoptimizer-x64.cc
index 2a31f28..b52e659 100644
--- a/src/x64/deoptimizer-x64.cc
+++ b/src/x64/deoptimizer-x64.cc
@@ -38,7 +38,7 @@
 namespace internal {
 
 
-int Deoptimizer::table_entry_size_ = 10;
+const int Deoptimizer::table_entry_size_ = 10;
 
 
 int Deoptimizer::patch_size() {
@@ -605,8 +605,6 @@
     output_frame->SetContinuation(
         reinterpret_cast<intptr_t>(continuation->entry()));
   }
-
-  if (output_count_ - 1 == frame_index) iterator->Done();
 }
 
 
diff --git a/src/x64/disasm-x64.cc b/src/x64/disasm-x64.cc
index 14c95bc..1b8871f 100644
--- a/src/x64/disasm-x64.cc
+++ b/src/x64/disasm-x64.cc
@@ -58,7 +58,7 @@
 };
 
 
-static ByteMnemonic two_operands_instr[] = {
+static const ByteMnemonic two_operands_instr[] = {
   { 0x00, BYTE_OPER_REG_OP_ORDER, "add" },
   { 0x01, OPER_REG_OP_ORDER,      "add" },
   { 0x02, BYTE_REG_OPER_OP_ORDER, "add" },
@@ -105,7 +105,7 @@
 };
 
 
-static ByteMnemonic zero_operands_instr[] = {
+static const ByteMnemonic zero_operands_instr[] = {
   { 0xC3, UNSET_OP_ORDER, "ret" },
   { 0xC9, UNSET_OP_ORDER, "leave" },
   { 0xF4, UNSET_OP_ORDER, "hlt" },
@@ -125,14 +125,14 @@
 };
 
 
-static ByteMnemonic call_jump_instr[] = {
+static const ByteMnemonic call_jump_instr[] = {
   { 0xE8, UNSET_OP_ORDER, "call" },
   { 0xE9, UNSET_OP_ORDER, "jmp" },
   { -1, UNSET_OP_ORDER, "" }
 };
 
 
-static ByteMnemonic short_immediate_instr[] = {
+static const ByteMnemonic short_immediate_instr[] = {
   { 0x05, UNSET_OP_ORDER, "add" },
   { 0x0D, UNSET_OP_ORDER, "or" },
   { 0x15, UNSET_OP_ORDER, "adc" },
@@ -145,7 +145,7 @@
 };
 
 
-static const char* conditional_code_suffix[] = {
+static const char* const conditional_code_suffix[] = {
   "o", "no", "c", "nc", "z", "nz", "na", "a",
   "s", "ns", "pe", "po", "l", "ge", "le", "g"
 };
@@ -193,7 +193,7 @@
   InstructionDesc instructions_[256];
   void Clear();
   void Init();
-  void CopyTable(ByteMnemonic bm[], InstructionType type);
+  void CopyTable(const ByteMnemonic bm[], InstructionType type);
   void SetTableRange(InstructionType type, byte start, byte end, bool byte_size,
                      const char* mnem);
   void AddJumpConditionalShort();
@@ -228,7 +228,8 @@
 }
 
 
-void InstructionTable::CopyTable(ByteMnemonic bm[], InstructionType type) {
+void InstructionTable::CopyTable(const ByteMnemonic bm[],
+                                 InstructionType type) {
   for (int i = 0; bm[i].b >= 0; i++) {
     InstructionDesc* id = &instructions_[bm[i].b];
     id->mnem = bm[i].mnem;
diff --git a/src/x64/frames-x64.h b/src/x64/frames-x64.h
index b14267c..7012c76 100644
--- a/src/x64/frames-x64.h
+++ b/src/x64/frames-x64.h
@@ -1,4 +1,4 @@
-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -50,12 +50,13 @@
 
 class StackHandlerConstants : public AllStatic {
  public:
-  static const int kNextOffset  = 0 * kPointerSize;
-  static const int kFPOffset    = 1 * kPointerSize;
-  static const int kStateOffset = 2 * kPointerSize;
-  static const int kPCOffset    = 3 * kPointerSize;
+  static const int kNextOffset    = 0 * kPointerSize;
+  static const int kContextOffset = 1 * kPointerSize;
+  static const int kFPOffset      = 2 * kPointerSize;
+  static const int kStateOffset   = 3 * kPointerSize;
+  static const int kPCOffset      = 4 * kPointerSize;
 
-  static const int kSize = 4 * kPointerSize;
+  static const int kSize = kPCOffset + kPointerSize;
 };
 
 
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 23c2bf8..eca349e 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -45,7 +45,6 @@
 
 
 static unsigned GetPropertyId(Property* property) {
-  if (property->is_synthetic()) return AstNode::kNoNumber;
   return property->id();
 }
 
@@ -665,95 +664,69 @@
   Comment cmnt(masm_, "[ Declaration");
   ASSERT(variable != NULL);  // Must have been resolved.
   Slot* slot = variable->AsSlot();
-  Property* prop = variable->AsProperty();
-
-  if (slot != NULL) {
-    switch (slot->type()) {
-      case Slot::PARAMETER:
-      case Slot::LOCAL:
-        if (mode == Variable::CONST) {
-          __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
-          __ movq(Operand(rbp, SlotOffset(slot)), kScratchRegister);
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ movq(Operand(rbp, SlotOffset(slot)), result_register());
-        }
-        break;
-
-      case Slot::CONTEXT:
-        // We bypass the general EmitSlotSearch because we know more about
-        // this specific context.
-
-        // The variable in the decl always resides in the current function
-        // context.
-        ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
-        if (FLAG_debug_code) {
-          // Check that we're not inside a with or catch context.
-          __ movq(rbx, FieldOperand(rsi, HeapObject::kMapOffset));
-          __ CompareRoot(rbx, Heap::kWithContextMapRootIndex);
-          __ Check(not_equal, "Declaration in with context.");
-          __ CompareRoot(rbx, Heap::kCatchContextMapRootIndex);
-          __ Check(not_equal, "Declaration in catch context.");
-        }
-        if (mode == Variable::CONST) {
-          __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
-          __ movq(ContextOperand(rsi, slot->index()), kScratchRegister);
-          // No write barrier since the hole value is in old space.
-        } else if (function != NULL) {
-          VisitForAccumulatorValue(function);
-          __ movq(ContextOperand(rsi, slot->index()), result_register());
-          int offset = Context::SlotOffset(slot->index());
-          __ movq(rbx, rsi);
-          __ RecordWrite(rbx, offset, result_register(), rcx);
-        }
-        break;
-
-      case Slot::LOOKUP: {
-        __ push(rsi);
-        __ Push(variable->name());
-        // Declaration nodes are always introduced in one of two modes.
-        ASSERT(mode == Variable::VAR || mode == Variable::CONST);
-        PropertyAttributes attr = (mode == Variable::VAR) ? NONE : READ_ONLY;
-        __ Push(Smi::FromInt(attr));
-        // Push initial value, if any.
-        // Note: For variables we must not push an initial value (such as
-        // 'undefined') because we may have a (legal) redeclaration and we
-        // must not destroy the current value.
-        if (mode == Variable::CONST) {
-          __ PushRoot(Heap::kTheHoleValueRootIndex);
-        } else if (function != NULL) {
-          VisitForStackValue(function);
-        } else {
-          __ Push(Smi::FromInt(0));  // no initial value!
-        }
-        __ CallRuntime(Runtime::kDeclareContextSlot, 4);
-        break;
+  ASSERT(slot != NULL);
+  switch (slot->type()) {
+    case Slot::PARAMETER:
+    case Slot::LOCAL:
+      if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ movq(Operand(rbp, SlotOffset(slot)), result_register());
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
+        __ movq(Operand(rbp, SlotOffset(slot)), kScratchRegister);
       }
-    }
+      break;
 
-  } else if (prop != NULL) {
-    // A const declaration aliasing a parameter is an illegal redeclaration.
-    ASSERT(mode != Variable::CONST);
-    if (function != NULL) {
-      // We are declaring a function that rewrites to a property.
-      // Use (keyed) IC to set the initial value.  We cannot visit the
-      // rewrite because it's shared and we risk recording duplicate AST
-      // IDs for bailouts from optimized code.
-      ASSERT(prop->obj()->AsVariableProxy() != NULL);
-      { AccumulatorValueContext for_object(this);
-        EmitVariableLoad(prop->obj()->AsVariableProxy());
+    case Slot::CONTEXT:
+      // We bypass the general EmitSlotSearch because we know more about
+      // this specific context.
+
+      // The variable in the decl always resides in the current function
+      // context.
+      ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
+      if (FLAG_debug_code) {
+        // Check that we're not inside a with or catch context.
+        __ movq(rbx, FieldOperand(rsi, HeapObject::kMapOffset));
+        __ CompareRoot(rbx, Heap::kWithContextMapRootIndex);
+        __ Check(not_equal, "Declaration in with context.");
+        __ CompareRoot(rbx, Heap::kCatchContextMapRootIndex);
+        __ Check(not_equal, "Declaration in catch context.");
       }
-      __ push(rax);
-      VisitForAccumulatorValue(function);
-      __ pop(rdx);
-      ASSERT(prop->key()->AsLiteral() != NULL &&
-             prop->key()->AsLiteral()->handle()->IsSmi());
-      __ Move(rcx, prop->key()->AsLiteral()->handle());
+      if (function != NULL) {
+        VisitForAccumulatorValue(function);
+        __ movq(ContextOperand(rsi, slot->index()), result_register());
+        int offset = Context::SlotOffset(slot->index());
+        __ movq(rbx, rsi);
+        __ RecordWrite(rbx, offset, result_register(), rcx);
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
+        __ movq(ContextOperand(rsi, slot->index()), kScratchRegister);
+        // No write barrier since the hole value is in old space.
+      }
+      break;
 
-      Handle<Code> ic = is_strict_mode()
-          ? isolate()->builtins()->KeyedStoreIC_Initialize_Strict()
-          : isolate()->builtins()->KeyedStoreIC_Initialize();
-      __ call(ic);
+    case Slot::LOOKUP: {
+      __ push(rsi);
+      __ Push(variable->name());
+      // Declaration nodes are always introduced in one of two modes.
+      ASSERT(mode == Variable::VAR ||
+             mode == Variable::CONST ||
+             mode == Variable::LET);
+      PropertyAttributes attr = (mode == Variable::CONST) ? READ_ONLY : NONE;
+      __ Push(Smi::FromInt(attr));
+      // Push initial value, if any.
+      // Note: For variables we must not push an initial value (such as
+      // 'undefined') because we may have a (legal) redeclaration and we
+      // must not destroy the current value.
+      if (function != NULL) {
+        VisitForStackValue(function);
+      } else if (mode == Variable::CONST || mode == Variable::LET) {
+        __ PushRoot(Heap::kTheHoleValueRootIndex);
+      } else {
+        __ Push(Smi::FromInt(0));  // no initial value!
+      }
+      __ CallRuntime(Runtime::kDeclareContextSlot, 4);
+      break;
     }
   }
 }
@@ -840,7 +813,7 @@
   __ bind(&next_test);
   __ Drop(1);  // Switch value is no longer needed.
   if (default_clause == NULL) {
-    __ jmp(nested_statement.break_target());
+    __ jmp(nested_statement.break_label());
   } else {
     __ jmp(default_clause->body_target());
   }
@@ -854,7 +827,7 @@
     VisitStatements(clause->statements());
   }
 
-  __ bind(nested_statement.break_target());
+  __ bind(nested_statement.break_label());
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
 }
 
@@ -980,7 +953,7 @@
   __ bind(&loop);
   __ movq(rax, Operand(rsp, 0 * kPointerSize));  // Get the current index.
   __ cmpq(rax, Operand(rsp, 1 * kPointerSize));  // Compare to the array length.
-  __ j(above_equal, loop_statement.break_target());
+  __ j(above_equal, loop_statement.break_label());
 
   // Get the current entry of the array into register rbx.
   __ movq(rbx, Operand(rsp, 2 * kPointerSize));
@@ -1008,7 +981,7 @@
   __ push(rbx);  // Current entry.
   __ InvokeBuiltin(Builtins::FILTER_KEY, CALL_FUNCTION);
   __ Cmp(rax, Smi::FromInt(0));
-  __ j(equal, loop_statement.continue_target());
+  __ j(equal, loop_statement.continue_label());
   __ movq(rbx, rax);
 
   // Update the 'each' property or variable from the possibly filtered
@@ -1025,14 +998,14 @@
 
   // Generate code for going to the next element by incrementing the
   // index (smi) stored on top of the stack.
-  __ bind(loop_statement.continue_target());
+  __ bind(loop_statement.continue_label());
   __ SmiAddConstant(Operand(rsp, 0 * kPointerSize), Smi::FromInt(1));
 
   EmitStackCheck(stmt);
   __ jmp(&loop);
 
   // Remove the pointers stored on the stack.
-  __ bind(loop_statement.break_target());
+  __ bind(loop_statement.break_label());
   __ addq(rsp, Immediate(5 * kPointerSize));
 
   // Exit and decrement the loop depth.
@@ -1273,6 +1246,18 @@
       __ LoadRoot(rax, Heap::kUndefinedValueRootIndex);
       __ bind(&done);
       context()->Plug(rax);
+    } else if (var->mode() == Variable::LET) {
+      // Let bindings may be the hole value if they have not been initialized.
+      // Throw a type error in this case.
+      Label done;
+      MemOperand slot_operand = EmitSlotSearch(slot, rax);
+      __ movq(rax, slot_operand);
+      __ CompareRoot(rax, Heap::kTheHoleValueRootIndex);
+      __ j(not_equal, &done, Label::kNear);
+      __ Push(var->name());
+      __ CallRuntime(Runtime::kThrowReferenceError, 1);
+      __ bind(&done);
+      context()->Plug(rax);
     } else {
       context()->Plug(slot);
     }
@@ -1802,6 +1787,57 @@
     }
     __ bind(&skip);
 
+  } else if (var->mode() == Variable::LET && op != Token::INIT_LET) {
+    // Perform the assignment for non-const variables.  Const assignments
+    // are simply skipped.
+    Slot* slot = var->AsSlot();
+    switch (slot->type()) {
+      case Slot::PARAMETER:
+      case Slot::LOCAL: {
+        Label assign;
+        // Check for an initialized let binding.
+        __ movq(rdx, Operand(rbp, SlotOffset(slot)));
+        __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
+        __ j(not_equal, &assign);
+        __ Push(var->name());
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+        // Perform the assignment.
+        __ bind(&assign);
+        __ movq(Operand(rbp, SlotOffset(slot)), rax);
+        break;
+      }
+
+      case Slot::CONTEXT: {
+        // Let variables may be the hole value if they have not been
+        // initialized. Throw a type error in this case.
+        Label assign;
+        MemOperand target = EmitSlotSearch(slot, rcx);
+        // Check for an initialized let binding.
+        __ movq(rdx, target);
+        __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
+        __ j(not_equal, &assign, Label::kNear);
+        __ Push(var->name());
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+        // Perform the assignment.
+        __ bind(&assign);
+        __ movq(target, rax);
+        // The value of the assignment is in eax. RecordWrite clobbers its
+        // register arguments.
+        __ movq(rdx, rax);
+        int offset = Context::SlotOffset(slot->index());
+        __ RecordWrite(rcx, offset, rdx, rbx);
+        break;
+      }
+
+      case Slot::LOOKUP:
+        // Call the runtime for the assignment.
+        __ push(rax);  // Value.
+        __ push(rsi);  // Context.
+        __ Push(var->name());
+        __ Push(Smi::FromInt(strict_mode_flag()));
+        __ CallRuntime(Runtime::kStoreContextSlot, 4);
+        break;
+    }
   } else if (var->mode() != Variable::CONST) {
     // Perform the assignment for non-const variables.  Const assignments
     // are simply skipped.
@@ -2167,38 +2203,10 @@
       EmitCallWithIC(expr, key->handle(), RelocInfo::CODE_TARGET);
     } else {
       // Call to a keyed property.
-      // For a synthetic property use keyed load IC followed by function call,
-      // for a regular property use EmitKeyedCallWithIC.
-      if (prop->is_synthetic()) {
-        // Do not visit the object and key subexpressions (they are shared
-        // by all occurrences of the same rewritten parameter).
-        ASSERT(prop->obj()->AsVariableProxy() != NULL);
-        ASSERT(prop->obj()->AsVariableProxy()->var()->AsSlot() != NULL);
-        Slot* slot = prop->obj()->AsVariableProxy()->var()->AsSlot();
-        MemOperand operand = EmitSlotSearch(slot, rdx);
-        __ movq(rdx, operand);
-
-        ASSERT(prop->key()->AsLiteral() != NULL);
-        ASSERT(prop->key()->AsLiteral()->handle()->IsSmi());
-        __ Move(rax, prop->key()->AsLiteral()->handle());
-
-        // Record source code position for IC call.
-        SetSourcePosition(prop->position());
-
-        Handle<Code> ic = isolate()->builtins()->KeyedLoadIC_Initialize();
-        __ call(ic, RelocInfo::CODE_TARGET, GetPropertyId(prop));
-        // Push result (function).
-        __ push(rax);
-        // Push Global receiver.
-        __ movq(rcx, GlobalObjectOperand());
-        __ push(FieldOperand(rcx, GlobalObject::kGlobalReceiverOffset));
-        EmitCallWithStub(expr, NO_CALL_FUNCTION_FLAGS);
-      } else {
-        { PreservePositionScope scope(masm()->positions_recorder());
-          VisitForStackValue(prop->obj());
-        }
-        EmitKeyedCallWithIC(expr, prop->key());
+      { PreservePositionScope scope(masm()->positions_recorder());
+        VisitForStackValue(prop->obj());
       }
+      EmitKeyedCallWithIC(expr, prop->key());
     }
   } else {
     { PreservePositionScope scope(masm()->positions_recorder());
@@ -3130,7 +3138,7 @@
 
   Label done, not_found;
   // tmp now holds finger offset as a smi.
-  ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
   __ movq(tmp, FieldOperand(cache, JSFunctionResultCache::kFingerOffset));
   SmiIndex index =
       __ SmiToIndex(kScratchRegister, tmp, kPointerSizeLog2);
@@ -3516,39 +3524,6 @@
 }
 
 
-void FullCodeGenerator::EmitIsNativeOrStrictMode(ZoneList<Expression*>* args) {
-  ASSERT(args->length() == 1);
-
-  // Load the function into rax.
-  VisitForAccumulatorValue(args->at(0));
-
-  // Prepare for the test.
-  Label materialize_true, materialize_false;
-  Label* if_true = NULL;
-  Label* if_false = NULL;
-  Label* fall_through = NULL;
-  context()->PrepareTest(&materialize_true, &materialize_false,
-                         &if_true, &if_false, &fall_through);
-
-  // Test for strict mode function.
-  __ movq(rdx, FieldOperand(rax, JSFunction::kSharedFunctionInfoOffset));
-  __ testb(FieldOperand(rdx, SharedFunctionInfo::kStrictModeByteOffset),
-           Immediate(1 << SharedFunctionInfo::kStrictModeBitWithinByte));
-  __ j(not_equal, if_true);
-
-  // Test for native function.
-  __ testb(FieldOperand(rdx, SharedFunctionInfo::kNativeByteOffset),
-           Immediate(1 << SharedFunctionInfo::kNativeBitWithinByte));
-  __ j(not_equal, if_true);
-
-  // Not native or strict-mode function.
-  __ jmp(if_false);
-
-  PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
-  context()->Plug(if_true, if_false);
-}
-
-
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   Handle<String> name = expr->name();
   if (name->length() > 0 && name->Get(0) == '_') {
@@ -3597,17 +3572,11 @@
       Variable* var = expr->expression()->AsVariableProxy()->AsVariable();
 
       if (prop != NULL) {
-        if (prop->is_synthetic()) {
-          // Result of deleting parameters is false, even when they rewrite
-          // to accesses on the arguments object.
-          context()->Plug(false);
-        } else {
-          VisitForStackValue(prop->obj());
-          VisitForStackValue(prop->key());
-          __ Push(Smi::FromInt(strict_mode_flag()));
-          __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
-          context()->Plug(rax);
-        }
+        VisitForStackValue(prop->obj());
+        VisitForStackValue(prop->key());
+        __ Push(Smi::FromInt(strict_mode_flag()));
+        __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
+        context()->Plug(rax);
       } else if (var != NULL) {
         // Delete of an unqualified identifier is disallowed in strict mode
         // but "delete this" is.
@@ -3971,6 +3940,10 @@
     __ j(equal, if_true);
     __ CompareRoot(rax, Heap::kFalseValueRootIndex);
     Split(equal, if_true, if_false, fall_through);
+  } else if (FLAG_harmony_typeof &&
+             check->Equals(isolate()->heap()->null_symbol())) {
+    __ CompareRoot(rax, Heap::kNullValueRootIndex);
+    Split(equal, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->undefined_symbol())) {
     __ CompareRoot(rax, Heap::kUndefinedValueRootIndex);
     __ j(equal, if_true);
@@ -3987,8 +3960,10 @@
     Split(above_equal, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->object_symbol())) {
     __ JumpIfSmi(rax, if_false);
-    __ CompareRoot(rax, Heap::kNullValueRootIndex);
-    __ j(equal, if_true);
+    if (!FLAG_harmony_typeof) {
+      __ CompareRoot(rax, Heap::kNullValueRootIndex);
+      __ j(equal, if_true);
+    }
     __ CmpObjectType(rax, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, rdx);
     __ j(below, if_false);
     __ CmpInstanceType(rdx, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
@@ -4231,6 +4206,33 @@
 
 #undef __
 
+#define __ ACCESS_MASM(masm())
+
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
+    int* stack_depth,
+    int* context_length) {
+  // The macros used here must preserve the result register.
+
+  // Because the handler block contains the context of the finally
+  // code, we can restore it directly from there for the finally code
+  // rather than iteratively unwinding contexts via their previous
+  // links.
+  __ Drop(*stack_depth);  // Down to the handler block.
+  if (*context_length > 0) {
+    // Restore the context to its dedicated register and the stack.
+    __ movq(rsi, Operand(rsp, StackHandlerConstants::kContextOffset));
+    __ movq(Operand(rbp, StandardFrameConstants::kContextOffset), rsi);
+  }
+  __ PopTryHandler();
+  __ call(finally_entry_);
+
+  *stack_depth = 0;
+  *context_length = 0;
+  return previous_;
+}
+
+
+#undef __
 
 } }  // namespace v8::internal
 
diff --git a/src/x64/ic-x64.cc b/src/x64/ic-x64.cc
index 339d2c1..990c171 100644
--- a/src/x64/ic-x64.cc
+++ b/src/x64/ic-x64.cc
@@ -378,7 +378,7 @@
   __ j(zero, index_string);  // The value in hash is used at jump target.
 
   // Is the string a symbol?
-  ASSERT(kSymbolTag != 0);
+  STATIC_ASSERT(kSymbolTag != 0);
   __ testb(FieldOperand(map, Map::kInstanceTypeOffset),
            Immediate(kIsSymbolMask));
   __ j(zero, not_symbol);
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index e505058..c182413 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1216,17 +1216,10 @@
 }
 
 
-void LCodeGen::DoFixedArrayLength(LFixedArrayLength* instr) {
+void LCodeGen::DoFixedArrayBaseLength(LFixedArrayBaseLength* instr) {
   Register result = ToRegister(instr->result());
   Register array = ToRegister(instr->InputAt(0));
-  __ movq(result, FieldOperand(array, FixedArray::kLengthOffset));
-}
-
-
-void LCodeGen::DoExternalArrayLength(LExternalArrayLength* instr) {
-  Register result = ToRegister(instr->result());
-  Register array = ToRegister(instr->InputAt(0));
-  __ movl(result, FieldOperand(array, ExternalPixelArray::kLengthOffset));
+  __ movq(result, FieldOperand(array, FixedArrayBase::kLengthOffset));
 }
 
 
@@ -1402,39 +1395,83 @@
       Label* true_label = chunk_->GetAssemblyLabel(true_block);
       Label* false_label = chunk_->GetAssemblyLabel(false_block);
 
-      __ CompareRoot(reg, Heap::kUndefinedValueRootIndex);
-      __ j(equal, false_label);
-      __ CompareRoot(reg, Heap::kTrueValueRootIndex);
-      __ j(equal, true_label);
-      __ CompareRoot(reg, Heap::kFalseValueRootIndex);
-      __ j(equal, false_label);
-      __ Cmp(reg, Smi::FromInt(0));
-      __ j(equal, false_label);
-      __ JumpIfSmi(reg, true_label);
+      ToBooleanStub::Types expected = instr->hydrogen()->expected_input_types();
+      // Avoid deopts in the case where we've never executed this path before.
+      if (expected.IsEmpty()) expected = ToBooleanStub::all_types();
 
-      // Test for double values. Plus/minus zero and NaN are false.
-      Label call_stub;
-      __ CompareRoot(FieldOperand(reg, HeapObject::kMapOffset),
-                     Heap::kHeapNumberMapRootIndex);
-      __ j(not_equal, &call_stub, Label::kNear);
+      if (expected.Contains(ToBooleanStub::UNDEFINED)) {
+        // undefined -> false.
+        __ CompareRoot(reg, Heap::kUndefinedValueRootIndex);
+        __ j(equal, false_label);
+      }
+      if (expected.Contains(ToBooleanStub::BOOLEAN)) {
+        // true -> true.
+        __ CompareRoot(reg, Heap::kTrueValueRootIndex);
+        __ j(equal, true_label);
+        // false -> false.
+        __ CompareRoot(reg, Heap::kFalseValueRootIndex);
+        __ j(equal, false_label);
+      }
+      if (expected.Contains(ToBooleanStub::NULL_TYPE)) {
+        // 'null' -> false.
+        __ CompareRoot(reg, Heap::kNullValueRootIndex);
+        __ j(equal, false_label);
+      }
 
-      // HeapNumber => false iff +0, -0, or NaN. These three cases set the
-      // zero flag when compared to zero using ucomisd.
-      __ xorps(xmm0, xmm0);
-      __ ucomisd(xmm0, FieldOperand(reg, HeapNumber::kValueOffset));
-      __ j(zero, false_label);
-      __ jmp(true_label);
+      if (expected.Contains(ToBooleanStub::SMI)) {
+        // Smis: 0 -> false, all other -> true.
+        __ Cmp(reg, Smi::FromInt(0));
+        __ j(equal, false_label);
+        __ JumpIfSmi(reg, true_label);
+      } else if (expected.NeedsMap()) {
+        // If we need a map later and have a Smi -> deopt.
+        __ testb(reg, Immediate(kSmiTagMask));
+        DeoptimizeIf(zero, instr->environment());
+      }
 
-      // The conversion stub doesn't cause garbage collections so it's
-      // safe to not record a safepoint after the call.
-      __ bind(&call_stub);
-      ToBooleanStub stub(rax);
-      __ Pushad();
-      __ push(reg);
-      __ CallStub(&stub);
-      __ testq(rax, rax);
-      __ Popad();
-      EmitBranch(true_block, false_block, not_zero);
+      const Register map = kScratchRegister;
+      if (expected.NeedsMap()) {
+        __ movq(map, FieldOperand(reg, HeapObject::kMapOffset));
+
+        if (expected.CanBeUndetectable()) {
+          // Undetectable -> false.
+          __ testb(FieldOperand(map, Map::kBitFieldOffset),
+                   Immediate(1 << Map::kIsUndetectable));
+          __ j(not_zero, false_label);
+        }
+      }
+
+      if (expected.Contains(ToBooleanStub::SPEC_OBJECT)) {
+        // spec object -> true.
+        __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
+        __ j(above_equal, true_label);
+      }
+
+      if (expected.Contains(ToBooleanStub::STRING)) {
+        // String value -> false iff empty.
+        Label not_string;
+        __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
+        __ j(above_equal, &not_string, Label::kNear);
+        __ cmpq(FieldOperand(reg, String::kLengthOffset), Immediate(0));
+        __ j(not_zero, true_label);
+        __ jmp(false_label);
+        __ bind(&not_string);
+      }
+
+      if (expected.Contains(ToBooleanStub::HEAP_NUMBER)) {
+        // heap number -> false iff +0, -0, or NaN.
+        Label not_heap_number;
+        __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
+        __ j(not_equal, &not_heap_number, Label::kNear);
+        __ xorps(xmm0, xmm0);
+        __ ucomisd(xmm0, FieldOperand(reg, HeapNumber::kValueOffset));
+        __ j(zero, false_label);
+        __ jmp(true_label);
+        __ bind(&not_heap_number);
+      }
+
+      // We've seen something for the first time -> deopt.
+      DeoptimizeIf(no_condition, instr->environment());
     }
   }
 }
@@ -2225,16 +2262,13 @@
 
 
 void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
-  Register elements = ToRegister(instr->elements());
-  Register key = ToRegister(instr->key());
   Register result = ToRegister(instr->result());
-  ASSERT(result.is(elements));
 
   // Load the result.
-  __ movq(result, FieldOperand(elements,
-                               key,
-                               times_pointer_size,
-                               FixedArray::kHeaderSize));
+  __ movq(result,
+          BuildFastArrayOperand(instr->elements(), instr->key(),
+                                JSObject::FAST_ELEMENTS,
+                                FixedArray::kHeaderSize - kHeapObjectTag));
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
@@ -2268,22 +2302,22 @@
 
 
 Operand LCodeGen::BuildFastArrayOperand(
-    LOperand* external_pointer,
+    LOperand* elements_pointer,
     LOperand* key,
     JSObject::ElementsKind elements_kind,
     uint32_t offset) {
-  Register external_pointer_reg = ToRegister(external_pointer);
+  Register elements_pointer_reg = ToRegister(elements_pointer);
   int shift_size = ElementsKindToShiftSize(elements_kind);
   if (key->IsConstantOperand()) {
     int constant_value = ToInteger32(LConstantOperand::cast(key));
     if (constant_value & 0xF0000000) {
       Abort("array index constant value too big");
     }
-    return Operand(external_pointer_reg,
+    return Operand(elements_pointer_reg,
                    constant_value * (1 << shift_size) + offset);
   } else {
     ScaleFactor scale_factor = static_cast<ScaleFactor>(shift_size);
-    return Operand(external_pointer_reg, ToRegister(key),
+    return Operand(elements_pointer_reg, ToRegister(key),
                    scale_factor, offset);
   }
 }
@@ -2679,6 +2713,7 @@
   XMMRegister xmm_scratch = xmm0;
   Register output_reg = ToRegister(instr->result());
   XMMRegister input_reg = ToDoubleRegister(instr->InputAt(0));
+  Label done;
 
   if (CpuFeatures::IsSupported(SSE4_1)) {
     CpuFeatures::Scope scope(SSE4_1);
@@ -2693,13 +2728,20 @@
     __ cmpl(output_reg, Immediate(0x80000000));
     DeoptimizeIf(equal, instr->environment());
   } else {
+    // Deoptimize on negative inputs.
     __ xorps(xmm_scratch, xmm_scratch);  // Zero the register.
     __ ucomisd(input_reg, xmm_scratch);
-
+    DeoptimizeIf(below, instr->environment());
     if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
-      DeoptimizeIf(below_equal, instr->environment());
-    } else {
-      DeoptimizeIf(below, instr->environment());
+      // Check for negative zero.
+      Label positive_sign;
+      __ j(above, &positive_sign, Label::kNear);
+      __ movmskpd(output_reg, input_reg);
+      __ testq(output_reg, Immediate(1));
+      DeoptimizeIf(not_zero, instr->environment());
+      __ Set(output_reg, 0);
+      __ jmp(&done);
+      __ bind(&positive_sign);
     }
 
     // Use truncating instruction (OK because input is positive).
@@ -2709,6 +2751,7 @@
     __ cmpl(output_reg, Immediate(0x80000000));
     DeoptimizeIf(equal, instr->environment());
   }
+  __ bind(&done);
 }
 
 
@@ -3057,12 +3100,22 @@
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  if (instr->length()->IsRegister()) {
-    __ cmpq(ToRegister(instr->index()), ToRegister(instr->length()));
+  if (instr->index()->IsConstantOperand()) {
+    if (instr->length()->IsRegister()) {
+      __ cmpq(ToRegister(instr->length()),
+              Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
+    } else {
+      __ cmpq(ToOperand(instr->length()),
+              Immediate(ToInteger32(LConstantOperand::cast(instr->index()))));
+    }
   } else {
-    __ cmpq(ToRegister(instr->index()), ToOperand(instr->length()));
+    if (instr->length()->IsRegister()) {
+      __ cmpq(ToRegister(instr->length()), ToRegister(instr->index()));
+    } else {
+      __ cmpq(ToOperand(instr->length()), ToRegister(instr->index()));
+    }
   }
-  DeoptimizeIf(above_equal, instr->environment());
+  DeoptimizeIf(below_equal, instr->environment());
 }
 
 
@@ -3105,8 +3158,6 @@
   __ ucomisd(value, value);
   __ j(parity_odd, &have_value);  // NaN.
 
-  ExternalReference canonical_nan_reference =
-      ExternalReference::address_of_canonical_non_hole_nan();
   __ Set(kScratchRegister, BitCast<uint64_t>(
       FixedDoubleArray::canonical_not_the_hole_nan_as_double()));
   __ movq(value, kScratchRegister);
@@ -3149,95 +3200,78 @@
   };
 
   Register string = ToRegister(instr->string());
-  Register index = no_reg;
-  int const_index = -1;
-  if (instr->index()->IsConstantOperand()) {
-    const_index = ToInteger32(LConstantOperand::cast(instr->index()));
-    STATIC_ASSERT(String::kMaxLength <= Smi::kMaxValue);
-    if (!Smi::IsValid(const_index)) {
-      // Guaranteed to be out of bounds because of the assert above.
-      // So the bounds check that must dominate this instruction must
-      // have deoptimized already.
-      if (FLAG_debug_code) {
-        __ Abort("StringCharCodeAt: out of bounds index.");
-      }
-      // No code needs to be generated.
-      return;
-    }
-  } else {
-    index = ToRegister(instr->index());
-  }
+  Register index = ToRegister(instr->index());
   Register result = ToRegister(instr->result());
 
   DeferredStringCharCodeAt* deferred =
       new DeferredStringCharCodeAt(this, instr);
 
-  Label flat_string, ascii_string, done;
-
   // Fetch the instance type of the receiver into result register.
   __ movq(result, FieldOperand(string, HeapObject::kMapOffset));
   __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset));
 
-  // We need special handling for non-sequential strings.
-  STATIC_ASSERT(kSeqStringTag == 0);
-  __ testb(result, Immediate(kStringRepresentationMask));
-  __ j(zero, &flat_string, Label::kNear);
+  // We need special handling for indirect strings.
+  Label check_sequential;
+  __ testb(result, Immediate(kIsIndirectStringMask));
+  __ j(zero, &check_sequential, Label::kNear);
 
-  // Handle cons strings and go to deferred code for the rest.
-  __ testb(result, Immediate(kIsConsStringMask));
-  __ j(zero, deferred->entry());
+  // Dispatch on the indirect string shape: slice or cons.
+  Label cons_string;
+  __ testb(result, Immediate(kSlicedNotConsMask));
+  __ j(zero, &cons_string, Label::kNear);
 
-  // ConsString.
+  // Handle slices.
+  Label indirect_string_loaded;
+  __ SmiToInteger32(result, FieldOperand(string, SlicedString::kOffsetOffset));
+  __ addq(index, result);
+  __ movq(string, FieldOperand(string, SlicedString::kParentOffset));
+  __ jmp(&indirect_string_loaded, Label::kNear);
+
+  // Handle conses.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
+  __ bind(&cons_string);
   __ CompareRoot(FieldOperand(string, ConsString::kSecondOffset),
                  Heap::kEmptyStringRootIndex);
   __ j(not_equal, deferred->entry());
-  // Get the first of the two strings and load its instance type.
   __ movq(string, FieldOperand(string, ConsString::kFirstOffset));
+
+  __ bind(&indirect_string_loaded);
   __ movq(result, FieldOperand(string, HeapObject::kMapOffset));
   __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset));
-  // If the first cons component is also non-flat, then go to runtime.
+
+  // Check whether the string is sequential. The only non-sequential
+  // shapes we support have just been unwrapped above.
+  __ bind(&check_sequential);
   STATIC_ASSERT(kSeqStringTag == 0);
   __ testb(result, Immediate(kStringRepresentationMask));
   __ j(not_zero, deferred->entry());
 
-  // Check for ASCII or two-byte string.
-  __ bind(&flat_string);
+  // Dispatch on the encoding: ASCII or two-byte.
+  Label ascii_string;
   STATIC_ASSERT(kAsciiStringTag != 0);
   __ testb(result, Immediate(kStringEncodingMask));
   __ j(not_zero, &ascii_string, Label::kNear);
 
   // Two-byte string.
   // Load the two-byte character code into the result register.
+  Label done;
   STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
-  if (instr->index()->IsConstantOperand()) {
-    __ movzxwl(result,
-               FieldOperand(string,
-                            SeqTwoByteString::kHeaderSize +
-                            (kUC16Size * const_index)));
-  } else {
-    __ movzxwl(result, FieldOperand(string,
-                                    index,
-                                    times_2,
-                                    SeqTwoByteString::kHeaderSize));
-  }
+  __ movzxwl(result, FieldOperand(string,
+                                  index,
+                                  times_2,
+                                  SeqTwoByteString::kHeaderSize));
   __ jmp(&done, Label::kNear);
 
   // ASCII string.
   // Load the byte into the result register.
   __ bind(&ascii_string);
-  if (instr->index()->IsConstantOperand()) {
-    __ movzxbl(result, FieldOperand(string,
-                                    SeqAsciiString::kHeaderSize + const_index));
-  } else {
-    __ movzxbl(result, FieldOperand(string,
-                                    index,
-                                    times_1,
-                                    SeqAsciiString::kHeaderSize));
-  }
+  __ movzxbl(result, FieldOperand(string,
+                                  index,
+                                  times_1,
+                                  SeqAsciiString::kHeaderSize));
   __ bind(&done);
   __ bind(deferred->exit());
 }
@@ -3930,6 +3964,10 @@
     __ CompareRoot(input, Heap::kFalseValueRootIndex);
     final_branch_condition = equal;
 
+  } else if (FLAG_harmony_typeof && type_name->Equals(heap()->null_symbol())) {
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
+    final_branch_condition = equal;
+
   } else if (type_name->Equals(heap()->undefined_symbol())) {
     __ CompareRoot(input, Heap::kUndefinedValueRootIndex);
     __ j(equal, true_label);
@@ -3947,8 +3985,10 @@
 
   } else if (type_name->Equals(heap()->object_symbol())) {
     __ JumpIfSmi(input, false_label);
-    __ CompareRoot(input, Heap::kNullValueRootIndex);
-    __ j(equal, true_label);
+    if (!FLAG_harmony_typeof) {
+      __ CompareRoot(input, Heap::kNullValueRootIndex);
+      __ j(equal, true_label);
+    }
     __ CmpObjectType(input, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, input);
     __ j(below, false_label);
     __ CmpInstanceType(input, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
diff --git a/src/x64/lithium-codegen-x64.h b/src/x64/lithium-codegen-x64.h
index d7c72b5..0622e9d 100644
--- a/src/x64/lithium-codegen-x64.h
+++ b/src/x64/lithium-codegen-x64.h
@@ -216,7 +216,7 @@
   Register ToRegister(int index) const;
   XMMRegister ToDoubleRegister(int index) const;
   Operand BuildFastArrayOperand(
-      LOperand* external_pointer,
+      LOperand* elements_pointer,
       LOperand* key,
       JSObject::ElementsKind elements_kind,
       uint32_t offset);
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 00b906d..9dc925d 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1040,7 +1040,7 @@
         : instr->SecondSuccessor();
     return new LGoto(successor->block_id());
   }
-  return new LBranch(UseRegisterAtStart(v));
+  return AssignEnvironment(new LBranch(UseRegister(v)));
 }
 
 
@@ -1502,16 +1502,10 @@
 }
 
 
-LInstruction* LChunkBuilder::DoFixedArrayLength(HFixedArrayLength* instr) {
+LInstruction* LChunkBuilder::DoFixedArrayBaseLength(
+    HFixedArrayBaseLength* instr) {
   LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LFixedArrayLength(array));
-}
-
-
-LInstruction* LChunkBuilder::DoExternalArrayLength(
-    HExternalArrayLength* instr) {
-  LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LExternalArrayLength(array));
+  return DefineAsRegister(new LFixedArrayBaseLength(array));
 }
 
 
@@ -1529,8 +1523,9 @@
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
-  return AssignEnvironment(new LBoundsCheck(UseRegisterAtStart(instr->index()),
-                                            Use(instr->length())));
+  return AssignEnvironment(new LBoundsCheck(
+      UseRegisterOrConstantAtStart(instr->index()),
+      Use(instr->length())));
 }
 
 
@@ -1829,9 +1824,9 @@
   ASSERT(instr->representation().IsTagged());
   ASSERT(instr->key()->representation().IsInteger32());
   LOperand* obj = UseRegisterAtStart(instr->object());
-  LOperand* key = UseRegisterAtStart(instr->key());
+  LOperand* key = UseRegisterOrConstantAtStart(instr->key());
   LLoadKeyedFastElement* result = new LLoadKeyedFastElement(obj, key);
-  return AssignEnvironment(DefineSameAsFirst(result));
+  return AssignEnvironment(DefineAsRegister(result));
 }
 
 
@@ -1993,8 +1988,8 @@
 
 
 LInstruction* LChunkBuilder::DoStringCharCodeAt(HStringCharCodeAt* instr) {
-  LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegisterOrConstant(instr->index());
+  LOperand* string = UseTempRegister(instr->string());
+  LOperand* index = UseTempRegister(instr->index());
   LStringCharCodeAt* result = new LStringCharCodeAt(string, index);
   return AssignEnvironment(AssignPointerMap(DefineAsRegister(result)));
 }
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 18a036f..05b6637 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -92,8 +92,7 @@
   V(DivI)                                       \
   V(DoubleToI)                                  \
   V(ElementsKind)                               \
-  V(ExternalArrayLength)                        \
-  V(FixedArrayLength)                           \
+  V(FixedArrayBaseLength)                       \
   V(FunctionLiteral)                            \
   V(GetCachedArrayIndex)                        \
   V(GlobalObject)                               \
@@ -913,25 +912,15 @@
 };
 
 
-class LExternalArrayLength: public LTemplateInstruction<1, 1, 0> {
+class LFixedArrayBaseLength: public LTemplateInstruction<1, 1, 0> {
  public:
-  explicit LExternalArrayLength(LOperand* value) {
+  explicit LFixedArrayBaseLength(LOperand* value) {
     inputs_[0] = value;
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(ExternalArrayLength, "external-array-length")
-  DECLARE_HYDROGEN_ACCESSOR(ExternalArrayLength)
-};
-
-
-class LFixedArrayLength: public LTemplateInstruction<1, 1, 0> {
- public:
-  explicit LFixedArrayLength(LOperand* value) {
-    inputs_[0] = value;
-  }
-
-  DECLARE_CONCRETE_INSTRUCTION(FixedArrayLength, "fixed-array-length")
-  DECLARE_HYDROGEN_ACCESSOR(FixedArrayLength)
+  DECLARE_CONCRETE_INSTRUCTION(FixedArrayBaseLength,
+                               "fixed-array-base-length")
+  DECLARE_HYDROGEN_ACCESSOR(FixedArrayBaseLength)
 };
 
 
@@ -2135,14 +2124,18 @@
   template<int I, int T>
       LInstruction* DefineFixedDouble(LTemplateInstruction<1, I, T>* instr,
                                       XMMRegister reg);
+  // Assigns an environment to an instruction.  An instruction which can
+  // deoptimize must have an environment.
   LInstruction* AssignEnvironment(LInstruction* instr);
+  // Assigns a pointer map to an instruction.  An instruction which can
+  // trigger a GC or a lazy deoptimization must have a pointer map.
   LInstruction* AssignPointerMap(LInstruction* instr);
 
   enum CanDeoptimize { CAN_DEOPTIMIZE_EAGERLY, CANNOT_DEOPTIMIZE_EAGERLY };
 
-  // By default we assume that instruction sequences generated for calls
-  // cannot deoptimize eagerly and we do not attach environment to this
-  // instruction.
+  // Marks a call for the register allocator.  Assigns a pointer map to
+  // support GC and lazy deoptimization.  Assigns an environment to support
+  // eager deoptimization if CAN_DEOPTIMIZE_EAGERLY.
   LInstruction* MarkAsCall(
       LInstruction* instr,
       HInstruction* hinstr,
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 2b15553..b51d531 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -923,7 +923,7 @@
 
 
 void MacroAssembler::Integer32ToSmi(Register dst, Register src) {
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   if (!dst.is(src)) {
     movl(dst, src);
   }
@@ -961,7 +961,7 @@
 
 
 void MacroAssembler::SmiToInteger32(Register dst, Register src) {
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   if (!dst.is(src)) {
     movq(dst, src);
   }
@@ -975,7 +975,7 @@
 
 
 void MacroAssembler::SmiToInteger64(Register dst, Register src) {
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   if (!dst.is(src)) {
     movq(dst, src);
   }
@@ -1111,21 +1111,21 @@
 
 
 Condition MacroAssembler::CheckSmi(Register src) {
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   testb(src, Immediate(kSmiTagMask));
   return zero;
 }
 
 
 Condition MacroAssembler::CheckSmi(const Operand& src) {
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   testb(src, Immediate(kSmiTagMask));
   return zero;
 }
 
 
 Condition MacroAssembler::CheckNonNegativeSmi(Register src) {
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   // Test that both bits of the mask 0x8000000000000001 are zero.
   movq(kScratchRegister, src);
   rol(kScratchRegister, Immediate(1));
@@ -1138,7 +1138,7 @@
   if (first.is(second)) {
     return CheckSmi(first);
   }
-  ASSERT(kSmiTag == 0 && kHeapObjectTag == 1 && kHeapObjectTagMask == 3);
+  STATIC_ASSERT(kSmiTag == 0 && kHeapObjectTag == 1 && kHeapObjectTagMask == 3);
   leal(kScratchRegister, Operand(first, second, times_1, 0));
   testb(kScratchRegister, Immediate(0x03));
   return zero;
@@ -1294,7 +1294,7 @@
                                        Label::Distance near_jump) {
   // Does not assume that src is a smi.
   ASSERT_EQ(static_cast<int>(1), static_cast<int>(kSmiTagMask));
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   ASSERT(!dst.is(kScratchRegister));
   ASSERT(!src.is(kScratchRegister));
 
@@ -1998,7 +1998,7 @@
     Check(not_both_smis, "Both registers were smis in SelectNonSmi.");
   }
 #endif
-  ASSERT_EQ(0, kSmiTag);
+  STATIC_ASSERT(kSmiTag == 0);
   ASSERT_EQ(0, Smi::FromInt(0));
   movl(kScratchRegister, Immediate(kSmiTagMask));
   and_(kScratchRegister, src1);
@@ -2387,18 +2387,15 @@
 void MacroAssembler::PushTryHandler(CodeLocation try_location,
                                     HandlerType type) {
   // Adjust this code if not the case.
-  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
 
   // The pc (return address) is already on TOS.  This code pushes state,
-  // frame pointer and current handler.  Check that they are expected
-  // next on the stack, in that order.
-  ASSERT_EQ(StackHandlerConstants::kStateOffset,
-            StackHandlerConstants::kPCOffset - kPointerSize);
-  ASSERT_EQ(StackHandlerConstants::kFPOffset,
-            StackHandlerConstants::kStateOffset - kPointerSize);
-  ASSERT_EQ(StackHandlerConstants::kNextOffset,
-            StackHandlerConstants::kFPOffset - kPointerSize);
-
+  // frame pointer, context, and current handler.
   if (try_location == IN_JAVASCRIPT) {
     if (type == TRY_CATCH_HANDLER) {
       push(Immediate(StackHandler::TRY_CATCH));
@@ -2406,6 +2403,7 @@
       push(Immediate(StackHandler::TRY_FINALLY));
     }
     push(rbp);
+    push(rsi);
   } else {
     ASSERT(try_location == IN_JS_ENTRY);
     // The frame pointer does not point to a JS frame so we save NULL
@@ -2413,6 +2411,7 @@
     // before dereferencing it to restore the context.
     push(Immediate(StackHandler::ENTRY));
     push(Immediate(0));  // NULL frame pointer.
+    Push(Smi::FromInt(0));  // No context.
   }
   // Save the current handler.
   Operand handler_operand =
@@ -2435,12 +2434,13 @@
 
 
 void MacroAssembler::Throw(Register value) {
-  // Check that stack should contain next handler, frame pointer, state and
-  // return address in that order.
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset + kPointerSize ==
-            StackHandlerConstants::kStateOffset);
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset + kPointerSize ==
-            StackHandlerConstants::kPCOffset);
+  // Adjust this code if not the case.
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // Keep thrown value in rax.
   if (!value.is(rax)) {
     movq(rax, value);
@@ -2451,23 +2451,32 @@
   movq(rsp, handler_operand);
   // get next in chain
   pop(handler_operand);
-  pop(rbp);  // pop frame pointer
-  pop(rdx);  // remove state
+  pop(rsi);  // Context.
+  pop(rbp);  // Frame pointer.
+  pop(rdx);  // State.
 
-  // Before returning we restore the context from the frame pointer if not NULL.
-  // The frame pointer is NULL in the exception handler of a JS entry frame.
-  Set(rsi, 0);  // Tentatively set context pointer to NULL
+  // If the handler is a JS frame, restore the context to the frame.
+  // (rdx == ENTRY) == (rbp == 0) == (rsi == 0), so we could test any
+  // of them.
   Label skip;
-  cmpq(rbp, Immediate(0));
+  cmpq(rdx, Immediate(StackHandler::ENTRY));
   j(equal, &skip, Label::kNear);
-  movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
+  movq(Operand(rbp, StandardFrameConstants::kContextOffset), rsi);
   bind(&skip);
+
   ret(0);
 }
 
 
 void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
                                       Register value) {
+  // Adjust this code if not the case.
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // Keep thrown value in rax.
   if (!value.is(rax)) {
     movq(rax, value);
@@ -2507,19 +2516,13 @@
     Store(pending_exception, rax);
   }
 
-  // Clear the context pointer.
+  // Discard the context saved in the handler and clear the context pointer.
+  pop(rdx);
   Set(rsi, 0);
 
-  // Restore registers from handler.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset + kPointerSize ==
-                StackHandlerConstants::kFPOffset);
-  pop(rbp);  // FP
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset + kPointerSize ==
-                StackHandlerConstants::kStateOffset);
-  pop(rdx);  // State
+  pop(rbp);  // Restore frame pointer.
+  pop(rdx);  // Discard state.
 
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset + kPointerSize ==
-                StackHandlerConstants::kPCOffset);
   ret(0);
 }
 
@@ -2696,7 +2699,7 @@
                                              Register instance_type) {
   movq(map, FieldOperand(heap_object, HeapObject::kMapOffset));
   movzxbl(instance_type, FieldOperand(map, Map::kInstanceTypeOffset));
-  ASSERT(kNotStringTag != 0);
+  STATIC_ASSERT(kNotStringTag != 0);
   testb(instance_type, Immediate(kIsNotStringMask));
   return zero;
 }
diff --git a/src/x64/regexp-macro-assembler-x64.cc b/src/x64/regexp-macro-assembler-x64.cc
index 395466e..a782bd7 100644
--- a/src/x64/regexp-macro-assembler-x64.cc
+++ b/src/x64/regexp-macro-assembler-x64.cc
@@ -1170,12 +1170,13 @@
   }
 
   // Prepare for possible GC.
-  HandleScope handles;
+  HandleScope handles(isolate);
   Handle<Code> code_handle(re_code);
 
   Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
+
   // Current string.
-  bool is_ascii = subject->IsAsciiRepresentation();
+  bool is_ascii = subject->IsAsciiRepresentationUnderneath();
 
   ASSERT(re_code->instruction_start() <= *return_address);
   ASSERT(*return_address <=
@@ -1184,7 +1185,7 @@
   MaybeObject* result = Execution::HandleStackGuardInterrupt();
 
   if (*code_handle != re_code) {  // Return address no longer valid
-    intptr_t delta = *code_handle - re_code;
+    intptr_t delta = code_handle->address() - re_code->address();
     // Overwrite the return address on the stack.
     *return_address += delta;
   }
@@ -1193,8 +1194,20 @@
     return EXCEPTION;
   }
 
+  Handle<String> subject_tmp = subject;
+  int slice_offset = 0;
+
+  // Extract the underlying string and the slice offset.
+  if (StringShape(*subject_tmp).IsCons()) {
+    subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
+  } else if (StringShape(*subject_tmp).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(*subject_tmp);
+    subject_tmp = Handle<String>(slice->parent());
+    slice_offset = slice->offset();
+  }
+
   // String might have changed.
-  if (subject->IsAsciiRepresentation() != is_ascii) {
+  if (subject_tmp->IsAsciiRepresentation() != is_ascii) {
     // If we changed between an ASCII and an UC16 string, the specialized
     // code cannot be used, and we need to restart regexp matching from
     // scratch (including, potentially, compiling a new version of the code).
@@ -1205,8 +1218,8 @@
   // be a sequential or external string with the same content.
   // Update the start and end pointers in the stack frame to the current
   // location (whether it has actually moved or not).
-  ASSERT(StringShape(*subject).IsSequential() ||
-      StringShape(*subject).IsExternal());
+  ASSERT(StringShape(*subject_tmp).IsSequential() ||
+      StringShape(*subject_tmp).IsExternal());
 
   // The original start address of the characters to match.
   const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);
@@ -1214,7 +1227,8 @@
   // Find the current start address of the same character at the current string
   // position.
   int start_index = frame_entry<int>(re_frame, kStartIndex);
-  const byte* new_address = StringCharacterPosition(*subject, start_index);
+  const byte* new_address = StringCharacterPosition(*subject_tmp,
+                                                    start_index + slice_offset);
 
   if (start_address != new_address) {
     // If there is a difference, update the object pointer and start and end
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index b8e5f22..5ea7257 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -258,7 +258,7 @@
   // Check that the object is a string.
   __ movq(scratch, FieldOperand(receiver, HeapObject::kMapOffset));
   __ movzxbq(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
-  ASSERT(kNotStringTag != 0);
+  STATIC_ASSERT(kNotStringTag != 0);
   __ testl(scratch, Immediate(kNotStringTag));
   __ j(not_zero, non_string_object);
 }
@@ -3070,7 +3070,7 @@
   // Load the initial map and verify that it is in fact a map.
   __ movq(rbx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
   // Will both indicate a NULL and a Smi.
-  ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTag == 0);
   __ JumpIfSmi(rbx, &generic_stub_call);
   __ CmpObjectType(rbx, MAP_TYPE, rcx);
   __ j(not_equal, &generic_stub_call);
@@ -3244,7 +3244,7 @@
   // Check that the index is in range.
   __ movq(rbx, FieldOperand(rdx, JSObject::kElementsOffset));
   __ SmiToInteger32(rcx, rax);
-  __ cmpl(rcx, FieldOperand(rbx, ExternalArray::kLengthOffset));
+  __ cmpq(rax, FieldOperand(rbx, ExternalArray::kLengthOffset));
   // Unsigned comparison catches both negative and too-large values.
   __ j(above_equal, &miss_force_generic);
 
@@ -3379,7 +3379,7 @@
   // Check that the index is in range.
   __ movq(rbx, FieldOperand(rdx, JSObject::kElementsOffset));
   __ SmiToInteger32(rdi, rcx);  // Untag the index.
-  __ cmpl(rdi, FieldOperand(rbx, ExternalArray::kLengthOffset));
+  __ cmpq(rcx, FieldOperand(rbx, ExternalArray::kLengthOffset));
   // Unsigned comparison catches both negative and too-large values.
   __ j(above_equal, &miss_force_generic);
 
@@ -3752,10 +3752,11 @@
 
   __ bind(&smi_value);
   // Value is a smi. convert to a double and store.
-  __ SmiToInteger32(rax, rax);
-  __ push(rax);
+  // Preserve original value.
+  __ SmiToInteger32(rdx, rax);
+  __ push(rdx);
   __ fild_s(Operand(rsp, 0));
-  __ pop(rax);
+  __ pop(rdx);
   __ SmiToInteger32(rcx, rcx);
   __ fstp_d(FieldOperand(rdi, rcx, times_8, FixedDoubleArray::kHeaderSize));
   __ ret(0);
diff --git a/src/zone.cc b/src/zone.cc
index 42ce8c5..7574778 100644
--- a/src/zone.cc
+++ b/src/zone.cc
@@ -34,24 +34,6 @@
 namespace internal {
 
 
-Zone::Zone()
-    : zone_excess_limit_(256 * MB),
-      segment_bytes_allocated_(0),
-      position_(0),
-      limit_(0),
-      scope_nesting_(0),
-      segment_head_(NULL) {
-}
-unsigned Zone::allocation_size_ = 0;
-
-
-ZoneScope::~ZoneScope() {
-  ASSERT_EQ(Isolate::Current(), isolate_);
-  if (ShouldDeleteOnExit()) isolate_->zone()->DeleteAll();
-  isolate_->zone()->scope_nesting_--;
-}
-
-
 // Segments represent chunks of memory: They have starting address
 // (encoded in the this pointer) and a size in bytes. Segments are
 // chained together forming a LIFO structure with the newest segment
@@ -60,6 +42,11 @@
 
 class Segment {
  public:
+  void Initialize(Segment* next, int size) {
+    next_ = next;
+    size_ = size;
+  }
+
   Segment* next() const { return next_; }
   void clear_next() { next_ = NULL; }
 
@@ -77,19 +64,33 @@
 
   Segment* next_;
   int size_;
-
-  friend class Zone;
 };
 
 
+Zone::Zone()
+    : zone_excess_limit_(256 * MB),
+      segment_bytes_allocated_(0),
+      position_(0),
+      limit_(0),
+      scope_nesting_(0),
+      segment_head_(NULL) {
+}
+unsigned Zone::allocation_size_ = 0;
+
+ZoneScope::~ZoneScope() {
+  ASSERT_EQ(Isolate::Current(), isolate_);
+  if (ShouldDeleteOnExit()) isolate_->zone()->DeleteAll();
+  isolate_->zone()->scope_nesting_--;
+}
+
+
 // Creates a new segment, sets it size, and pushes it to the front
 // of the segment chain. Returns the new segment.
 Segment* Zone::NewSegment(int size) {
   Segment* result = reinterpret_cast<Segment*>(Malloced::New(size));
   adjust_segment_bytes_allocated(size);
   if (result != NULL) {
-    result->next_ = segment_head_;
-    result->size_ = size;
+    result->Initialize(segment_head_, size);
     segment_head_ = result;
   }
   return result;
@@ -155,6 +156,14 @@
 }
 
 
+void Zone::DeleteKeptSegment() {
+  if (segment_head_ != NULL) {
+    DeleteSegment(segment_head_, segment_head_->size());
+    segment_head_ = NULL;
+  }
+}
+
+
 Address Zone::NewExpand(int size) {
   // Make sure the requested size is already properly aligned and that
   // there isn't enough room in the Zone to satisfy the request.
diff --git a/src/zone.h b/src/zone.h
index abb53ad..f60ac0d 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -65,9 +65,13 @@
   template <typename T>
   inline T* NewArray(int length);
 
-  // Delete all objects and free all memory allocated in the Zone.
+  // Deletes all objects and free all memory allocated in the Zone. Keeps one
+  // small (size <= kMaximumKeptSegmentSize) segment around if it finds one.
   void DeleteAll();
 
+  // Deletes the last small segment kept around by DeleteAll().
+  void DeleteKeptSegment();
+
   // Returns true if more memory has been allocated in zones than
   // the limit allows.
   inline bool excess_allocation();
@@ -148,6 +152,7 @@
   // ZoneObjects should never be deleted individually; use
   // Zone::DeleteAll() to delete all zone objects in one go.
   void operator delete(void*, size_t) { UNREACHABLE(); }
+  void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); }
 };
 
 
@@ -193,13 +198,12 @@
       : List<T, ZoneListAllocationPolicy>(other.length()) {
     AddAll(other);
   }
+
+  void operator delete(void* pointer) { UNREACHABLE(); }
+  void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); }
 };
 
 
-// Introduce a convenience type for zone lists of map handles.
-typedef ZoneList<Handle<Map> > ZoneMapList;
-
-
 // ZoneScopes keep track of the current parsing and compilation
 // nesting and cleans up generated ASTs in the Zone when exiting the
 // outer-most scope.
diff --git a/test/benchmarks/testcfg.py b/test/benchmarks/testcfg.py
index 51d8520..ab9d40f 100644
--- a/test/benchmarks/testcfg.py
+++ b/test/benchmarks/testcfg.py
@@ -91,7 +91,7 @@
     return [test]
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     pass
diff --git a/test/cctest/SConscript b/test/cctest/SConscript
index b0a7166..621d8ec 100644
--- a/test/cctest/SConscript
+++ b/test/cctest/SConscript
@@ -65,6 +65,7 @@
     'test-debug.cc',
     'test-decls.cc',
     'test-deoptimization.cc',
+    'test-dictionary.cc',
     'test-diy-fp.cc',
     'test-double.cc',
     'test-dtoa.cc',
@@ -95,7 +96,8 @@
     'test-threads.cc',
     'test-unbound-queue.cc',
     'test-utils.cc',
-    'test-version.cc'
+    'test-version.cc',
+    'test-weakmaps.cc'
   ],
   'arch:arm':  [
     'test-assembler-arm.cc',
diff --git a/test/cctest/cctest.gyp b/test/cctest/cctest.gyp
index 9cbcb9c..c0b5316 100644
--- a/test/cctest/cctest.gyp
+++ b/test/cctest/cctest.gyp
@@ -26,10 +26,10 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 {
+  'includes': ['../../build/common.gypi'],
   'variables': {
     'generated_file': '<(SHARED_INTERMEDIATE_DIR)/resources.cc',
   },
-  'includes': [ '../../build/v8-features.gypi' ],
   'targets': [
     {
       'target_name': 'cctest',
@@ -61,6 +61,7 @@
         'test-debug.cc',
         'test-decls.cc',
         'test-deoptimization.cc',
+        'test-dictionary.cc',
         'test-diy-fp.cc',
         'test-double.cc',
         'test-dtoa.cc',
@@ -78,6 +79,7 @@
         'test-log.cc',
         'test-mark-compact.cc',
         'test-parsing.cc',
+        'test-platform-tls.cc',
         'test-profile-generator.cc',
         'test-regexp.cc',
         'test-reloc-info.cc',
diff --git a/test/cctest/cctest.status b/test/cctest/cctest.status
index 6e7824f..78f3756 100644
--- a/test/cctest/cctest.status
+++ b/test/cctest/cctest.status
@@ -38,6 +38,9 @@
 test-serialize/TestThatAlwaysFails: FAIL
 test-serialize/DependentTestThatAlwaysFails: FAIL
 
+# We do not yet shrink weak maps after they have been emptied by the GC
+test-weakmaps/Shrinking: FAIL
+
 ##############################################################################
 [ $arch == arm ]
 
diff --git a/test/cctest/test-accessors.cc b/test/cctest/test-accessors.cc
index 028f82f..d95536d 100644
--- a/test/cctest/test-accessors.cc
+++ b/test/cctest/test-accessors.cc
@@ -44,8 +44,6 @@
 using ::v8::AccessorInfo;
 using ::v8::Extension;
 
-namespace i = ::v8::internal;
-
 static v8::Handle<Value> handle_property(Local<String> name,
                                          const AccessorInfo&) {
   ApiTestFuzzer::Fuzz();
diff --git a/test/cctest/test-alloc.cc b/test/cctest/test-alloc.cc
index 4d9c218..9767192 100644
--- a/test/cctest/test-alloc.cc
+++ b/test/cctest/test-alloc.cc
@@ -186,7 +186,9 @@
 TEST(CodeRange) {
   const int code_range_size = 16*MB;
   OS::Setup();
-  Isolate::Current()->code_range()->Setup(code_range_size);
+  Isolate::Current()->InitializeLoggingAndCounters();
+  CodeRange* code_range = new CodeRange(Isolate::Current());
+  code_range->Setup(code_range_size);
   int current_allocated = 0;
   int total_allocated = 0;
   List<Block> blocks(1000);
@@ -198,8 +200,7 @@
       size_t requested = (Page::kPageSize << (Pseudorandom() % 6)) +
            Pseudorandom() % 5000 + 1;
       size_t allocated = 0;
-      void* base = Isolate::Current()->code_range()->
-          AllocateRawMemory(requested, &allocated);
+      void* base = code_range->AllocateRawMemory(requested, &allocated);
       CHECK(base != NULL);
       blocks.Add(Block(base, static_cast<int>(allocated)));
       current_allocated += static_cast<int>(allocated);
@@ -207,8 +208,7 @@
     } else {
       // Free a block.
       int index = Pseudorandom() % blocks.length();
-      Isolate::Current()->code_range()->FreeRawMemory(
-          blocks[index].base, blocks[index].size);
+      code_range->FreeRawMemory(blocks[index].base, blocks[index].size);
       current_allocated -= blocks[index].size;
       if (index < blocks.length() - 1) {
         blocks[index] = blocks.RemoveLast();
@@ -218,5 +218,6 @@
     }
   }
 
-  Isolate::Current()->code_range()->TearDown();
+  code_range->TearDown();
+  delete code_range;
 }
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 5d197be..3d40a73 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -72,8 +72,6 @@
 using ::v8::V8;
 using ::v8::Value;
 
-namespace i = ::i;
-
 
 static void ExpectString(const char* code, const char* expected) {
   Local<Value> result = CompileRun(code);
@@ -331,16 +329,14 @@
 
 class TestResource: public String::ExternalStringResource {
  public:
-  static int dispose_count;
-
-  explicit TestResource(uint16_t* data)
-      : data_(data), length_(0) {
+  explicit TestResource(uint16_t* data, int* counter = NULL)
+    : data_(data), length_(0), counter_(counter) {
     while (data[length_]) ++length_;
   }
 
   ~TestResource() {
     i::DeleteArray(data_);
-    ++dispose_count;
+    if (counter_ != NULL) ++*counter_;
   }
 
   const uint16_t* data() const {
@@ -353,23 +349,18 @@
  private:
   uint16_t* data_;
   size_t length_;
+  int* counter_;
 };
 
 
-int TestResource::dispose_count = 0;
-
-
 class TestAsciiResource: public String::ExternalAsciiStringResource {
  public:
-  static int dispose_count;
-
-  explicit TestAsciiResource(const char* data)
-      : data_(data),
-        length_(strlen(data)) { }
+  explicit TestAsciiResource(const char* data, int* counter = NULL)
+    : data_(data), length_(strlen(data)), counter_(counter) { }
 
   ~TestAsciiResource() {
     i::DeleteArray(data_);
-    ++dispose_count;
+    if (counter_ != NULL) ++*counter_;
   }
 
   const char* data() const {
@@ -382,20 +373,18 @@
  private:
   const char* data_;
   size_t length_;
+  int* counter_;
 };
 
 
-int TestAsciiResource::dispose_count = 0;
-
-
 THREADED_TEST(ScriptUsingStringResource) {
-  TestResource::dispose_count = 0;
+  int dispose_count = 0;
   const char* c_source = "1 + 2 * 3";
   uint16_t* two_byte_source = AsciiToTwoByteString(c_source);
   {
     v8::HandleScope scope;
     LocalContext env;
-    TestResource* resource = new TestResource(two_byte_source);
+    TestResource* resource = new TestResource(two_byte_source, &dispose_count);
     Local<String> source = String::NewExternal(resource);
     Local<Script> script = Script::Compile(source);
     Local<Value> value = script->Run();
@@ -405,37 +394,38 @@
     CHECK_EQ(resource,
              static_cast<TestResource*>(source->GetExternalStringResource()));
     HEAP->CollectAllGarbage(false);
-    CHECK_EQ(0, TestResource::dispose_count);
+    CHECK_EQ(0, dispose_count);
   }
   v8::internal::Isolate::Current()->compilation_cache()->Clear();
   HEAP->CollectAllGarbage(false);
-  CHECK_EQ(1, TestResource::dispose_count);
+  CHECK_EQ(1, dispose_count);
 }
 
 
 THREADED_TEST(ScriptUsingAsciiStringResource) {
-  TestAsciiResource::dispose_count = 0;
+  int dispose_count = 0;
   const char* c_source = "1 + 2 * 3";
   {
     v8::HandleScope scope;
     LocalContext env;
     Local<String> source =
-        String::NewExternal(new TestAsciiResource(i::StrDup(c_source)));
+        String::NewExternal(new TestAsciiResource(i::StrDup(c_source),
+                                                  &dispose_count));
     Local<Script> script = Script::Compile(source);
     Local<Value> value = script->Run();
     CHECK(value->IsNumber());
     CHECK_EQ(7, value->Int32Value());
     HEAP->CollectAllGarbage(false);
-    CHECK_EQ(0, TestAsciiResource::dispose_count);
+    CHECK_EQ(0, dispose_count);
   }
   i::Isolate::Current()->compilation_cache()->Clear();
   HEAP->CollectAllGarbage(false);
-  CHECK_EQ(1, TestAsciiResource::dispose_count);
+  CHECK_EQ(1, dispose_count);
 }
 
 
 THREADED_TEST(ScriptMakingExternalString) {
-  TestResource::dispose_count = 0;
+  int dispose_count = 0;
   uint16_t* two_byte_source = AsciiToTwoByteString("1 + 2 * 3");
   {
     v8::HandleScope scope;
@@ -444,23 +434,24 @@
     // Trigger GCs so that the newly allocated string moves to old gen.
     HEAP->CollectGarbage(i::NEW_SPACE);  // in survivor space now
     HEAP->CollectGarbage(i::NEW_SPACE);  // in old gen now
-    bool success = source->MakeExternal(new TestResource(two_byte_source));
+    bool success = source->MakeExternal(new TestResource(two_byte_source,
+                                                         &dispose_count));
     CHECK(success);
     Local<Script> script = Script::Compile(source);
     Local<Value> value = script->Run();
     CHECK(value->IsNumber());
     CHECK_EQ(7, value->Int32Value());
     HEAP->CollectAllGarbage(false);
-    CHECK_EQ(0, TestResource::dispose_count);
+    CHECK_EQ(0, dispose_count);
   }
   i::Isolate::Current()->compilation_cache()->Clear();
   HEAP->CollectAllGarbage(false);
-  CHECK_EQ(1, TestResource::dispose_count);
+  CHECK_EQ(1, dispose_count);
 }
 
 
 THREADED_TEST(ScriptMakingExternalAsciiString) {
-  TestAsciiResource::dispose_count = 0;
+  int dispose_count = 0;
   const char* c_source = "1 + 2 * 3";
   {
     v8::HandleScope scope;
@@ -470,18 +461,18 @@
     HEAP->CollectGarbage(i::NEW_SPACE);  // in survivor space now
     HEAP->CollectGarbage(i::NEW_SPACE);  // in old gen now
     bool success = source->MakeExternal(
-        new TestAsciiResource(i::StrDup(c_source)));
+        new TestAsciiResource(i::StrDup(c_source), &dispose_count));
     CHECK(success);
     Local<Script> script = Script::Compile(source);
     Local<Value> value = script->Run();
     CHECK(value->IsNumber());
     CHECK_EQ(7, value->Int32Value());
     HEAP->CollectAllGarbage(false);
-    CHECK_EQ(0, TestAsciiResource::dispose_count);
+    CHECK_EQ(0, dispose_count);
   }
   i::Isolate::Current()->compilation_cache()->Clear();
   HEAP->CollectAllGarbage(false);
-  CHECK_EQ(1, TestAsciiResource::dispose_count);
+  CHECK_EQ(1, dispose_count);
 }
 
 
@@ -605,49 +596,52 @@
 
 
 THREADED_TEST(ScavengeExternalString) {
-  TestResource::dispose_count = 0;
+  int dispose_count = 0;
   bool in_new_space = false;
   {
     v8::HandleScope scope;
     uint16_t* two_byte_string = AsciiToTwoByteString("test string");
     Local<String> string =
-        String::NewExternal(new TestResource(two_byte_string));
+      String::NewExternal(new TestResource(two_byte_string,
+                                           &dispose_count));
     i::Handle<i::String> istring = v8::Utils::OpenHandle(*string);
     HEAP->CollectGarbage(i::NEW_SPACE);
     in_new_space = HEAP->InNewSpace(*istring);
     CHECK(in_new_space || HEAP->old_data_space()->Contains(*istring));
-    CHECK_EQ(0, TestResource::dispose_count);
+    CHECK_EQ(0, dispose_count);
   }
   HEAP->CollectGarbage(in_new_space ? i::NEW_SPACE : i::OLD_DATA_SPACE);
-  CHECK_EQ(1, TestResource::dispose_count);
+  CHECK_EQ(1, dispose_count);
 }
 
 
 THREADED_TEST(ScavengeExternalAsciiString) {
-  TestAsciiResource::dispose_count = 0;
+  int dispose_count = 0;
   bool in_new_space = false;
   {
     v8::HandleScope scope;
     const char* one_byte_string = "test string";
     Local<String> string = String::NewExternal(
-        new TestAsciiResource(i::StrDup(one_byte_string)));
+        new TestAsciiResource(i::StrDup(one_byte_string), &dispose_count));
     i::Handle<i::String> istring = v8::Utils::OpenHandle(*string);
     HEAP->CollectGarbage(i::NEW_SPACE);
     in_new_space = HEAP->InNewSpace(*istring);
     CHECK(in_new_space || HEAP->old_data_space()->Contains(*istring));
-    CHECK_EQ(0, TestAsciiResource::dispose_count);
+    CHECK_EQ(0, dispose_count);
   }
   HEAP->CollectGarbage(in_new_space ? i::NEW_SPACE : i::OLD_DATA_SPACE);
-  CHECK_EQ(1, TestAsciiResource::dispose_count);
+  CHECK_EQ(1, dispose_count);
 }
 
 
 class TestAsciiResourceWithDisposeControl: public TestAsciiResource {
  public:
+  // Only used by non-threaded tests, so it can use static fields.
   static int dispose_calls;
+  static int dispose_count;
 
   TestAsciiResourceWithDisposeControl(const char* data, bool dispose)
-      : TestAsciiResource(data),
+      : TestAsciiResource(data, &dispose_count),
         dispose_(dispose) { }
 
   void Dispose() {
@@ -659,6 +653,7 @@
 };
 
 
+int TestAsciiResourceWithDisposeControl::dispose_count = 0;
 int TestAsciiResourceWithDisposeControl::dispose_calls = 0;
 
 
@@ -666,7 +661,7 @@
   const char* c_source = "1 + 2 * 3";
 
   // Use a stack allocated external string resource allocated object.
-  TestAsciiResource::dispose_count = 0;
+  TestAsciiResourceWithDisposeControl::dispose_count = 0;
   TestAsciiResourceWithDisposeControl::dispose_calls = 0;
   TestAsciiResourceWithDisposeControl res_stack(i::StrDup(c_source), false);
   {
@@ -678,15 +673,15 @@
     CHECK(value->IsNumber());
     CHECK_EQ(7, value->Int32Value());
     HEAP->CollectAllGarbage(false);
-    CHECK_EQ(0, TestAsciiResource::dispose_count);
+    CHECK_EQ(0, TestAsciiResourceWithDisposeControl::dispose_count);
   }
   i::Isolate::Current()->compilation_cache()->Clear();
   HEAP->CollectAllGarbage(false);
   CHECK_EQ(1, TestAsciiResourceWithDisposeControl::dispose_calls);
-  CHECK_EQ(0, TestAsciiResource::dispose_count);
+  CHECK_EQ(0, TestAsciiResourceWithDisposeControl::dispose_count);
 
   // Use a heap allocated external string resource allocated object.
-  TestAsciiResource::dispose_count = 0;
+  TestAsciiResourceWithDisposeControl::dispose_count = 0;
   TestAsciiResourceWithDisposeControl::dispose_calls = 0;
   TestAsciiResource* res_heap =
       new TestAsciiResourceWithDisposeControl(i::StrDup(c_source), true);
@@ -699,12 +694,12 @@
     CHECK(value->IsNumber());
     CHECK_EQ(7, value->Int32Value());
     HEAP->CollectAllGarbage(false);
-    CHECK_EQ(0, TestAsciiResource::dispose_count);
+    CHECK_EQ(0, TestAsciiResourceWithDisposeControl::dispose_count);
   }
   i::Isolate::Current()->compilation_cache()->Clear();
   HEAP->CollectAllGarbage(false);
   CHECK_EQ(1, TestAsciiResourceWithDisposeControl::dispose_calls);
-  CHECK_EQ(1, TestAsciiResource::dispose_count);
+  CHECK_EQ(1, TestAsciiResourceWithDisposeControl::dispose_count);
 }
 
 
@@ -828,7 +823,7 @@
 static v8::Handle<v8::Value> callback(const v8::Arguments& args) {
   void* ptr = v8::External::Unwrap(args.Data());
   CHECK_EQ(expected_ptr, ptr);
-  return v8::Boolean::New(true);
+  return v8::True();
 }
 
 
@@ -2642,7 +2637,7 @@
 
 
 v8::Handle<Value> CCatcher(const v8::Arguments& args) {
-  if (args.Length() < 1) return v8::Boolean::New(false);
+  if (args.Length() < 1) return v8::False();
   v8::HandleScope scope;
   v8::TryCatch try_catch;
   Local<Value> result = v8::Script::Compile(args[0]->ToString())->Run();
@@ -3588,6 +3583,114 @@
 }
 
 
+static v8::Handle<Value> UnboxedDoubleIndexedPropertyGetter(
+    uint32_t index,
+    const AccessorInfo& info) {
+  ApiTestFuzzer::Fuzz();
+  if (index < 25) {
+    return v8::Handle<Value>(v8_num(index));
+  }
+  return v8::Handle<Value>();
+}
+
+
+static v8::Handle<Value> UnboxedDoubleIndexedPropertySetter(
+    uint32_t index,
+    Local<Value> value,
+    const AccessorInfo& info) {
+  ApiTestFuzzer::Fuzz();
+  if (index < 25) {
+    return v8::Handle<Value>(v8_num(index));
+  }
+  return v8::Handle<Value>();
+}
+
+
+Handle<v8::Array> UnboxedDoubleIndexedPropertyEnumerator(
+    const AccessorInfo& info) {
+  // Force the list of returned keys to be stored in a FastDoubleArray.
+  Local<Script> indexed_property_names_script = Script::Compile(v8_str(
+      "keys = new Array(); keys[125000] = 1;"
+      "for(i = 0; i < 80000; i++) { keys[i] = i; };"
+      "keys.length = 25; keys;"));
+  Local<Value> result = indexed_property_names_script->Run();
+  return Local<v8::Array>(::v8::Array::Cast(*result));
+}
+
+
+// Make sure that the the interceptor code in the runtime properly handles
+// merging property name lists for double-array-backed arrays.
+THREADED_TEST(IndexedInterceptorUnboxedDoubleWithIndexedAccessor) {
+  v8::HandleScope scope;
+  Local<ObjectTemplate> templ = ObjectTemplate::New();
+  templ->SetIndexedPropertyHandler(UnboxedDoubleIndexedPropertyGetter,
+                                   UnboxedDoubleIndexedPropertySetter,
+                                   0,
+                                   0,
+                                   UnboxedDoubleIndexedPropertyEnumerator);
+  LocalContext context;
+  context->Global()->Set(v8_str("obj"), templ->NewInstance());
+  // When obj is created, force it to be Stored in a FastDoubleArray.
+  Local<Script> create_unboxed_double_script = Script::Compile(v8_str(
+      "obj[125000] = 1; for(i = 0; i < 80000; i+=2) { obj[i] = i; } "
+      "key_count = 0; "
+      "for (x in obj) {key_count++;};"
+      "obj;"));
+  Local<Value> result = create_unboxed_double_script->Run();
+  CHECK(result->ToObject()->HasRealIndexedProperty(2000));
+  Local<Script> key_count_check = Script::Compile(v8_str(
+      "key_count;"));
+  result = key_count_check->Run();
+  CHECK_EQ(v8_num(40013), result);
+}
+
+
+Handle<v8::Array> NonStrictArgsIndexedPropertyEnumerator(
+    const AccessorInfo& info) {
+  // Force the list of returned keys to be stored in a Arguments object.
+  Local<Script> indexed_property_names_script = Script::Compile(v8_str(
+      "function f(w,x) {"
+      " return arguments;"
+      "}"
+      "keys = f(0, 1, 2, 3);"
+      "keys;"));
+  Local<Value> result = indexed_property_names_script->Run();
+  return Local<v8::Array>(static_cast<v8::Array*>(::v8::Object::Cast(*result)));
+}
+
+
+static v8::Handle<Value> NonStrictIndexedPropertyGetter(
+    uint32_t index,
+    const AccessorInfo& info) {
+  ApiTestFuzzer::Fuzz();
+  if (index < 4) {
+    return v8::Handle<Value>(v8_num(index));
+  }
+  return v8::Handle<Value>();
+}
+
+
+// Make sure that the the interceptor code in the runtime properly handles
+// merging property name lists for non-string arguments arrays.
+THREADED_TEST(IndexedInterceptorNonStrictArgsWithIndexedAccessor) {
+  v8::HandleScope scope;
+  Local<ObjectTemplate> templ = ObjectTemplate::New();
+  templ->SetIndexedPropertyHandler(NonStrictIndexedPropertyGetter,
+                                   0,
+                                   0,
+                                   0,
+                                   NonStrictArgsIndexedPropertyEnumerator);
+  LocalContext context;
+  context->Global()->Set(v8_str("obj"), templ->NewInstance());
+  Local<Script> create_args_script =
+      Script::Compile(v8_str(
+          "var key_count = 0;"
+          "for (x in obj) {key_count++;} key_count;"));
+  Local<Value> result = create_args_script->Run();
+  CHECK_EQ(v8_num(4), result);
+}
+
+
 static v8::Handle<Value> IdentityIndexedPropertyGetter(
     uint32_t index,
     const AccessorInfo& info) {
@@ -5221,6 +5324,40 @@
   CHECK_EQ(0, strncmp("d\1", buf, 2));
   uint16_t answer7[] = {'d', 0x101};
   CHECK_EQ(0, StrNCmp16(answer7, wbuf, 2));
+
+  memset(wbuf, 0x1, sizeof(wbuf));
+  wbuf[5] = 'X';
+  len = str->Write(wbuf, 0, 6, String::NO_NULL_TERMINATION);
+  CHECK_EQ(5, len);
+  CHECK_EQ('X', wbuf[5]);
+  uint16_t answer8a[] = {'a', 'b', 'c', 'd', 'e'};
+  uint16_t answer8b[] = {'a', 'b', 'c', 'd', 'e', '\0'};
+  CHECK_EQ(0, StrNCmp16(answer8a, wbuf, 5));
+  CHECK_NE(0, StrCmp16(answer8b, wbuf));
+  wbuf[5] = '\0';
+  CHECK_EQ(0, StrCmp16(answer8b, wbuf));
+
+  memset(buf, 0x1, sizeof(buf));
+  buf[5] = 'X';
+  len = str->WriteAscii(buf, 0, 6, String::NO_NULL_TERMINATION);
+  CHECK_EQ(5, len);
+  CHECK_EQ('X', buf[5]);
+  CHECK_EQ(0, strncmp("abcde", buf, 5));
+  CHECK_NE(0, strcmp("abcde", buf));
+  buf[5] = '\0';
+  CHECK_EQ(0, strcmp("abcde", buf));
+
+  memset(utf8buf, 0x1, sizeof(utf8buf));
+  utf8buf[8] = 'X';
+  len = str2->WriteUtf8(utf8buf, sizeof(utf8buf), &charlen,
+                        String::NO_NULL_TERMINATION);
+  CHECK_EQ(8, len);
+  CHECK_EQ('X', utf8buf[8]);
+  CHECK_EQ(5, charlen);
+  CHECK_EQ(0, strncmp(utf8buf, "abc\303\260\342\230\203", 8));
+  CHECK_NE(0, strcmp(utf8buf, "abc\303\260\342\230\203"));
+  utf8buf[8] = '\0';
+  CHECK_EQ(0, strcmp(utf8buf, "abc\303\260\342\230\203"));
 }
 
 
@@ -7021,53 +7158,34 @@
 }
 
 
-THREADED_TEST(SetPrototypeProperties) {
+THREADED_TEST(FunctionReadOnlyPrototype) {
   v8::HandleScope handle_scope;
   LocalContext context;
 
   Local<v8::FunctionTemplate> t1 = v8::FunctionTemplate::New();
-  t1->SetPrototypeAttributes(v8::DontDelete);
+  t1->PrototypeTemplate()->Set(v8_str("x"), v8::Integer::New(42));
+  t1->ReadOnlyPrototype();
   context->Global()->Set(v8_str("func1"), t1->GetFunction());
+  // Configured value of ReadOnly flag.
   CHECK(CompileRun(
       "(function() {"
       "  descriptor = Object.getOwnPropertyDescriptor(func1, 'prototype');"
-      "  return (descriptor['writable'] == true) &&"
-      "         (descriptor['enumerable'] == true) &&"
-      "         (descriptor['configurable'] == false);"
+      "  return (descriptor['writable'] == false);"
       "})()")->BooleanValue());
+  CHECK_EQ(42, CompileRun("func1.prototype.x")->Int32Value());
+  CHECK_EQ(42,
+           CompileRun("func1.prototype = {}; func1.prototype.x")->Int32Value());
 
   Local<v8::FunctionTemplate> t2 = v8::FunctionTemplate::New();
-  t2->SetPrototypeAttributes(v8::DontEnum);
+  t2->PrototypeTemplate()->Set(v8_str("x"), v8::Integer::New(42));
   context->Global()->Set(v8_str("func2"), t2->GetFunction());
+  // Default value of ReadOnly flag.
   CHECK(CompileRun(
       "(function() {"
       "  descriptor = Object.getOwnPropertyDescriptor(func2, 'prototype');"
-      "  return (descriptor['writable'] == true) &&"
-      "         (descriptor['enumerable'] == false) &&"
-      "         (descriptor['configurable'] == true);"
+      "  return (descriptor['writable'] == true);"
       "})()")->BooleanValue());
-
-  Local<v8::FunctionTemplate> t3 = v8::FunctionTemplate::New();
-  t3->SetPrototypeAttributes(v8::ReadOnly);
-  context->Global()->Set(v8_str("func3"), t3->GetFunction());
-  CHECK(CompileRun(
-      "(function() {"
-      "  descriptor = Object.getOwnPropertyDescriptor(func3, 'prototype');"
-      "  return (descriptor['writable'] == false) &&"
-      "         (descriptor['enumerable'] == true) &&"
-      "         (descriptor['configurable'] == true);"
-      "})()")->BooleanValue());
-
-  Local<v8::FunctionTemplate> t4 = v8::FunctionTemplate::New();
-  t4->SetPrototypeAttributes(v8::ReadOnly | v8::DontEnum | v8::DontDelete);
-  context->Global()->Set(v8_str("func4"), t4->GetFunction());
-  CHECK(CompileRun(
-      "(function() {"
-      "  descriptor = Object.getOwnPropertyDescriptor(func4, 'prototype');"
-      "  return (descriptor['writable'] == false) &&"
-      "         (descriptor['enumerable'] == false) &&"
-      "         (descriptor['configurable'] == false);"
-      "})()")->BooleanValue());
+  CHECK_EQ(42, CompileRun("func2.prototype.x")->Int32Value());
 }
 
 
@@ -7206,7 +7324,7 @@
     CHECK(value->IsBoolean());
     CHECK_EQ(true, value->BooleanValue());
 
-    Handle<Value> args3[] = { v8::Boolean::New(true) };
+    Handle<Value> args3[] = { v8::True() };
     Local<Value> value_obj3 = instance->CallAsConstructor(1, args3);
     CHECK(value_obj3->IsObject());
     Local<Object> object3 = Local<Object>::Cast(value_obj3);
@@ -9477,10 +9595,7 @@
 
 static v8::Handle<Value> IsConstructHandler(const v8::Arguments& args) {
   ApiTestFuzzer::Fuzz();
-  if (args.IsConstructCall()) {
-    return v8::Boolean::New(true);
-  }
-  return v8::Boolean::New(false);
+  return v8::Boolean::New(args.IsConstructCall());
 }
 
 
@@ -11646,7 +11761,7 @@
   }
   HEAP->CollectAllGarbage(false);  // Force GC to trigger verification.
   for (int i = 0; i < kElementCount; i++) {
-    CHECK_EQ(i % 256, pixels->get(i));
+    CHECK_EQ(i % 256, pixels->get_scalar(i));
     CHECK_EQ(i % 256, pixel_data[i]);
   }
 
@@ -12119,7 +12234,8 @@
   }
   HEAP->CollectAllGarbage(false);  // Force GC to trigger verification.
   for (int i = 0; i < kElementCount; i++) {
-    CHECK_EQ(static_cast<int64_t>(i), static_cast<int64_t>(array->get(i)));
+    CHECK_EQ(static_cast<int64_t>(i),
+             static_cast<int64_t>(array->get_scalar(i)));
     CHECK_EQ(static_cast<int64_t>(i), static_cast<int64_t>(array_data[i]));
   }
 
@@ -13636,6 +13752,9 @@
       "str2;";
   Local<Value> result = CompileRun(init_code);
 
+  Local<Value> indexof = CompileRun("str2.indexOf('els')");
+  Local<Value> lastindexof = CompileRun("str2.lastIndexOf('dab')");
+
   CHECK(result->IsString());
   i::Handle<i::String> string = v8::Utils::OpenHandle(String::Cast(*result));
   int length = string->length();
@@ -13701,6 +13820,10 @@
 
   ExpectString("str2.charAt(2);", "e");
 
+  ExpectObject("str2.indexOf('els');", indexof);
+
+  ExpectObject("str2.lastIndexOf('dab');", lastindexof);
+
   reresult = CompileRun("str2.charCodeAt(2);");
   CHECK_EQ(static_cast<int32_t>('e'), reresult->Int32Value());
 }
@@ -14354,34 +14477,34 @@
   v8::Handle<v8::RegExp> re = v8::RegExp::New(v8_str("foo"), v8::RegExp::kNone);
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("foo")));
-  CHECK_EQ(re->GetFlags(), v8::RegExp::kNone);
+  CHECK_EQ(v8::RegExp::kNone, re->GetFlags());
 
   re = v8::RegExp::New(v8_str("bar"),
                        static_cast<v8::RegExp::Flags>(v8::RegExp::kIgnoreCase |
                                                       v8::RegExp::kGlobal));
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("bar")));
-  CHECK_EQ(static_cast<int>(re->GetFlags()),
-           v8::RegExp::kIgnoreCase | v8::RegExp::kGlobal);
+  CHECK_EQ(v8::RegExp::kIgnoreCase | v8::RegExp::kGlobal,
+           static_cast<int>(re->GetFlags()));
 
   re = v8::RegExp::New(v8_str("baz"),
                        static_cast<v8::RegExp::Flags>(v8::RegExp::kIgnoreCase |
                                                       v8::RegExp::kMultiline));
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("baz")));
-  CHECK_EQ(static_cast<int>(re->GetFlags()),
-           v8::RegExp::kIgnoreCase | v8::RegExp::kMultiline);
+  CHECK_EQ(v8::RegExp::kIgnoreCase | v8::RegExp::kMultiline,
+           static_cast<int>(re->GetFlags()));
 
   re = CompileRun("/quux/").As<v8::RegExp>();
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("quux")));
-  CHECK_EQ(re->GetFlags(), v8::RegExp::kNone);
+  CHECK_EQ(v8::RegExp::kNone, re->GetFlags());
 
   re = CompileRun("/quux/gm").As<v8::RegExp>();
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("quux")));
-  CHECK_EQ(static_cast<int>(re->GetFlags()),
-           v8::RegExp::kGlobal | v8::RegExp::kMultiline);
+  CHECK_EQ(v8::RegExp::kGlobal | v8::RegExp::kMultiline,
+           static_cast<int>(re->GetFlags()));
 
   // Override the RegExp constructor and check the API constructor
   // still works.
@@ -14390,15 +14513,15 @@
   re = v8::RegExp::New(v8_str("foobar"), v8::RegExp::kNone);
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("foobar")));
-  CHECK_EQ(re->GetFlags(), v8::RegExp::kNone);
+  CHECK_EQ(v8::RegExp::kNone, re->GetFlags());
 
   re = v8::RegExp::New(v8_str("foobarbaz"),
                        static_cast<v8::RegExp::Flags>(v8::RegExp::kIgnoreCase |
                                                       v8::RegExp::kMultiline));
   CHECK(re->IsRegExp());
   CHECK(re->GetSource()->Equals(v8_str("foobarbaz")));
-  CHECK_EQ(static_cast<int>(re->GetFlags()),
-           v8::RegExp::kIgnoreCase | v8::RegExp::kMultiline);
+  CHECK_EQ(v8::RegExp::kIgnoreCase | v8::RegExp::kMultiline,
+           static_cast<int>(re->GetFlags()));
 
   context->Global()->Set(v8_str("re"), re);
   ExpectTrue("re.test('FoobarbaZ')");
@@ -14579,6 +14702,24 @@
 }
 
 
+THREADED_TEST(CreationContextOfJsFunction) {
+  HandleScope handle_scope;
+  Persistent<Context> context = Context::New();
+  InstallContextId(context, 1);
+
+  Local<Object> function;
+  {
+    Context::Scope scope(context);
+    function = CompileRun("function foo() {}; foo").As<Object>();
+  }
+
+  CHECK(function->CreationContext() == context);
+  CheckContextId(function, 1);
+
+  context.Dispose();
+}
+
+
 Handle<Value> HasOwnPropertyIndexedPropertyGetter(uint32_t index,
                                                   const AccessorInfo& info) {
   if (index == 42) return v8_str("yes");
@@ -14930,3 +15071,107 @@
 
   context.Dispose();
 }
+
+
+static void TestReceiver(Local<Value> expected_result,
+                         Local<Value> expected_receiver,
+                         const char* code) {
+  Local<Value> result = CompileRun(code);
+  CHECK(result->IsObject());
+  CHECK(expected_receiver->Equals(result->ToObject()->Get(1)));
+  CHECK(expected_result->Equals(result->ToObject()->Get(0)));
+}
+
+
+THREADED_TEST(ForeignFunctionReceiver) {
+  HandleScope scope;
+
+  // Create two contexts with different "id" properties ('i' and 'o').
+  // Call a function both from its own context and from a the foreign
+  // context, and see what "this" is bound to (returning both "this"
+  // and "this.id" for comparison).
+
+  Persistent<Context> foreign_context = v8::Context::New();
+  foreign_context->Enter();
+  Local<Value> foreign_function =
+    CompileRun("function func() { return { 0: this.id, "
+               "                           1: this, "
+               "                           toString: function() { "
+               "                               return this[0];"
+               "                           }"
+               "                         };"
+               "}"
+               "var id = 'i';"
+               "func;");
+  CHECK(foreign_function->IsFunction());
+  foreign_context->Exit();
+
+  LocalContext context;
+
+  Local<String> password = v8_str("Password");
+  // Don't get hit by security checks when accessing foreign_context's
+  // global receiver (aka. global proxy).
+  context->SetSecurityToken(password);
+  foreign_context->SetSecurityToken(password);
+
+  Local<String> i = v8_str("i");
+  Local<String> o = v8_str("o");
+  Local<String> id = v8_str("id");
+
+  CompileRun("function ownfunc() { return { 0: this.id, "
+             "                              1: this, "
+             "                              toString: function() { "
+             "                                  return this[0];"
+             "                              }"
+             "                             };"
+             "}"
+             "var id = 'o';"
+             "ownfunc");
+  context->Global()->Set(v8_str("func"), foreign_function);
+
+  // Sanity check the contexts.
+  CHECK(i->Equals(foreign_context->Global()->Get(id)));
+  CHECK(o->Equals(context->Global()->Get(id)));
+
+  // Checking local function's receiver.
+  // Calling function using its call/apply methods.
+  TestReceiver(o, context->Global(), "ownfunc.call()");
+  TestReceiver(o, context->Global(), "ownfunc.apply()");
+  // Making calls through built-in functions.
+  TestReceiver(o, context->Global(), "[1].map(ownfunc)[0]");
+  CHECK(o->Equals(CompileRun("'abcbd'.replace(/b/,ownfunc)[1]")));
+  CHECK(o->Equals(CompileRun("'abcbd'.replace(/b/g,ownfunc)[1]")));
+  CHECK(o->Equals(CompileRun("'abcbd'.replace(/b/g,ownfunc)[3]")));
+  // Calling with environment record as base.
+  TestReceiver(o, context->Global(), "ownfunc()");
+  // Calling with no base.
+  TestReceiver(o, context->Global(), "(1,ownfunc)()");
+
+  // Checking foreign function return value.
+  // Calling function using its call/apply methods.
+  TestReceiver(i, foreign_context->Global(), "func.call()");
+  TestReceiver(i, foreign_context->Global(), "func.apply()");
+  // Calling function using another context's call/apply methods.
+  TestReceiver(i, foreign_context->Global(),
+               "Function.prototype.call.call(func)");
+  TestReceiver(i, foreign_context->Global(),
+               "Function.prototype.call.apply(func)");
+  TestReceiver(i, foreign_context->Global(),
+               "Function.prototype.apply.call(func)");
+  TestReceiver(i, foreign_context->Global(),
+               "Function.prototype.apply.apply(func)");
+  // Making calls through built-in functions.
+  TestReceiver(i, foreign_context->Global(), "[1].map(func)[0]");
+  // ToString(func()) is func()[0], i.e., the returned this.id.
+  CHECK(i->Equals(CompileRun("'abcbd'.replace(/b/,func)[1]")));
+  CHECK(i->Equals(CompileRun("'abcbd'.replace(/b/g,func)[1]")));
+  CHECK(i->Equals(CompileRun("'abcbd'.replace(/b/g,func)[3]")));
+
+  // TODO(1547): Make the following also return "i".
+  // Calling with environment record as base.
+  TestReceiver(o, context->Global(), "func()");
+  // Calling with no base.
+  TestReceiver(o, context->Global(), "(1,func)()");
+
+  foreign_context.Dispose();
+}
diff --git a/test/cctest/test-assembler-arm.cc b/test/cctest/test-assembler-arm.cc
index 1703203..ecbf956 100644
--- a/test/cctest/test-assembler-arm.cc
+++ b/test/cctest/test-assembler-arm.cc
@@ -1010,4 +1010,18 @@
   CHECK_EQ(0xffffffff, i.d);
 }
 
+
+TEST(12) {
+  // Test chaining of label usages within instructions (issue 1644).
+  InitializeVM();
+  v8::HandleScope scope;
+  Assembler assm(Isolate::Current(), NULL, 0);
+
+  Label target;
+  __ b(eq, &target);
+  __ b(ne, &target);
+  __ bind(&target);
+  __ nop();
+}
+
 #undef __
diff --git a/test/cctest/test-assembler-ia32.cc b/test/cctest/test-assembler-ia32.cc
index e9d799b..839b7f5 100644
--- a/test/cctest/test-assembler-ia32.cc
+++ b/test/cctest/test-assembler-ia32.cc
@@ -394,4 +394,18 @@
   CHECK_EQ(kNaN, f(OS::nan_value(), 1.1));
 }
 
+
+TEST(AssemblerIa3210) {
+  // Test chaining of label usages within instructions (issue 1644).
+  InitializeVM();
+  v8::HandleScope scope;
+  Assembler assm(Isolate::Current(), NULL, 0);
+
+  Label target;
+  __ j(equal, &target);
+  __ j(not_equal, &target);
+  __ bind(&target);
+  __ nop();
+}
+
 #undef __
diff --git a/test/cctest/test-assembler-mips.cc b/test/cctest/test-assembler-mips.cc
index 8ac89f6..ca11a2a 100644
--- a/test/cctest/test-assembler-mips.cc
+++ b/test/cctest/test-assembler-mips.cc
@@ -1083,17 +1083,17 @@
     CpuFeatures::Scope scope(FPU);
 
     __ sw(t0, MemOperand(a0, OFFSET_OF(T, cvt_small_in)));
-    __ Cvt_d_uw(f10, t0);
+    __ Cvt_d_uw(f10, t0, f22);
     __ sdc1(f10, MemOperand(a0, OFFSET_OF(T, cvt_small_out)));
 
-    __ Trunc_uw_d(f10, f10);
+    __ Trunc_uw_d(f10, f10, f22);
     __ swc1(f10, MemOperand(a0, OFFSET_OF(T, trunc_small_out)));
 
     __ sw(t0, MemOperand(a0, OFFSET_OF(T, cvt_big_in)));
-    __ Cvt_d_uw(f8, t0);
+    __ Cvt_d_uw(f8, t0, f22);
     __ sdc1(f8, MemOperand(a0, OFFSET_OF(T, cvt_big_out)));
 
-    __ Trunc_uw_d(f8, f8);
+    __ Trunc_uw_d(f8, f8, f22);
     __ swc1(f8, MemOperand(a0, OFFSET_OF(T, trunc_big_out)));
 
     __ jr(ra);
@@ -1259,4 +1259,18 @@
   }
 }
 
+
+TEST(MIPS15) {
+  // Test chaining of label usages within instructions (issue 1644).
+  InitializeVM();
+  v8::HandleScope scope;
+  Assembler assm(Isolate::Current(), NULL, 0);
+
+  Label target;
+  __ beq(v0, v1, &target);
+  __ bne(v0, v1, &target);
+  __ bind(&target);
+  __ nop();
+}
+
 #undef __
diff --git a/test/cctest/test-assembler-x64.cc b/test/cctest/test-assembler-x64.cc
index ea70f54..28f7c9b 100644
--- a/test/cctest/test-assembler-x64.cc
+++ b/test/cctest/test-assembler-x64.cc
@@ -46,6 +46,7 @@
 using v8::internal::byte;
 using v8::internal::greater;
 using v8::internal::less_equal;
+using v8::internal::equal;
 using v8::internal::not_equal;
 using v8::internal::r13;
 using v8::internal::r15;
@@ -345,4 +346,17 @@
   }
 }
 
+
+TEST(AssemblerX64LabelChaining) {
+  // Test chaining of label usages within instructions (issue 1644).
+  v8::HandleScope scope;
+  Assembler assm(Isolate::Current(), NULL, 0);
+
+  Label target;
+  __ j(equal, &target);
+  __ j(not_equal, &target);
+  __ bind(&target);
+  __ nop();
+}
+
 #undef __
diff --git a/test/cctest/test-ast.cc b/test/cctest/test-ast.cc
index 786a54a..2aa7207 100644
--- a/test/cctest/test-ast.cc
+++ b/test/cctest/test-ast.cc
@@ -56,14 +56,3 @@
   CHECK_EQ(0, list->length());
   delete list;
 }
-
-
-TEST(DeleteEmpty) {
-  {
-    List<int>* list = new List<int>(0);
-    delete list;
-  }
-  {
-    List<int> list(0);
-  }
-}
diff --git a/test/cctest/test-circular-queue.cc b/test/cctest/test-circular-queue.cc
index c4e5c4c..2861b1f 100644
--- a/test/cctest/test-circular-queue.cc
+++ b/test/cctest/test-circular-queue.cc
@@ -6,8 +6,6 @@
 #include "circular-queue-inl.h"
 #include "cctest.h"
 
-namespace i = v8::internal;
-
 using i::SamplingCircularQueue;
 
 
diff --git a/test/cctest/test-cpu-profiler.cc b/test/cctest/test-cpu-profiler.cc
index 9ff2a17..81c487d 100644
--- a/test/cctest/test-cpu-profiler.cc
+++ b/test/cctest/test-cpu-profiler.cc
@@ -7,8 +7,6 @@
 #include "cctest.h"
 #include "../include/v8-profiler.h"
 
-namespace i = v8::internal;
-
 using i::CodeEntry;
 using i::CpuProfile;
 using i::CpuProfiler;
diff --git a/test/cctest/test-debug.cc b/test/cctest/test-debug.cc
index 73b84b7..b7962de 100644
--- a/test/cctest/test-debug.cc
+++ b/test/cctest/test-debug.cc
@@ -2174,7 +2174,7 @@
   f = v8::Local<v8::Function>::Cast(env->Global()->Get(v8::String::New("f")));
   g = v8::Local<v8::Function>::Cast(env->Global()->Get(v8::String::New("g")));
 
-  // Chesk that a break point was hit when the script was run.
+  // Check that a break point was hit when the script was run.
   CHECK_EQ(1, break_point_hit_count);
   CHECK_EQ(0, StrLength(last_function_hit));
 
@@ -5844,6 +5844,7 @@
 
 
 TEST(DebuggerAgent) {
+  v8::V8::Initialize();
   i::Debugger* debugger = i::Isolate::Current()->debugger();
   // Make sure these ports is not used by other tests to allow tests to run in
   // parallel.
diff --git a/test/cctest/test-dictionary.cc b/test/cctest/test-dictionary.cc
new file mode 100644
index 0000000..15a854b
--- /dev/null
+++ b/test/cctest/test-dictionary.cc
@@ -0,0 +1,85 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "api.h"
+#include "debug.h"
+#include "execution.h"
+#include "factory.h"
+#include "macro-assembler.h"
+#include "objects.h"
+#include "global-handles.h"
+#include "cctest.h"
+
+using namespace v8::internal;
+
+TEST(ObjectHashTable) {
+  v8::HandleScope scope;
+  LocalContext context;
+  Handle<ObjectHashTable> table = FACTORY->NewObjectHashTable(23);
+  Handle<JSObject> a = FACTORY->NewJSArray(7);
+  Handle<JSObject> b = FACTORY->NewJSArray(11);
+  table = PutIntoObjectHashTable(table, a, b);
+  CHECK_EQ(table->NumberOfElements(), 1);
+  CHECK_EQ(table->Lookup(*a), *b);
+  CHECK_EQ(table->Lookup(*b), HEAP->undefined_value());
+
+  // Keys still have to be valid after objects were moved.
+  HEAP->CollectGarbage(NEW_SPACE);
+  CHECK_EQ(table->NumberOfElements(), 1);
+  CHECK_EQ(table->Lookup(*a), *b);
+  CHECK_EQ(table->Lookup(*b), HEAP->undefined_value());
+
+  // Keys that are overwritten should not change number of elements.
+  table = PutIntoObjectHashTable(table, a, FACTORY->NewJSArray(13));
+  CHECK_EQ(table->NumberOfElements(), 1);
+  CHECK_NE(table->Lookup(*a), *b);
+
+  // Keys mapped to undefined should be removed permanently.
+  table = PutIntoObjectHashTable(table, a, FACTORY->undefined_value());
+  CHECK_EQ(table->NumberOfElements(), 0);
+  CHECK_EQ(table->NumberOfDeletedElements(), 1);
+  CHECK_EQ(table->Lookup(*a), HEAP->undefined_value());
+
+  // Keys should map back to their respective values.
+  for (int i = 0; i < 100; i++) {
+    Handle<JSObject> key = FACTORY->NewJSArray(7);
+    Handle<JSObject> value = FACTORY->NewJSArray(11);
+    table = PutIntoObjectHashTable(table, key, value);
+    CHECK_EQ(table->NumberOfElements(), i + 1);
+    CHECK_NE(table->FindEntry(*key), ObjectHashTable::kNotFound);
+    CHECK_EQ(table->Lookup(*key), *value);
+  }
+
+  // Keys never added to the map should not be found.
+  for (int i = 0; i < 1000; i++) {
+    Handle<JSObject> o = FACTORY->NewJSArray(100);
+    CHECK_EQ(table->FindEntry(*o), ObjectHashTable::kNotFound);
+    CHECK_EQ(table->Lookup(*o), HEAP->undefined_value());
+  }
+}
diff --git a/test/cctest/test-func-name-inference.cc b/test/cctest/test-func-name-inference.cc
index 4d993af..bb930c8 100644
--- a/test/cctest/test-func-name-inference.cc
+++ b/test/cctest/test-func-name-inference.cc
@@ -361,3 +361,42 @@
   // Can't infer the function name statically.
   CheckFunctionName(script, "return 1", "obj.(anonymous function)");
 }
+
+
+TEST(GlobalAssignmentAndCall) {
+  InitializeVM();
+  v8::HandleScope scope;
+
+  v8::Handle<v8::Script> script = Compile(
+      "var Foo = function() {\n"
+      "  return 1;\n"
+      "}();\n"
+      "var Baz = Bar = function() {\n"
+      "  return 2;\n"
+      "}");
+  // The inferred name is empty, because this is an assignment of a result.
+  CheckFunctionName(script, "return 1", "");
+  // See MultipleAssignments test.
+  CheckFunctionName(script, "return 2", "Bar");
+}
+
+
+TEST(AssignmentAndCall) {
+  InitializeVM();
+  v8::HandleScope scope;
+
+  v8::Handle<v8::Script> script = Compile(
+      "(function Enclosing() {\n"
+      "  var Foo;\n"
+      "  Foo = function() {\n"
+      "    return 1;\n"
+      "  }();\n"
+      "  var Baz = Bar = function() {\n"
+      "    return 2;\n"
+      "  }\n"
+      "})();");
+  // The inferred name is empty, because this is an assignment of a result.
+  CheckFunctionName(script, "return 1", "");
+  // See MultipleAssignments test.
+  CheckFunctionName(script, "return 2", "Enclosing.Bar");
+}
diff --git a/test/cctest/test-heap-profiler.cc b/test/cctest/test-heap-profiler.cc
index 8675a01..143a23c 100644
--- a/test/cctest/test-heap-profiler.cc
+++ b/test/cctest/test-heap-profiler.cc
@@ -10,8 +10,6 @@
 #include "utils-inl.h"
 #include "../include/v8-profiler.h"
 
-namespace i = v8::internal;
-
 namespace {
 
 class NamedEntriesDetector {
@@ -87,7 +85,7 @@
       "var b2_1 = new B2(a2), b2_2 = new B2(a2);\n"
       "var c2 = new C2(a2);");
   const v8::HeapSnapshot* snapshot_env2 =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("env2"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("env2"));
   i::HeapSnapshot* i_snapshot_env2 =
       const_cast<i::HeapSnapshot*>(
           reinterpret_cast<const i::HeapSnapshot*>(snapshot_env2));
@@ -126,7 +124,7 @@
       "x = new X(new X(), new X());\n"
       "(function() { x.a.a = x.b; })();");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("sizes"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("sizes"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   const v8::HeapGraphNode* x =
       GetProperty(global, v8::HeapGraphEdge::kShortcut, "x");
@@ -157,7 +155,7 @@
       "function A() { }\n"
       "a = new A;");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("children"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("children"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   for (int i = 0, count = global->GetChildrenCount(); i < count; ++i) {
     const v8::HeapGraphEdge* prop = global->GetChild(i);
@@ -183,7 +181,7 @@
       "var anonymous = (function() { return function() { return 0; } })();\n"
       "compiled(1)");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("code"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("code"));
 
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   const v8::HeapGraphNode* compiled =
@@ -245,7 +243,7 @@
       "a = 1;    // a is Smi\n"
       "b = 2.5;  // b is HeapNumber");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("numbers"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("numbers"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   CHECK_EQ(NULL, GetProperty(global, v8::HeapGraphEdge::kShortcut, "a"));
   const v8::HeapGraphNode* b =
@@ -267,7 +265,7 @@
   global->SetInternalField(0, v8_num(17));
   global->SetInternalField(1, obj);
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("internals"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("internals"));
   const v8::HeapGraphNode* global_node = GetGlobalObject(snapshot);
   // The first reference will not present, because it's a Smi.
   CHECK_EQ(NULL, GetProperty(global_node, v8::HeapGraphEdge::kInternal, "0"));
@@ -294,12 +292,12 @@
       "var a = new A();\n"
       "var b = new B(a);");
   const v8::HeapSnapshot* snapshot1 =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("s1"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("s1"));
 
   HEAP->CollectAllGarbage(true);  // Enforce compaction.
 
   const v8::HeapSnapshot* snapshot2 =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("s2"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("s2"));
 
   const v8::HeapGraphNode* global1 = GetGlobalObject(snapshot1);
   const v8::HeapGraphNode* global2 = GetGlobalObject(snapshot2);
@@ -344,7 +342,7 @@
   v8::HandleScope scope;
   LocalContext env;
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("s"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("s"));
   const v8::HeapGraphNode* root1 = snapshot->GetRoot();
   const_cast<i::HeapSnapshot*>(reinterpret_cast<const i::HeapSnapshot*>(
       snapshot))->GetSortedEntriesList();
@@ -382,7 +380,7 @@
       "})();");
 
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("dominators"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("dominators"));
 
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   CHECK_NE(NULL, global);
@@ -465,7 +463,7 @@
       "var a = new A(" STRING_LITERAL_FOR_TEST ");\n"
       "var b = new B(a);");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("json"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("json"));
   TestJSONStream stream;
   snapshot->Serialize(&stream, v8::HeapSnapshot::kJSON);
   CHECK_GT(stream.size(), 0);
@@ -476,17 +474,17 @@
   // Verify that snapshot string is valid JSON.
   AsciiResource json_res(json);
   v8::Local<v8::String> json_string = v8::String::NewExternal(&json_res);
-  env->Global()->Set(v8::String::New("json_snapshot"), json_string);
+  env->Global()->Set(v8_str("json_snapshot"), json_string);
   v8::Local<v8::Value> snapshot_parse_result = CompileRun(
       "var parsed = JSON.parse(json_snapshot); true;");
   CHECK(!snapshot_parse_result.IsEmpty());
 
   // Verify that snapshot object has required fields.
   v8::Local<v8::Object> parsed_snapshot =
-      env->Global()->Get(v8::String::New("parsed"))->ToObject();
-  CHECK(parsed_snapshot->Has(v8::String::New("snapshot")));
-  CHECK(parsed_snapshot->Has(v8::String::New("nodes")));
-  CHECK(parsed_snapshot->Has(v8::String::New("strings")));
+      env->Global()->Get(v8_str("parsed"))->ToObject();
+  CHECK(parsed_snapshot->Has(v8_str("snapshot")));
+  CHECK(parsed_snapshot->Has(v8_str("nodes")));
+  CHECK(parsed_snapshot->Has(v8_str("strings")));
 
   // Get node and edge "member" offsets.
   v8::Local<v8::Value> meta_analysis_result = CompileRun(
@@ -538,12 +536,12 @@
   int string_obj_pos =
       static_cast<int>(string_obj_pos_val->ToNumber()->Value());
   v8::Local<v8::Object> nodes_array =
-      parsed_snapshot->Get(v8::String::New("nodes"))->ToObject();
+      parsed_snapshot->Get(v8_str("nodes"))->ToObject();
   int string_index = static_cast<int>(
       nodes_array->Get(string_obj_pos + 1)->ToNumber()->Value());
   CHECK_GT(string_index, 0);
   v8::Local<v8::Object> strings_array =
-      parsed_snapshot->Get(v8::String::New("strings"))->ToObject();
+      parsed_snapshot->Get(v8_str("strings"))->ToObject();
   v8::Local<v8::String> string = strings_array->Get(string_index)->ToString();
   v8::Local<v8::String> ref_string =
       CompileRun(STRING_LITERAL_FOR_TEST)->ToString();
@@ -557,7 +555,7 @@
   v8::HandleScope scope;
   LocalContext env;
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("abort"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("abort"));
   TestJSONStream stream(5);
   snapshot->Serialize(&stream, v8::HeapSnapshot::kJSON);
   CHECK_GT(stream.size(), 0);
@@ -570,7 +568,7 @@
   LocalContext env;
 
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("id"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("id"));
   const v8::HeapGraphNode* root = snapshot->GetRoot();
   CHECK_EQ(root, snapshot->GetNodeById(root->GetId()));
   for (int i = 0, count = root->GetChildrenCount(); i < count; ++i) {
@@ -611,7 +609,7 @@
   const int snapshots_count = v8::HeapProfiler::GetSnapshotsCount();
   TestActivityControl aborting_control(3);
   const v8::HeapSnapshot* no_snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("abort"),
+      v8::HeapProfiler::TakeSnapshot(v8_str("abort"),
                                      v8::HeapSnapshot::kFull,
                                      &aborting_control);
   CHECK_EQ(NULL, no_snapshot);
@@ -620,7 +618,7 @@
 
   TestActivityControl control(-1);  // Don't abort.
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("full"),
+      v8::HeapProfiler::TakeSnapshot(v8_str("full"),
                                      v8::HeapSnapshot::kFull,
                                      &control);
   CHECK_NE(NULL, snapshot);
@@ -730,7 +728,7 @@
   p_CCC.SetWrapperClassId(2);
   CHECK_EQ(0, TestRetainedObjectInfo::instances.length());
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("retained"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("retained"));
 
   CHECK_EQ(3, TestRetainedObjectInfo::instances.length());
   for (int i = 0; i < TestRetainedObjectInfo::instances.length(); ++i) {
@@ -774,12 +772,12 @@
   CHECK_EQ(0, v8::HeapProfiler::GetSnapshotsCount());
   v8::HeapProfiler::DeleteAllSnapshots();
   CHECK_EQ(0, v8::HeapProfiler::GetSnapshotsCount());
-  CHECK_NE(NULL, v8::HeapProfiler::TakeSnapshot(v8::String::New("1")));
+  CHECK_NE(NULL, v8::HeapProfiler::TakeSnapshot(v8_str("1")));
   CHECK_EQ(1, v8::HeapProfiler::GetSnapshotsCount());
   v8::HeapProfiler::DeleteAllSnapshots();
   CHECK_EQ(0, v8::HeapProfiler::GetSnapshotsCount());
-  CHECK_NE(NULL, v8::HeapProfiler::TakeSnapshot(v8::String::New("1")));
-  CHECK_NE(NULL, v8::HeapProfiler::TakeSnapshot(v8::String::New("2")));
+  CHECK_NE(NULL, v8::HeapProfiler::TakeSnapshot(v8_str("1")));
+  CHECK_NE(NULL, v8::HeapProfiler::TakeSnapshot(v8_str("2")));
   CHECK_EQ(2, v8::HeapProfiler::GetSnapshotsCount());
   v8::HeapProfiler::DeleteAllSnapshots();
   CHECK_EQ(0, v8::HeapProfiler::GetSnapshotsCount());
@@ -792,7 +790,7 @@
 
   CHECK_EQ(0, v8::HeapProfiler::GetSnapshotsCount());
   const v8::HeapSnapshot* s1 =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("1"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("1"));
   CHECK_NE(NULL, s1);
   CHECK_EQ(1, v8::HeapProfiler::GetSnapshotsCount());
   unsigned uid1 = s1->GetUid();
@@ -802,14 +800,14 @@
   CHECK_EQ(NULL, v8::HeapProfiler::FindSnapshot(uid1));
 
   const v8::HeapSnapshot* s2 =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("2"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("2"));
   CHECK_NE(NULL, s2);
   CHECK_EQ(1, v8::HeapProfiler::GetSnapshotsCount());
   unsigned uid2 = s2->GetUid();
   CHECK_NE(static_cast<int>(uid1), static_cast<int>(uid2));
   CHECK_EQ(s2, v8::HeapProfiler::FindSnapshot(uid2));
   const v8::HeapSnapshot* s3 =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("3"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("3"));
   CHECK_NE(NULL, s3);
   CHECK_EQ(2, v8::HeapProfiler::GetSnapshotsCount());
   unsigned uid3 = s3->GetUid();
@@ -832,7 +830,7 @@
   CompileRun("document = { URL:\"abcdefgh\" };");
 
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("document"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("document"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   CHECK_NE(NULL, global);
   CHECK_EQ("Object / abcdefgh",
@@ -848,7 +846,7 @@
   CompileRun(
       "this.__defineGetter__(\"document\", function() { throw new Error(); })");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("document"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("document"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   CHECK_NE(NULL, global);
   CHECK_EQ("Object",
@@ -866,7 +864,7 @@
       "URLWithException.prototype = { get URL() { throw new Error(); } };\n"
       "document = { URL: new URLWithException() };");
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("document"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("document"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   CHECK_NE(NULL, global);
   CHECK_EQ("Object",
@@ -879,7 +877,7 @@
   v8::HandleScope scope;
   LocalContext env;
   const v8::HeapSnapshot* snapshot =
-      v8::HeapProfiler::TakeSnapshot(v8::String::New("iteration"));
+      v8::HeapProfiler::TakeSnapshot(v8_str("iteration"));
   const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
   CHECK_NE(NULL, global);
   // Verify that we can find this object by iteration.
@@ -891,3 +889,115 @@
   }
   CHECK_EQ(1, count);
 }
+
+
+TEST(GetHeapValue) {
+  v8::HandleScope scope;
+  LocalContext env;
+
+  CompileRun("a = { s_prop: \'value\', n_prop: 0.1 };");
+  const v8::HeapSnapshot* snapshot =
+      v8::HeapProfiler::TakeSnapshot(v8_str("value"));
+  const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
+  CHECK(global->GetHeapValue()->IsObject());
+  v8::Local<v8::Object> js_global =
+      env->Global()->GetPrototype().As<v8::Object>();
+  CHECK(js_global == global->GetHeapValue());
+  const v8::HeapGraphNode* obj = GetProperty(
+      global, v8::HeapGraphEdge::kShortcut, "a");
+  CHECK(obj->GetHeapValue()->IsObject());
+  v8::Local<v8::Object> js_obj = js_global->Get(v8_str("a")).As<v8::Object>();
+  CHECK(js_obj == obj->GetHeapValue());
+  const v8::HeapGraphNode* s_prop =
+      GetProperty(obj, v8::HeapGraphEdge::kProperty, "s_prop");
+  v8::Local<v8::String> js_s_prop =
+      js_obj->Get(v8_str("s_prop")).As<v8::String>();
+  CHECK(js_s_prop == s_prop->GetHeapValue());
+  const v8::HeapGraphNode* n_prop =
+      GetProperty(obj, v8::HeapGraphEdge::kProperty, "n_prop");
+  v8::Local<v8::Number> js_n_prop =
+      js_obj->Get(v8_str("n_prop")).As<v8::Number>();
+  CHECK(js_n_prop == n_prop->GetHeapValue());
+}
+
+
+TEST(GetHeapValueForDeletedObject) {
+  v8::HandleScope scope;
+  LocalContext env;
+
+  // It is impossible to delete a global property, so we are about to delete a
+  // property of the "a" object. Also, the "p" object can't be an empty one
+  // because the empty object is static and isn't actually deleted.
+  CompileRun("a = { p: { r: {} } };");
+  const v8::HeapSnapshot* snapshot =
+      v8::HeapProfiler::TakeSnapshot(v8_str("snapshot"));
+  const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
+  const v8::HeapGraphNode* obj = GetProperty(
+      global, v8::HeapGraphEdge::kShortcut, "a");
+  const v8::HeapGraphNode* prop = GetProperty(
+      obj, v8::HeapGraphEdge::kProperty, "p");
+  {
+    // Perform the check inside a nested local scope to avoid creating a
+    // reference to the object we are deleting.
+    v8::HandleScope scope;
+    CHECK(prop->GetHeapValue()->IsObject());
+  }
+  CompileRun("delete a.p;");
+  CHECK(prop->GetHeapValue()->IsUndefined());
+}
+
+
+static int StringCmp(const char* ref, i::String* act) {
+  i::SmartPointer<char> s_act = act->ToCString();
+  int result = strcmp(ref, *s_act);
+  if (result != 0)
+    fprintf(stderr, "Expected: \"%s\", Actual: \"%s\"\n", ref, *s_act);
+  return result;
+}
+
+
+TEST(GetConstructorName) {
+  v8::HandleScope scope;
+  LocalContext env;
+
+  CompileRun(
+      "function Constructor1() {};\n"
+      "var obj1 = new Constructor1();\n"
+      "var Constructor2 = function() {};\n"
+      "var obj2 = new Constructor2();\n"
+      "var obj3 = {};\n"
+      "obj3.constructor = function Constructor3() {};\n"
+      "var obj4 = {};\n"
+      "// Slow properties\n"
+      "for (var i=0; i<2000; ++i) obj4[\"p\" + i] = i;\n"
+      "obj4.constructor = function Constructor4() {};\n"
+      "var obj5 = {};\n"
+      "var obj6 = {};\n"
+      "obj6.constructor = 6;");
+  v8::Local<v8::Object> js_global =
+      env->Global()->GetPrototype().As<v8::Object>();
+  v8::Local<v8::Object> obj1 = js_global->Get(v8_str("obj1")).As<v8::Object>();
+  i::Handle<i::JSObject> js_obj1 = v8::Utils::OpenHandle(*obj1);
+  CHECK_EQ(0, StringCmp(
+      "Constructor1", i::V8HeapExplorer::GetConstructorName(*js_obj1)));
+  v8::Local<v8::Object> obj2 = js_global->Get(v8_str("obj2")).As<v8::Object>();
+  i::Handle<i::JSObject> js_obj2 = v8::Utils::OpenHandle(*obj2);
+  CHECK_EQ(0, StringCmp(
+      "Constructor2", i::V8HeapExplorer::GetConstructorName(*js_obj2)));
+  v8::Local<v8::Object> obj3 = js_global->Get(v8_str("obj3")).As<v8::Object>();
+  i::Handle<i::JSObject> js_obj3 = v8::Utils::OpenHandle(*obj3);
+  CHECK_EQ(0, StringCmp(
+      "Constructor3", i::V8HeapExplorer::GetConstructorName(*js_obj3)));
+  v8::Local<v8::Object> obj4 = js_global->Get(v8_str("obj4")).As<v8::Object>();
+  i::Handle<i::JSObject> js_obj4 = v8::Utils::OpenHandle(*obj4);
+  CHECK_EQ(0, StringCmp(
+      "Constructor4", i::V8HeapExplorer::GetConstructorName(*js_obj4)));
+  v8::Local<v8::Object> obj5 = js_global->Get(v8_str("obj5")).As<v8::Object>();
+  i::Handle<i::JSObject> js_obj5 = v8::Utils::OpenHandle(*obj5);
+  CHECK_EQ(0, StringCmp(
+      "Object", i::V8HeapExplorer::GetConstructorName(*js_obj5)));
+  v8::Local<v8::Object> obj6 = js_global->Get(v8_str("obj6")).As<v8::Object>();
+  i::Handle<i::JSObject> js_obj6 = v8::Utils::OpenHandle(*obj6);
+  CHECK_EQ(0, StringCmp(
+      "Object", i::V8HeapExplorer::GetConstructorName(*js_obj6)));
+}
diff --git a/test/cctest/test-heap.cc b/test/cctest/test-heap.cc
index fac9f0a..11b8813 100644
--- a/test/cctest/test-heap.cc
+++ b/test/cctest/test-heap.cc
@@ -291,8 +291,8 @@
 
 
 TEST(GlobalHandles) {
-  GlobalHandles* global_handles = Isolate::Current()->global_handles();
   InitializeVM();
+  GlobalHandles* global_handles = Isolate::Current()->global_handles();
 
   Handle<Object> h1;
   Handle<Object> h2;
@@ -339,8 +339,8 @@
 
 
 TEST(WeakGlobalHandlesScavenge) {
-  GlobalHandles* global_handles = Isolate::Current()->global_handles();
   InitializeVM();
+  GlobalHandles* global_handles = Isolate::Current()->global_handles();
 
   WeakPointerCleared = false;
 
@@ -377,8 +377,8 @@
 
 
 TEST(WeakGlobalHandlesMark) {
-  GlobalHandles* global_handles = Isolate::Current()->global_handles();
   InitializeVM();
+  GlobalHandles* global_handles = Isolate::Current()->global_handles();
 
   WeakPointerCleared = false;
 
@@ -416,8 +416,8 @@
 }
 
 TEST(DeleteWeakGlobalHandle) {
-  GlobalHandles* global_handles = Isolate::Current()->global_handles();
   InitializeVM();
+  GlobalHandles* global_handles = Isolate::Current()->global_handles();
 
   WeakPointerCleared = false;
 
diff --git a/test/cctest/test-list.cc b/test/cctest/test-list.cc
index e20ee8a..7520b05 100644
--- a/test/cctest/test-list.cc
+++ b/test/cctest/test-list.cc
@@ -1,4 +1,4 @@
-// Copyright 2009 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -138,3 +138,14 @@
   list.Clear();
   CHECK_EQ(0, list.length());
 }
+
+
+TEST(DeleteEmpty) {
+  {
+    List<int>* list = new List<int>(0);
+    delete list;
+  }
+  {
+    List<int> list(0);
+  }
+}
diff --git a/test/cctest/test-lockers.cc b/test/cctest/test-lockers.cc
index 2b184e9..d61fde2 100644
--- a/test/cctest/test-lockers.cc
+++ b/test/cctest/test-lockers.cc
@@ -54,10 +54,6 @@
 using ::v8::Value;
 using ::v8::V8;
 
-namespace i = ::i;
-
-
-
 
 // Migrating an isolate
 class KangarooThread : public v8::internal::Thread {
diff --git a/test/cctest/test-log-stack-tracer.cc b/test/cctest/test-log-stack-tracer.cc
index 2bcb3fe..f536e6b 100644
--- a/test/cctest/test-log-stack-tracer.cc
+++ b/test/cctest/test-log-stack-tracer.cc
@@ -54,8 +54,6 @@
 using v8::internal::StackTracer;
 using v8::internal::TickSample;
 
-namespace i = v8::internal;
-
 
 static v8::Persistent<v8::Context> env;
 
diff --git a/test/cctest/test-log.cc b/test/cctest/test-log.cc
index 262e7bb..dfbc733 100644
--- a/test/cctest/test-log.cc
+++ b/test/cctest/test-log.cc
@@ -23,8 +23,6 @@
 using v8::internal::Logger;
 using v8::internal::StrLength;
 
-namespace i = v8::internal;
-
 namespace {
 
 class ScopedLoggerInitializer {
diff --git a/test/cctest/test-parsing.cc b/test/cctest/test-parsing.cc
index 96a181d..8b6afdc 100755
--- a/test/cctest/test-parsing.cc
+++ b/test/cctest/test-parsing.cc
@@ -40,9 +40,7 @@
 #include "preparser.h"
 #include "cctest.h"
 
-namespace i = ::v8::internal;
-
-TEST(KeywordMatcher) {
+TEST(ScanKeywords) {
   struct KeywordToken {
     const char* keyword;
     i::Token::Value token;
@@ -50,90 +48,64 @@
 
   static const KeywordToken keywords[] = {
 #define KEYWORD(t, s, d) { s, i::Token::t },
-#define IGNORE(t, s, d)  /* */
-      TOKEN_LIST(IGNORE, KEYWORD, IGNORE)
+      TOKEN_LIST(IGNORE_TOKEN, KEYWORD)
 #undef KEYWORD
       { NULL, i::Token::IDENTIFIER }
   };
 
-  static const char* future_keywords[] = {
-#define FUTURE(t, s, d) s,
-      TOKEN_LIST(IGNORE, IGNORE, FUTURE)
-#undef FUTURE
-#undef IGNORE
-      NULL
-  };
-
   KeywordToken key_token;
+  i::UnicodeCache unicode_cache;
+  i::byte buffer[32];
   for (int i = 0; (key_token = keywords[i]).keyword != NULL; i++) {
-    i::KeywordMatcher matcher;
-    const char* keyword = key_token.keyword;
-    int length = i::StrLength(keyword);
-    for (int j = 0; j < length; j++) {
-      if (key_token.token == i::Token::INSTANCEOF && j == 2) {
-        // "in" is a prefix of "instanceof". It's the only keyword
-        // that is a prefix of another.
-        CHECK_EQ(i::Token::IN, matcher.token());
-      } else {
-        CHECK_EQ(i::Token::IDENTIFIER, matcher.token());
-      }
-      matcher.AddChar(keyword[j]);
+    const i::byte* keyword =
+        reinterpret_cast<const i::byte*>(key_token.keyword);
+    int length = i::StrLength(key_token.keyword);
+    CHECK(static_cast<int>(sizeof(buffer)) >= length);
+    {
+      i::Utf8ToUC16CharacterStream stream(keyword, length);
+      i::JavaScriptScanner scanner(&unicode_cache);
+      // The scanner should parse 'let' as Token::LET for this test.
+      scanner.SetHarmonyBlockScoping(true);
+      scanner.Initialize(&stream);
+      CHECK_EQ(key_token.token, scanner.Next());
+      CHECK_EQ(i::Token::EOS, scanner.Next());
     }
-    CHECK_EQ(key_token.token, matcher.token());
-    // Adding more characters will make keyword matching fail.
-    matcher.AddChar('z');
-    CHECK_EQ(i::Token::IDENTIFIER, matcher.token());
-    // Adding a keyword later will not make it match again.
-    matcher.AddChar('i');
-    matcher.AddChar('f');
-    CHECK_EQ(i::Token::IDENTIFIER, matcher.token());
-  }
-
-  // Future keywords are not recognized.
-  const char* future_keyword;
-  for (int i = 0; (future_keyword = future_keywords[i]) != NULL; i++) {
-    i::KeywordMatcher matcher;
-    int length = i::StrLength(future_keyword);
-    for (int j = 0; j < length; j++) {
-      matcher.AddChar(future_keyword[j]);
+    // Removing characters will make keyword matching fail.
+    {
+      i::Utf8ToUC16CharacterStream stream(keyword, length - 1);
+      i::JavaScriptScanner scanner(&unicode_cache);
+      scanner.Initialize(&stream);
+      CHECK_EQ(i::Token::IDENTIFIER, scanner.Next());
+      CHECK_EQ(i::Token::EOS, scanner.Next());
     }
-    CHECK_EQ(i::Token::IDENTIFIER, matcher.token());
+    // Adding characters will make keyword matching fail.
+    static const char chars_to_append[] = { 'z', '0', '_' };
+    for (int j = 0; j < static_cast<int>(ARRAY_SIZE(chars_to_append)); ++j) {
+      memmove(buffer, keyword, length);
+      buffer[length] = chars_to_append[j];
+      i::Utf8ToUC16CharacterStream stream(buffer, length + 1);
+      i::JavaScriptScanner scanner(&unicode_cache);
+      scanner.Initialize(&stream);
+      CHECK_EQ(i::Token::IDENTIFIER, scanner.Next());
+      CHECK_EQ(i::Token::EOS, scanner.Next());
+    }
+    // Replacing characters will make keyword matching fail.
+    {
+      memmove(buffer, keyword, length);
+      buffer[length - 1] = '_';
+      i::Utf8ToUC16CharacterStream stream(buffer, length);
+      i::JavaScriptScanner scanner(&unicode_cache);
+      scanner.Initialize(&stream);
+      CHECK_EQ(i::Token::IDENTIFIER, scanner.Next());
+      CHECK_EQ(i::Token::EOS, scanner.Next());
+    }
   }
-
-  // Zero isn't ignored at first.
-  i::KeywordMatcher bad_start;
-  bad_start.AddChar(0);
-  CHECK_EQ(i::Token::IDENTIFIER, bad_start.token());
-  bad_start.AddChar('i');
-  bad_start.AddChar('f');
-  CHECK_EQ(i::Token::IDENTIFIER, bad_start.token());
-
-  // Zero isn't ignored at end.
-  i::KeywordMatcher bad_end;
-  bad_end.AddChar('i');
-  bad_end.AddChar('f');
-  CHECK_EQ(i::Token::IF, bad_end.token());
-  bad_end.AddChar(0);
-  CHECK_EQ(i::Token::IDENTIFIER, bad_end.token());
-
-  // Case isn't ignored.
-  i::KeywordMatcher bad_case;
-  bad_case.AddChar('i');
-  bad_case.AddChar('F');
-  CHECK_EQ(i::Token::IDENTIFIER, bad_case.token());
-
-  // If we mark it as failure, continuing won't help.
-  i::KeywordMatcher full_stop;
-  full_stop.AddChar('i');
-  CHECK_EQ(i::Token::IDENTIFIER, full_stop.token());
-  full_stop.Fail();
-  CHECK_EQ(i::Token::IDENTIFIER, full_stop.token());
-  full_stop.AddChar('f');
-  CHECK_EQ(i::Token::IDENTIFIER, full_stop.token());
 }
 
 
 TEST(ScanHTMLEndComments) {
+  v8::V8::Initialize();
+
   // Regression test. See:
   //    http://code.google.com/p/chromium/issues/detail?id=53548
   // Tests that --> is correctly interpreted as comment-to-end-of-line if there
@@ -263,6 +235,8 @@
 
 
 TEST(StandAlonePreParser) {
+  v8::V8::Initialize();
+
   int marker;
   i::Isolate::Current()->stack_guard()->SetStackLimit(
       reinterpret_cast<uintptr_t>(&marker) - 128 * 1024);
@@ -299,6 +273,8 @@
 
 
 TEST(RegressChromium62639) {
+  v8::V8::Initialize();
+
   int marker;
   i::Isolate::Current()->stack_guard()->SetStackLimit(
       reinterpret_cast<uintptr_t>(&marker) - 128 * 1024);
@@ -313,13 +289,15 @@
   i::Utf8ToUC16CharacterStream stream(reinterpret_cast<const i::byte*>(program),
                                       static_cast<unsigned>(strlen(program)));
   i::ScriptDataImpl* data =
-      i::ParserApi::PreParse(&stream, NULL);
+      i::ParserApi::PreParse(&stream, NULL, false);
   CHECK(data->HasError());
   delete data;
 }
 
 
 TEST(Regress928) {
+  v8::V8::Initialize();
+
   // Preparsing didn't consider the catch clause of a try statement
   // as with-content, which made it assume that a function inside
   // the block could be lazily compiled, and an extra, unexpected,
@@ -335,7 +313,7 @@
   i::Utf8ToUC16CharacterStream stream(reinterpret_cast<const i::byte*>(program),
                                       static_cast<unsigned>(strlen(program)));
   i::ScriptDataImpl* data =
-      i::ParserApi::PartialPreParse(&stream, NULL);
+      i::ParserApi::PartialPreParse(&stream, NULL, false);
   CHECK(!data->HasError());
 
   data->Initialize();
@@ -360,6 +338,8 @@
 
 
 TEST(PreParseOverflow) {
+  v8::V8::Initialize();
+
   int marker;
   i::Isolate::Current()->stack_guard()->SetStackLimit(
       reinterpret_cast<uintptr_t>(&marker) - 128 * 1024);
@@ -610,6 +590,8 @@
 }
 
 TEST(StreamScanner) {
+  v8::V8::Initialize();
+
   const char* str1 = "{ foo get for : */ <- \n\n /*foo*/ bib";
   i::Utf8ToUC16CharacterStream stream1(reinterpret_cast<const i::byte*>(str1),
                                        static_cast<unsigned>(strlen(str1)));
@@ -690,6 +672,8 @@
 
 
 TEST(RegExpScanning) {
+  v8::V8::Initialize();
+
   // RegExp token with added garbage at the end. The scanner should only
   // scan the RegExp until the terminating slash just before "flipperwald".
   TestScanRegExp("/b/flipperwald", "b");
diff --git a/test/cctest/test-profile-generator.cc b/test/cctest/test-profile-generator.cc
index 6d30443..250ebd4 100644
--- a/test/cctest/test-profile-generator.cc
+++ b/test/cctest/test-profile-generator.cc
@@ -7,8 +7,6 @@
 #include "cctest.h"
 #include "../include/v8-profiler.h"
 
-namespace i = v8::internal;
-
 using i::CodeEntry;
 using i::CodeMap;
 using i::CpuProfile;
diff --git a/test/cctest/test-serialize.cc b/test/cctest/test-serialize.cc
index 730d72a..8e85444 100644
--- a/test/cctest/test-serialize.cc
+++ b/test/cctest/test-serialize.cc
@@ -99,10 +99,10 @@
 
 
 TEST(ExternalReferenceEncoder) {
-  OS::Setup();
   Isolate* isolate = i::Isolate::Current();
   isolate->stats_table()->SetCounterFunction(counter_function);
-  HEAP->Setup(false);
+  v8::V8::Initialize();
+
   ExternalReferenceEncoder encoder;
   CHECK_EQ(make_code(BUILTIN, Builtins::kArrayCode),
            Encode(encoder, Builtins::kArrayCode));
@@ -139,10 +139,10 @@
 
 
 TEST(ExternalReferenceDecoder) {
-  OS::Setup();
   Isolate* isolate = i::Isolate::Current();
   isolate->stats_table()->SetCounterFunction(counter_function);
-  HEAP->Setup(false);
+  v8::V8::Initialize();
+
   ExternalReferenceDecoder decoder;
   CHECK_EQ(AddressOf(Builtins::kArrayCode),
            decoder.Decode(make_code(BUILTIN, Builtins::kArrayCode)));
@@ -459,7 +459,9 @@
       CHECK(root->IsString());
     }
     v8::HandleScope handle_scope;
-    Handle<Object>root_handle(root);
+    Handle<Object> root_handle(root);
+
+    ReserveSpaceForPartialSnapshot(file_name);
 
     Object* root2;
     {
@@ -542,7 +544,9 @@
       CHECK(root->IsContext());
     }
     v8::HandleScope handle_scope;
-    Handle<Object>root_handle(root);
+    Handle<Object> root_handle(root);
+
+    ReserveSpaceForPartialSnapshot(file_name);
 
     Object* root2;
     {
diff --git a/test/cctest/test-spaces.cc b/test/cctest/test-spaces.cc
index de0c41e..0f22ce1 100644
--- a/test/cctest/test-spaces.cc
+++ b/test/cctest/test-spaces.cc
@@ -91,46 +91,74 @@
 }
 
 
+namespace v8 {
+namespace internal {
+
+// Temporarily sets a given allocator in an isolate.
+class TestMemoryAllocatorScope {
+ public:
+  TestMemoryAllocatorScope(Isolate* isolate, MemoryAllocator* allocator)
+      : isolate_(isolate),
+        old_allocator_(isolate->memory_allocator_) {
+    isolate->memory_allocator_ = allocator;
+  }
+
+  ~TestMemoryAllocatorScope() {
+    isolate_->memory_allocator_ = old_allocator_;
+  }
+
+ private:
+  Isolate* isolate_;
+  MemoryAllocator* old_allocator_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestMemoryAllocatorScope);
+};
+
+} }  // namespace v8::internal
+
+
 TEST(MemoryAllocator) {
   OS::Setup();
   Isolate* isolate = Isolate::Current();
-  CHECK(HEAP->ConfigureHeapDefault());
-  CHECK(isolate->memory_allocator()->Setup(HEAP->MaxReserved(),
-                                           HEAP->MaxExecutableSize()));
+  isolate->InitializeLoggingAndCounters();
+  Heap* heap = isolate->heap();
+  CHECK(heap->ConfigureHeapDefault());
+  MemoryAllocator* memory_allocator = new MemoryAllocator(isolate);
+  CHECK(memory_allocator->Setup(heap->MaxReserved(),
+                                heap->MaxExecutableSize()));
+  TestMemoryAllocatorScope test_scope(isolate, memory_allocator);
 
-  OldSpace faked_space(HEAP,
-                       HEAP->MaxReserved(),
+  OldSpace faked_space(heap,
+                       heap->MaxReserved(),
                        OLD_POINTER_SPACE,
                        NOT_EXECUTABLE);
   int total_pages = 0;
   int requested = MemoryAllocator::kPagesPerChunk;
   int allocated;
   // If we request n pages, we should get n or n - 1.
-  Page* first_page =
-      isolate->memory_allocator()->AllocatePages(
-          requested, &allocated, &faked_space);
+  Page* first_page = memory_allocator->AllocatePages(
+      requested, &allocated, &faked_space);
   CHECK(first_page->is_valid());
   CHECK(allocated == requested || allocated == requested - 1);
   total_pages += allocated;
 
   Page* last_page = first_page;
   for (Page* p = first_page; p->is_valid(); p = p->next_page()) {
-    CHECK(isolate->memory_allocator()->IsPageInSpace(p, &faked_space));
+    CHECK(memory_allocator->IsPageInSpace(p, &faked_space));
     last_page = p;
   }
 
   // Again, we should get n or n - 1 pages.
-  Page* others =
-      isolate->memory_allocator()->AllocatePages(
-          requested, &allocated, &faked_space);
+  Page* others = memory_allocator->AllocatePages(
+      requested, &allocated, &faked_space);
   CHECK(others->is_valid());
   CHECK(allocated == requested || allocated == requested - 1);
   total_pages += allocated;
 
-  isolate->memory_allocator()->SetNextPage(last_page, others);
+  memory_allocator->SetNextPage(last_page, others);
   int page_count = 0;
   for (Page* p = first_page; p->is_valid(); p = p->next_page()) {
-    CHECK(isolate->memory_allocator()->IsPageInSpace(p, &faked_space));
+    CHECK(memory_allocator->IsPageInSpace(p, &faked_space));
     page_count++;
   }
   CHECK(total_pages == page_count);
@@ -141,34 +169,39 @@
   // Freeing pages at the first chunk starting at or after the second page
   // should free the entire second chunk.  It will return the page it was passed
   // (since the second page was in the first chunk).
-  Page* free_return = isolate->memory_allocator()->FreePages(second_page);
+  Page* free_return = memory_allocator->FreePages(second_page);
   CHECK(free_return == second_page);
-  isolate->memory_allocator()->SetNextPage(first_page, free_return);
+  memory_allocator->SetNextPage(first_page, free_return);
 
   // Freeing pages in the first chunk starting at the first page should free
   // the first chunk and return an invalid page.
-  Page* invalid_page = isolate->memory_allocator()->FreePages(first_page);
+  Page* invalid_page = memory_allocator->FreePages(first_page);
   CHECK(!invalid_page->is_valid());
 
-  isolate->memory_allocator()->TearDown();
+  memory_allocator->TearDown();
+  delete memory_allocator;
 }
 
 
 TEST(NewSpace) {
   OS::Setup();
-  CHECK(HEAP->ConfigureHeapDefault());
-  CHECK(Isolate::Current()->memory_allocator()->Setup(
-      HEAP->MaxReserved(), HEAP->MaxExecutableSize()));
+  Isolate* isolate = Isolate::Current();
+  isolate->InitializeLoggingAndCounters();
+  Heap* heap = isolate->heap();
+  CHECK(heap->ConfigureHeapDefault());
+  MemoryAllocator* memory_allocator = new MemoryAllocator(isolate);
+  CHECK(memory_allocator->Setup(heap->MaxReserved(),
+                                heap->MaxExecutableSize()));
+  TestMemoryAllocatorScope test_scope(isolate, memory_allocator);
 
-  NewSpace new_space(HEAP);
+  NewSpace new_space(heap);
 
   void* chunk =
-      Isolate::Current()->memory_allocator()->ReserveInitialChunk(
-          4 * HEAP->ReservedSemiSpaceSize());
+      memory_allocator->ReserveInitialChunk(4 * heap->ReservedSemiSpaceSize());
   CHECK(chunk != NULL);
   Address start = RoundUp(static_cast<Address>(chunk),
-                          2 * HEAP->ReservedSemiSpaceSize());
-  CHECK(new_space.Setup(start, 2 * HEAP->ReservedSemiSpaceSize()));
+                          2 * heap->ReservedSemiSpaceSize());
+  CHECK(new_space.Setup(start, 2 * heap->ReservedSemiSpaceSize()));
   CHECK(new_space.HasBeenSetup());
 
   while (new_space.Available() >= Page::kMaxHeapObjectSize) {
@@ -178,28 +211,33 @@
   }
 
   new_space.TearDown();
-  Isolate::Current()->memory_allocator()->TearDown();
+  memory_allocator->TearDown();
+  delete memory_allocator;
 }
 
 
 TEST(OldSpace) {
   OS::Setup();
-  CHECK(HEAP->ConfigureHeapDefault());
-  CHECK(Isolate::Current()->memory_allocator()->Setup(
-      HEAP->MaxReserved(), HEAP->MaxExecutableSize()));
+  Isolate* isolate = Isolate::Current();
+  isolate->InitializeLoggingAndCounters();
+  Heap* heap = isolate->heap();
+  CHECK(heap->ConfigureHeapDefault());
+  MemoryAllocator* memory_allocator = new MemoryAllocator(isolate);
+  CHECK(memory_allocator->Setup(heap->MaxReserved(),
+                                heap->MaxExecutableSize()));
+  TestMemoryAllocatorScope test_scope(isolate, memory_allocator);
 
-  OldSpace* s = new OldSpace(HEAP,
-                             HEAP->MaxOldGenerationSize(),
+  OldSpace* s = new OldSpace(heap,
+                             heap->MaxOldGenerationSize(),
                              OLD_POINTER_SPACE,
                              NOT_EXECUTABLE);
   CHECK(s != NULL);
 
-  void* chunk =
-      Isolate::Current()->memory_allocator()->ReserveInitialChunk(
-          4 * HEAP->ReservedSemiSpaceSize());
+  void* chunk = memory_allocator->ReserveInitialChunk(
+      4 * heap->ReservedSemiSpaceSize());
   CHECK(chunk != NULL);
   Address start = static_cast<Address>(chunk);
-  size_t size = RoundUp(start, 2 * HEAP->ReservedSemiSpaceSize()) - start;
+  size_t size = RoundUp(start, 2 * heap->ReservedSemiSpaceSize()) - start;
 
   CHECK(s->Setup(start, size));
 
@@ -209,13 +247,13 @@
 
   s->TearDown();
   delete s;
-  Isolate::Current()->memory_allocator()->TearDown();
+  memory_allocator->TearDown();
+  delete memory_allocator;
 }
 
 
 TEST(LargeObjectSpace) {
-  OS::Setup();
-  CHECK(HEAP->Setup(false));
+  v8::V8::Initialize();
 
   LargeObjectSpace* lo = HEAP->lo_space();
   CHECK(lo != NULL);
@@ -247,9 +285,4 @@
   CHECK(!lo->IsEmpty());
 
   CHECK(lo->AllocateRaw(lo_size)->IsFailure());
-
-  lo->TearDown();
-  delete lo;
-
-  Isolate::Current()->memory_allocator()->TearDown();
 }
diff --git a/test/cctest/test-strings.cc b/test/cctest/test-strings.cc
index 4d9b264..17020a3 100644
--- a/test/cctest/test-strings.cc
+++ b/test/cctest/test-strings.cc
@@ -430,8 +430,7 @@
     "  return 0;"
     "};"
     "test()";
-  CHECK_EQ(0,
-           v8::Script::Compile(v8::String::New(source))->Run()->Int32Value());
+  CHECK_EQ(0, CompileRun(source)->Int32Value());
 }
 
 
@@ -481,3 +480,52 @@
     }
   }
 }
+
+
+TEST(SliceFromCons) {
+  FLAG_string_slices = true;
+  InitializeVM();
+  v8::HandleScope scope;
+  Handle<String> string =
+      FACTORY->NewStringFromAscii(CStrVector("parentparentparent"));
+  Handle<String> parent = FACTORY->NewConsString(string, string);
+  CHECK(parent->IsConsString());
+  CHECK(!parent->IsFlat());
+  Handle<String> slice = FACTORY->NewSubString(parent, 1, 25);
+  // After slicing, the original string becomes a flat cons.
+  CHECK(parent->IsFlat());
+  CHECK(slice->IsSlicedString());
+  CHECK_EQ(SlicedString::cast(*slice)->parent(),
+           ConsString::cast(*parent)->first());
+  CHECK(SlicedString::cast(*slice)->parent()->IsSeqString());
+  CHECK(slice->IsFlat());
+}
+
+
+TEST(TrivialSlice) {
+  // This tests whether a slice that contains the entire parent string
+  // actually creates a new string (it should not).
+  FLAG_string_slices = true;
+  InitializeVM();
+  HandleScope scope;
+  v8::Local<v8::Value> result;
+  Handle<String> string;
+  const char* init = "var str = 'abcdefghijklmnopqrstuvwxyz';";
+  const char* check = "str.slice(0,26)";
+  const char* crosscheck = "str.slice(1,25)";
+
+  CompileRun(init);
+
+  result = CompileRun(check);
+  CHECK(result->IsString());
+  string = v8::Utils::OpenHandle(v8::String::Cast(*result));
+  CHECK(!string->IsSlicedString());
+
+  string = FACTORY->NewSubString(string, 0, 26);
+  CHECK(!string->IsSlicedString());
+  result = CompileRun(crosscheck);
+  CHECK(result->IsString());
+  string = v8::Utils::OpenHandle(v8::String::Cast(*result));
+  CHECK(string->IsSlicedString());
+  CHECK_EQ("bcdefghijklmnopqrstuvwxy", *(string->ToCString()));
+}
diff --git a/test/cctest/test-unbound-queue.cc b/test/cctest/test-unbound-queue.cc
index df5509e..3dc87ae 100644
--- a/test/cctest/test-unbound-queue.cc
+++ b/test/cctest/test-unbound-queue.cc
@@ -6,8 +6,6 @@
 #include "unbound-queue-inl.h"
 #include "cctest.h"
 
-namespace i = v8::internal;
-
 using i::UnboundQueue;
 
 
diff --git a/test/cctest/test-weakmaps.cc b/test/cctest/test-weakmaps.cc
new file mode 100644
index 0000000..db4db25
--- /dev/null
+++ b/test/cctest/test-weakmaps.cc
@@ -0,0 +1,149 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "global-handles.h"
+#include "snapshot.h"
+#include "cctest.h"
+
+using namespace v8::internal;
+
+
+static Handle<JSWeakMap> AllocateJSWeakMap() {
+  Handle<Map> map = FACTORY->NewMap(JS_WEAK_MAP_TYPE, JSWeakMap::kSize);
+  Handle<JSObject> weakmap_obj = FACTORY->NewJSObjectFromMap(map);
+  Handle<JSWeakMap> weakmap(JSWeakMap::cast(*weakmap_obj));
+  // Do not use handles for the hash table, it would make entries strong.
+  Object* table_obj = ObjectHashTable::Allocate(1)->ToObjectChecked();
+  ObjectHashTable* table = ObjectHashTable::cast(table_obj);
+  weakmap->set_table(table);
+  weakmap->set_next(Smi::FromInt(0));
+  return weakmap;
+}
+
+static void PutIntoWeakMap(Handle<JSWeakMap> weakmap,
+                           Handle<JSObject> key,
+                           int value) {
+  Handle<ObjectHashTable> table = PutIntoObjectHashTable(
+      Handle<ObjectHashTable>(weakmap->table()),
+      Handle<JSObject>(JSObject::cast(*key)),
+      Handle<Smi>(Smi::FromInt(value)));
+  weakmap->set_table(*table);
+}
+
+static int NumberOfWeakCalls = 0;
+static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
+  ASSERT(id == reinterpret_cast<void*>(1234));
+  NumberOfWeakCalls++;
+  handle.Dispose();
+}
+
+
+TEST(Weakness) {
+  LocalContext context;
+  v8::HandleScope scope;
+  Handle<JSWeakMap> weakmap = AllocateJSWeakMap();
+  GlobalHandles* global_handles = Isolate::Current()->global_handles();
+
+  // Keep global reference to the key.
+  Handle<Object> key;
+  {
+    v8::HandleScope scope;
+    Handle<Map> map = FACTORY->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
+    Handle<JSObject> object = FACTORY->NewJSObjectFromMap(map);
+    key = global_handles->Create(*object);
+  }
+  CHECK(!global_handles->IsWeak(key.location()));
+
+  // Put entry into weak map.
+  {
+    v8::HandleScope scope;
+    PutIntoWeakMap(weakmap, Handle<JSObject>(JSObject::cast(*key)), 23);
+  }
+  CHECK_EQ(1, weakmap->table()->NumberOfElements());
+
+  // Force a full GC.
+  HEAP->CollectAllGarbage(false);
+  CHECK_EQ(0, NumberOfWeakCalls);
+  CHECK_EQ(1, weakmap->table()->NumberOfElements());
+  CHECK_EQ(0, weakmap->table()->NumberOfDeletedElements());
+
+  // Make the global reference to the key weak.
+  {
+    v8::HandleScope scope;
+    global_handles->MakeWeak(key.location(),
+                             reinterpret_cast<void*>(1234),
+                             &WeakPointerCallback);
+  }
+  CHECK(global_handles->IsWeak(key.location()));
+
+  // Force a full GC.
+  // Perform two consecutive GCs because the first one will only clear
+  // weak references whereas the second one will also clear weak maps.
+  HEAP->CollectAllGarbage(false);
+  CHECK_EQ(1, NumberOfWeakCalls);
+  CHECK_EQ(1, weakmap->table()->NumberOfElements());
+  CHECK_EQ(0, weakmap->table()->NumberOfDeletedElements());
+  HEAP->CollectAllGarbage(false);
+  CHECK_EQ(1, NumberOfWeakCalls);
+  CHECK_EQ(0, weakmap->table()->NumberOfElements());
+  CHECK_EQ(1, weakmap->table()->NumberOfDeletedElements());
+}
+
+
+TEST(Shrinking) {
+  LocalContext context;
+  v8::HandleScope scope;
+  Handle<JSWeakMap> weakmap = AllocateJSWeakMap();
+
+  // Check initial capacity.
+  CHECK_EQ(32, weakmap->table()->Capacity());
+
+  // Fill up weak map to trigger capacity change.
+  {
+    v8::HandleScope scope;
+    Handle<Map> map = FACTORY->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
+    for (int i = 0; i < 32; i++) {
+      Handle<JSObject> object = FACTORY->NewJSObjectFromMap(map);
+      PutIntoWeakMap(weakmap, object, i);
+    }
+  }
+
+  // Check increased capacity.
+  CHECK_EQ(128, weakmap->table()->Capacity());
+
+  // Force a full GC.
+  CHECK_EQ(32, weakmap->table()->NumberOfElements());
+  CHECK_EQ(0, weakmap->table()->NumberOfDeletedElements());
+  HEAP->CollectAllGarbage(false);
+  CHECK_EQ(0, weakmap->table()->NumberOfElements());
+  CHECK_EQ(32, weakmap->table()->NumberOfDeletedElements());
+
+  // Check shrunk capacity.
+  CHECK_EQ(32, weakmap->table()->Capacity());
+}
diff --git a/test/cctest/testcfg.py b/test/cctest/testcfg.py
index a137275..b2eabc4 100644
--- a/test/cctest/testcfg.py
+++ b/test/cctest/testcfg.py
@@ -48,7 +48,11 @@
     return self.path[-1]
 
   def BuildCommand(self, name):
-    serialization_file = join('obj', 'test', self.mode, 'serdes')
+    serialization_file = ''
+    if exists(join(self.context.buildspace, 'obj', 'test', self.mode)):
+      serialization_file = join('obj', 'test', self.mode, 'serdes')
+    else:
+      serialization_file = join('obj', 'serdes')
     serialization_file += '_' + self.GetName()
     serialization_file = join(self.context.buildspace, serialization_file)
     serialization_file += ''.join(self.variant_flags).replace('-', '_')
@@ -78,10 +82,15 @@
     return ['cctests']
 
   def ListTests(self, current_path, path, mode, variant_flags):
-    executable = join('obj', 'test', mode, 'cctest')
+    executable = 'cctest'
     if utils.IsWindows():
       executable += '.exe'
     executable = join(self.context.buildspace, executable)
+    if not exists(executable):
+      executable = join('obj', 'test', mode, 'cctest')
+      if utils.IsWindows():
+        executable += '.exe'
+      executable = join(self.context.buildspace, executable)
     output = test.Execute([executable, '--list'], self.context)
     if output.exit_code != 0:
       print output.stdout
diff --git a/test/es5conform/testcfg.py b/test/es5conform/testcfg.py
index af74b8c..b6a17d9 100644
--- a/test/es5conform/testcfg.py
+++ b/test/es5conform/testcfg.py
@@ -97,7 +97,7 @@
     return tests
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     status_file = join(self.root, 'es5conform.status')
diff --git a/test/message/testcfg.py b/test/message/testcfg.py
index aabbfef..af467e6 100644
--- a/test/message/testcfg.py
+++ b/test/message/testcfg.py
@@ -125,7 +125,7 @@
     return result
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     status_file = join(self.root, 'message.status')
diff --git a/test/mjsunit/assert-opt-and-deopt.js b/test/mjsunit/assert-opt-and-deopt.js
index f589868..c9adb5b 100644
--- a/test/mjsunit/assert-opt-and-deopt.js
+++ b/test/mjsunit/assert-opt-and-deopt.js
@@ -54,7 +54,7 @@
  * that you later want to track de/optimizations for. It is necessary because
  * tests are sometimes executed several times in a row, and you want to
  * disregard counts from previous runs.
- */ 
+ */
 OptTracker.prototype.CheckpointOptCount = function(func) {
   this.opt_counts_[func] = %GetOptimizationCount(func);
 };
@@ -148,7 +148,7 @@
 tracker.AssertDeoptHappened(f, false);
 tracker.AssertDeoptCount(f, 0);
 
-for (var i = 0; i < 2; i++) f(1);
+f(1);
 
 tracker.AssertOptCount(f, 0);
 tracker.AssertIsOptimized(f, false);
diff --git a/test/mjsunit/bugs/harmony/debug-blockscopes.js b/test/mjsunit/bugs/harmony/debug-blockscopes.js
new file mode 100644
index 0000000..a407c53
--- /dev/null
+++ b/test/mjsunit/bugs/harmony/debug-blockscopes.js
@@ -0,0 +1,224 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --expose-debug-as debug --harmony-block-scoping
+// The functions used for testing backtraces. They are at the top to make the
+// testing of source line/column easier.
+
+
+// Get the Debug object exposed from the debug context global object.
+Debug = debug.Debug;
+
+var test_name;
+var listener_delegate;
+var listener_called;
+var exception;
+var begin_test_count = 0;
+var end_test_count = 0;
+var break_count = 0;
+
+
+// Debug event listener which delegates.
+function listener(event, exec_state, event_data, data) {
+  try {
+    if (event == Debug.DebugEvent.Break) {
+      break_count++;
+      listener_called = true;
+      listener_delegate(exec_state);
+    }
+  } catch (e) {
+    exception = e;
+  }
+}
+
+// Add the debug event listener.
+Debug.setListener(listener);
+
+
+// Initialize for a new test.
+function BeginTest(name) {
+  test_name = name;
+  listener_delegate = null;
+  listener_called = false;
+  exception = null;
+  begin_test_count++;
+}
+
+
+// Check result of a test.
+function EndTest() {
+  assertTrue(listener_called, "listerner not called for " + test_name);
+  assertNull(exception, test_name);
+  end_test_count++;
+}
+
+
+// Check that the scope chain contains the expected types of scopes.
+function CheckScopeChain(scopes, exec_state) {
+  assertEquals(scopes.length, exec_state.frame().scopeCount());
+  for (var i = 0; i < scopes.length; i++) {
+    var scope = exec_state.frame().scope(i);
+    assertTrue(scope.isScope());
+    assertEquals(scopes[i], scope.scopeType());
+
+    // Check the global object when hitting the global scope.
+    if (scopes[i] == debug.ScopeType.Global) {
+      // Objects don't have same class (one is "global", other is "Object",
+      // so just check the properties directly.
+      assertPropertiesEqual(this, scope.scopeObject().value());
+    }
+  }
+
+  // Get the debug command processor.
+  var dcp = exec_state.debugCommandProcessor("unspecified_running_state");
+
+  // Send a scopes request and check the result.
+  var json;
+  var request_json = '{"seq":0,"type":"request","command":"scopes"}';
+  var response_json = dcp.processDebugJSONRequest(request_json);
+  var response = JSON.parse(response_json);
+  assertEquals(scopes.length, response.body.scopes.length);
+  for (var i = 0; i < scopes.length; i++) {
+    assertEquals(i, response.body.scopes[i].index);
+    assertEquals(scopes[i], response.body.scopes[i].type);
+    if (scopes[i] == debug.ScopeType.Local ||
+        scopes[i] == debug.ScopeType.Closure) {
+      assertTrue(response.body.scopes[i].object.ref < 0);
+    } else {
+      assertTrue(response.body.scopes[i].object.ref >= 0);
+    }
+    var found = false;
+    for (var j = 0; j < response.refs.length && !found; j++) {
+      found = response.refs[j].handle == response.body.scopes[i].object.ref;
+    }
+    assertTrue(found, "Scope object " + response.body.scopes[i].object.ref + " not found");
+  }
+}
+
+// Check that the content of the scope is as expected. For functions just check
+// that there is a function.
+function CheckScopeContent(content, number, exec_state) {
+  var scope = exec_state.frame().scope(number);
+  var count = 0;
+  for (var p in content) {
+    var property_mirror = scope.scopeObject().property(p);
+    if (property_mirror.isUndefined()) {
+      print('property ' + p + ' not found in scope');
+    }
+    assertFalse(property_mirror.isUndefined(), 'property ' + p + ' not found in scope');
+    if (typeof(content[p]) === 'function') {
+      assertTrue(property_mirror.value().isFunction());
+    } else {
+      assertEquals(content[p], property_mirror.value().value(), 'property ' + p + ' has unexpected value');
+    }
+    count++;
+  }
+
+  // 'arguments' and might be exposed in the local and closure scope. Just
+  // ignore this.
+  var scope_size = scope.scopeObject().properties().length;
+  if (!scope.scopeObject().property('arguments').isUndefined()) {
+    scope_size--;
+  }
+  // Also ignore synthetic variable from catch block.
+  if (!scope.scopeObject().property('.catch-var').isUndefined()) {
+    scope_size--;
+  }
+  // Skip property with empty name.
+  if (!scope.scopeObject().property('').isUndefined()) {
+    scope_size--;
+  }
+  // Also ignore synthetic variable from block scopes.
+  if (!scope.scopeObject().property('.block').isUndefined()) {
+    scope_size--;
+  }
+
+  if (count != scope_size) {
+    print('Names found in scope:');
+    var names = scope.scopeObject().propertyNames();
+    for (var i = 0; i < names.length; i++) {
+      print(names[i]);
+    }
+  }
+  assertEquals(count, scope_size);
+
+  // Get the debug command processor.
+  var dcp = exec_state.debugCommandProcessor("unspecified_running_state");
+
+  // Send a scope request for information on a single scope and check the
+  // result.
+  var request_json = '{"seq":0,"type":"request","command":"scope","arguments":{"number":';
+  request_json += scope.scopeIndex();
+  request_json += '}}';
+  var response_json = dcp.processDebugJSONRequest(request_json);
+  var response = JSON.parse(response_json);
+  assertEquals(scope.scopeType(), response.body.type);
+  assertEquals(number, response.body.index);
+  if (scope.scopeType() == debug.ScopeType.Local ||
+      scope.scopeType() == debug.ScopeType.Closure) {
+    assertTrue(response.body.object.ref < 0);
+  } else {
+    assertTrue(response.body.object.ref >= 0);
+  }
+  var found = false;
+  for (var i = 0; i < response.refs.length && !found; i++) {
+    found = response.refs[i].handle == response.body.object.ref;
+  }
+  assertTrue(found, "Scope object " + response.body.object.ref + " not found");
+}
+
+
+// Simple closure formed by returning an inner function referering to an outer
+// block local variable and an outer function's parameter. Due to VM
+// optimizations parts of the actual closure is missing from the debugger
+// information.
+BeginTest("Closure 1");
+
+function closure_1(a) {
+  var x = 2;
+  let y = 3;
+  if (true) {
+    let z = 4;
+    function f() {
+      debugger;
+      return a + x + y + z;
+    };
+    return f;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Local,
+                   debug.ScopeType.Block,
+                   debug.ScopeType.Closure,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({z:4}, 1, exec_state);
+  CheckScopeContent({a:1,x:2,y:3}, 2, exec_state);
+};
+closure_1(1)();
+EndTest();
diff --git a/test/mjsunit/d8-os.js b/test/mjsunit/d8-os.js
index 630a39e..fd6fb77 100644
--- a/test/mjsunit/d8-os.js
+++ b/test/mjsunit/d8-os.js
@@ -30,6 +30,9 @@
 // implemented on Windows, and even if it were then many of the things
 // we are calling would not be available.
 
+var TEST_DIR = "d8-os-test-directory-" + ((Math.random() * (1<<30)) | 0);
+
+
 function arg_error(str) {
   try {
     eval(str);
@@ -53,96 +56,98 @@
 if (this.os && os.system) {
   try {
     // Delete the dir if it is lying around from last time.
-    os.system("ls", ["d8-os-test-directory"]);
-    os.system("rm", ["-r", "d8-os-test-directory"]);
+    os.system("ls", [TEST_DIR]);
+    os.system("rm", ["-r", TEST_DIR]);
   } catch (e) {
   }
-  os.mkdirp("d8-os-test-directory");
-  os.chdir("d8-os-test-directory");
-  // Check the chdir worked.
-  os.system('ls', ['../d8-os-test-directory']);
-  // Simple create dir.
-  os.mkdirp("dir");
-  // Create dir in dir.
-  os.mkdirp("dir/foo");
-  // Check that they are there.
-  os.system('ls', ['dir/foo']);
-  // Check that we can detect when something is not there.
-  assertThrows("os.system('ls', ['dir/bar']);", "dir not there");
-  // Check that mkdirp makes intermediate directories.
-  os.mkdirp("dir2/foo");
-  os.system("ls", ["dir2/foo"]);
-  // Check that mkdirp doesn't mind if the dir is already there.
-  os.mkdirp("dir2/foo");
-  os.mkdirp("dir2/foo/");
-  // Check that mkdirp can cope with trailing /
-  os.mkdirp("dir3/");
-  os.system("ls", ["dir3"]);
-  // Check that we get an error if the name is taken by a file.
-  os.system("sh", ["-c", "echo foo > file1"]);
-  os.system("ls", ["file1"]);
-  assertThrows("os.mkdirp('file1');", "mkdir over file1");
-  assertThrows("os.mkdirp('file1/foo');", "mkdir over file2");
-  assertThrows("os.mkdirp('file1/');", "mkdir over file3");
-  assertThrows("os.mkdirp('file1/foo/');", "mkdir over file4");
-  // Create a dir we cannot read.
-  os.mkdirp("dir4", 0);
-  // This test fails if you are root since root can read any dir.
-  assertThrows("os.chdir('dir4');", "chdir dir4 I");
-  os.rmdir("dir4");
-  assertThrows("os.chdir('dir4');", "chdir dir4 II");
-  // Set umask.
-  var old_umask = os.umask(0777);
-  // Create a dir we cannot read.
-  os.mkdirp("dir5");
-  // This test fails if you are root since root can read any dir.
-  assertThrows("os.chdir('dir5');", "cd dir5 I");
-  os.rmdir("dir5");
-  assertThrows("os.chdir('dir5');", "chdir dir5 II");
-  os.umask(old_umask);
-
-  os.mkdirp("hest/fisk/../fisk/ged");
-  os.system("ls", ["hest/fisk/ged"]);
-
-  os.setenv("FOO", "bar");
-  var environment = os.system("printenv");
-  assertTrue(/FOO=bar/.test(environment));
-
-  // Check we time out.
-  var have_sleep = true;
-  var have_echo = true;
+  os.mkdirp(TEST_DIR);
+  os.chdir(TEST_DIR);
   try {
-    os.system("ls", ["/bin/sleep"]);
-  } catch (e) {
-    have_sleep = false;
-  }
-  try {
-    os.system("ls", ["/bin/echo"]);
-  } catch (e) {
-    have_echo = false;
-  }
-  if (have_sleep) {
-    assertThrows("os.system('sleep', ['2000'], 200);", "sleep 1");
+    // Check the chdir worked.
+    os.system('ls', ['../' + TEST_DIR]);
+    // Simple create dir.
+    os.mkdirp("dir");
+    // Create dir in dir.
+    os.mkdirp("dir/foo");
+    // Check that they are there.
+    os.system('ls', ['dir/foo']);
+    // Check that we can detect when something is not there.
+    assertThrows("os.system('ls', ['dir/bar']);", "dir not there");
+    // Check that mkdirp makes intermediate directories.
+    os.mkdirp("dir2/foo");
+    os.system("ls", ["dir2/foo"]);
+    // Check that mkdirp doesn't mind if the dir is already there.
+    os.mkdirp("dir2/foo");
+    os.mkdirp("dir2/foo/");
+    // Check that mkdirp can cope with trailing /
+    os.mkdirp("dir3/");
+    os.system("ls", ["dir3"]);
+    // Check that we get an error if the name is taken by a file.
+    os.system("sh", ["-c", "echo foo > file1"]);
+    os.system("ls", ["file1"]);
+    assertThrows("os.mkdirp('file1');", "mkdir over file1");
+    assertThrows("os.mkdirp('file1/foo');", "mkdir over file2");
+    assertThrows("os.mkdirp('file1/');", "mkdir over file3");
+    assertThrows("os.mkdirp('file1/foo/');", "mkdir over file4");
+    // Create a dir we cannot read.
+    os.mkdirp("dir4", 0);
+    // This test fails if you are root since root can read any dir.
+    assertThrows("os.chdir('dir4');", "chdir dir4 I");
+    os.rmdir("dir4");
+    assertThrows("os.chdir('dir4');", "chdir dir4 II");
+    // Set umask.
+    var old_umask = os.umask(0777);
+    // Create a dir we cannot read.
+    os.mkdirp("dir5");
+    // This test fails if you are root since root can read any dir.
+    assertThrows("os.chdir('dir5');", "cd dir5 I");
+    os.rmdir("dir5");
+    assertThrows("os.chdir('dir5');", "chdir dir5 II");
+    os.umask(old_umask);
 
-    // Check we time out with total time.
-    assertThrows("os.system('sleep', ['2000'], -1, 200);", "sleep 2");
+    os.mkdirp("hest/fisk/../fisk/ged");
+    os.system("ls", ["hest/fisk/ged"]);
 
-    // Check that -1 means no timeout.
-    os.system('sleep', ['1'], -1, -1);
+    os.setenv("FOO", "bar");
+    var environment = os.system("printenv");
+    assertTrue(/FOO=bar/.test(environment));
 
-  }
+    // Check we time out.
+    var have_sleep = true;
+    var have_echo = true;
+    try {
+      os.system("ls", ["/bin/sleep"]);
+    } catch (e) {
+      have_sleep = false;
+    }
+    try {
+      os.system("ls", ["/bin/echo"]);
+    } catch (e) {
+      have_echo = false;
+    }
+    if (have_sleep) {
+      assertThrows("os.system('sleep', ['2000'], 200);", "sleep 1");
 
-  // Check that we don't fill up the process table with zombies.
-  // Disabled because it's too slow.
-  if (have_echo) {
-    //for (var i = 0; i < 65536; i++) {
+      // Check we time out with total time.
+      assertThrows("os.system('sleep', ['2000'], -1, 200);", "sleep 2");
+
+      // Check that -1 means no timeout.
+      os.system('sleep', ['1'], -1, -1);
+
+    }
+
+    // Check that we don't fill up the process table with zombies.
+    // Disabled because it's too slow.
+    if (have_echo) {
+      //for (var i = 0; i < 65536; i++) {
       assertEquals("baz\n", os.system("echo", ["baz"]));
-    //}
+      //}
+    }
+  } finally {
+    os.chdir("..");
+    os.system("rm", ["-r", TEST_DIR]);
   }
 
-  os.chdir("..");
-  os.system("rm", ["-r", "d8-os-test-directory"]);
-
   // Too few args.
   arg_error("os.umask();");
   arg_error("os.system();");
diff --git a/test/mjsunit/debug-script.js b/test/mjsunit/debug-script.js
index 643dd8c..9767888 100644
--- a/test/mjsunit/debug-script.js
+++ b/test/mjsunit/debug-script.js
@@ -34,13 +34,19 @@
 
 // Count script types.
 var named_native_count = 0;
+var named_native_names = {};
 var extension_count = 0;
 var normal_count = 0;
 var scripts = Debug.scripts();
 for (i = 0; i < scripts.length; i++) {
   if (scripts[i].type == Debug.ScriptType.Native) {
     if (scripts[i].name) {
-      named_native_count++;
+      // TODO(1641): Remove check for equally named native scripts once the
+      // underlying issue is fixed.
+      if (!named_native_names[scripts[i].name]) {
+        named_native_names[scripts[i].name] = true;
+        named_native_count++;
+      }
     }
   } else if (scripts[i].type == Debug.ScriptType.Extension) {
     extension_count++;
diff --git a/test/mjsunit/external-array.js b/test/mjsunit/external-array.js
index 94105ec..d7e9de0 100644
--- a/test/mjsunit/external-array.js
+++ b/test/mjsunit/external-array.js
@@ -190,9 +190,19 @@
   gc();  // Makes V8 forget about type information for test_func.
 }
 
+function run_bounds_test(test_func, array, expected_result) {
+  assertEquals(undefined, a[kElementCount]);
+  a[kElementCount] = 456;
+  assertEquals(undefined, a[kElementCount]);
+  assertEquals(undefined, a[kElementCount+1]);
+  a[kElementCount+1] = 456;
+  assertEquals(undefined, a[kElementCount+1]);
+}
+
 for (var t = 0; t < types.length; t++) {
   var type = types[t];
   var a = new type(kElementCount);
+
   for (var i = 0; i < kElementCount; i++) {
     a[i] = i;
   }
@@ -220,6 +230,16 @@
     assertTrue(delete a.length);
     a.length = 2;
     assertEquals(2, a.length);
+
+    // Make sure bounds checks are handled correctly for external arrays.
+    run_bounds_test(a);
+    run_bounds_test(a);
+    run_bounds_test(a);
+    %OptimizeFunctionOnNextCall(run_bounds_test);
+    run_bounds_test(a);
+    %DeoptimizeFunction(run_bounds_test);
+    gc();  // Makes V8 forget about type information for test_func.
+
   }
 
   function array_load_set_smi_check(a) {
diff --git a/test/mjsunit/fuzz-natives.js b/test/mjsunit/fuzz-natives.js
index ffa9268..f8f0a28 100644
--- a/test/mjsunit/fuzz-natives.js
+++ b/test/mjsunit/fuzz-natives.js
@@ -146,6 +146,7 @@
   "NewStrictArgumentsFast": true,
   "PushWithContext": true,
   "PushCatchContext": true,
+  "PushBlockContext": true,
   "LazyCompile": true,
   "LazyRecompile": true,
   "NotifyDeoptimized": true,
diff --git a/src/shell.h b/test/mjsunit/harmony/block-lazy-compile.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/harmony/block-lazy-compile.js
index ca51040..a6efcbf 100644
--- a/src/shell.h
+++ b/test/mjsunit/harmony/block-lazy-compile.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,27 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --allow-natives-syntax
+// Test deserialization of block contexts during lazy compilation
+// of closures.
 
-#include "../public/debug.h"
+function f() {
+  var g;
+  {
+    // TODO(keuchel): introduce let
+    var x = 0;
+    g = function () {
+      x = x + 1;
+      return x;
+    }
+  }
+  return g;
+}
 
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+var o = f();
+assertEquals(1, o());
+assertEquals(2, o());
+assertEquals(3, o());
+%OptimizeFunctionOnNextCall(o);
+assertEquals(4, o());
diff --git a/src/shell.h b/test/mjsunit/harmony/block-let-crankshaft.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/harmony/block-let-crankshaft.js
index ca51040..c2fb96b 100644
--- a/src/shell.h
+++ b/test/mjsunit/harmony/block-let-crankshaft.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,40 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --harmony-block-scoping --allow-natives-syntax
 
-#include "../public/debug.h"
+// Test that temporal dead zone semantics for function and block scoped
+// ket bindings are handled by the optimizing compiler.
 
-namespace v8 {
-namespace internal {
+function f(x, b) {
+  let y = (b ? y : x) + 42;
+  return y;
+}
 
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
+function g(x, b) {
+  {
+    let y = (b ? y : x) + 42;
+    return y;
+  }
+}
 
+for (var i=0; i<10; i++) {
+  f(i, false);
+  g(i, false);
+}
 
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
+%OptimizeFunctionOnNextCall(f);
+%OptimizeFunctionOnNextCall(g);
 
-} }  // namespace v8::internal
+try {
+  f(42, true);
+} catch (e) {
+  assertInstanceof(e, ReferenceError);
+}
 
-#endif  // V8_SHELL_H_
+try {
+  g(42, true);
+} catch (e) {
+  assertInstanceof(e, ReferenceError);
+}
diff --git a/src/shell.h b/test/mjsunit/harmony/block-let-declaration.js
similarity index 61%
copy from src/shell.h
copy to test/mjsunit/harmony/block-let-declaration.js
index ca51040..19c943f 100644
--- a/src/shell.h
+++ b/test/mjsunit/harmony/block-let-declaration.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,44 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --harmony-block-scoping
 
-#include "../public/debug.h"
+// Test let declarations in various settings.
 
-namespace v8 {
-namespace internal {
+// Global
+let x;
+let y = 2;
 
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
+// Block local
+{
+  let y;
+  let x = 3;
+}
 
+assertEquals(undefined, x);
+assertEquals(2,y);
 
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
+if (true) {
+  let y;
+  assertEquals(undefined, y);
+}
 
-} }  // namespace v8::internal
+function TestLocalThrows(str, expect) {
+  assertThrows("(function(){" + str + "})()", expect);
+}
 
-#endif  // V8_SHELL_H_
+function TestLocalDoesNotThrow(str) {
+  assertDoesNotThrow("(function(){" + str + "})()");
+}
+
+// Unprotected statement
+TestLocalThrows("if (true) let x;", SyntaxError);
+TestLocalThrows("with ({}) let x;", SyntaxError);
+TestLocalThrows("do let x; while (false)", SyntaxError);
+TestLocalThrows("while (false) let x;", SyntaxError);
+
+TestLocalDoesNotThrow("if (true) var x;");
+TestLocalDoesNotThrow("with ({}) var x;");
+TestLocalDoesNotThrow("do var x; while (false)");
+TestLocalDoesNotThrow("while (false) var x;");
diff --git a/test/mjsunit/harmony/block-let-semantics.js b/test/mjsunit/harmony/block-let-semantics.js
new file mode 100644
index 0000000..198c3b4
--- /dev/null
+++ b/test/mjsunit/harmony/block-let-semantics.js
@@ -0,0 +1,138 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --harmony-block-scoping
+
+// Test temporal dead zone semantics of let bound variables in
+// function and block scopes.
+
+function TestFunctionLocal(s) {
+  try {
+    eval("(function(){" + s + "; })")();
+  } catch (e) {
+    assertInstanceof(e, ReferenceError);
+    return;
+  }
+  assertUnreachable();
+}
+
+function TestBlockLocal(s,e) {
+  try {
+    eval("(function(){ {" + s + ";} })")();
+  } catch (e) {
+    assertInstanceof(e, ReferenceError);
+    return;
+  }
+  assertUnreachable();
+}
+
+
+function TestAll(s) {
+  TestBlockLocal(s);
+  TestFunctionLocal(s);
+}
+
+// Use before initialization in declaration statement.
+TestAll('let x = x + 1');
+TestAll('let x = x += 1');
+TestAll('let x = x++');
+TestAll('let x = ++x');
+
+// Use before initialization in prior statement.
+TestAll('x + 1; let x;');
+TestAll('x = 1; let x;');
+TestAll('x += 1; let x;');
+TestAll('++x; let x;');
+TestAll('x++; let x;');
+
+TestAll('f(); let x; function f() { return x + 1; }');
+TestAll('f(); let x; function f() { x = 1; }');
+TestAll('f(); let x; function f() { x += 1; }');
+TestAll('f(); let x; function f() { ++x; }');
+TestAll('f(); let x; function f() { x++; }');
+
+TestAll('f()(); let x; function f() { return function() { return x + 1; } }');
+TestAll('f()(); let x; function f() { return function() { x = 1; } }');
+TestAll('f()(); let x; function f() { return function() { x += 1; } }');
+TestAll('f()(); let x; function f() { return function() { ++x; } }');
+TestAll('f()(); let x; function f() { return function() { x++; } }');
+
+// Use in before initialization with a dynamic lookup.
+TestAll('eval("x + 1;"); let x;');
+TestAll('eval("x = 1;"); let x;');
+TestAll('eval("x += 1;"); let x;');
+TestAll('eval("++x;"); let x;');
+TestAll('eval("x++;"); let x;');
+
+// Test that variables introduced by function declarations are created and
+// initialized upon entering a function / block scope.
+function f() {
+  {
+    assertEquals(2, g1());
+    assertEquals(2, eval("g1()"));
+
+    // block scoped function declaration
+    function g1() {
+      return 2;
+    }
+  }
+
+  assertEquals(3, g2());
+  assertEquals(3, eval("g2()"));
+  // function scoped function declaration
+  function g2() {
+    return 3;
+  }
+}
+f();
+
+// Test that a function declaration introduces a block scoped variable.
+TestAll('{ function k() { return 0; } }; k(); ');
+
+// Test that a function declaration sees the scope it resides in.
+function f2() {
+  let m, n;
+  {
+    m = g;
+    function g() {
+      return a;
+    }
+    let a = 1;
+  }
+  assertEquals(1, m());
+
+  try {
+    throw 2;
+  } catch(b) {
+    n = h;
+    function h() {
+      return b + c;
+    }
+    let b = 3;
+  }
+  assertEquals(5, n());
+}
diff --git a/test/mjsunit/harmony/block-scoping.js b/test/mjsunit/harmony/block-scoping.js
new file mode 100644
index 0000000..266e380
--- /dev/null
+++ b/test/mjsunit/harmony/block-scoping.js
@@ -0,0 +1,216 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax --harmony-block-scoping
+// Test functionality of block scopes.
+
+// Hoisting of var declarations.
+function f1() {
+  {
+    var x = 1;
+    var y;
+  }
+  assertEquals(1, x)
+  assertEquals(undefined, y)
+}
+f1();
+
+
+// Dynamic lookup in and through block contexts.
+function f2(one) {
+  var x = one + 1;
+  let y = one + 2;
+  {
+    let z = one + 3;
+    assertEquals(1, eval('one'));
+    assertEquals(2, eval('x'));
+    assertEquals(3, eval('y'));
+    assertEquals(4, eval('z'));
+  }
+}
+f2(1);
+
+
+// Lookup in and through block contexts.
+function f3(one) {
+  var x = one + 1;
+  let y = one + 2;
+  {
+    let z = one + 3;
+    assertEquals(1, one);
+    assertEquals(2, x);
+    assertEquals(3, y);
+    assertEquals(4, z);
+  }
+}
+f3(1);
+
+
+// Dynamic lookup from closure.
+function f4(one) {
+  var x = one + 1;
+  let y = one + 2;
+  {
+    let z = one + 3;
+    function f() {
+      assertEquals(1, eval('one'));
+      assertEquals(2, eval('x'));
+      assertEquals(3, eval('y'));
+      assertEquals(4, eval('z'));
+    };
+  }
+}
+f4(1);
+
+
+// Lookup from closure.
+function f5(one) {
+  var x = one + 1;
+  let y = one + 2;
+  {
+    let z = one + 3;
+    function f() {
+      assertEquals(1, one);
+      assertEquals(2, x);
+      assertEquals(3, y);
+      assertEquals(4, z);
+    };
+  }
+}
+f5(1);
+
+
+// Return from block.
+function f6() {
+  let x = 1;
+  {
+    let y = 2;
+    return x + y;
+  }
+}
+assertEquals(3, f6(6));
+
+
+// Variable shadowing and lookup.
+function f7(a) {
+  let b = 1;
+  var c = 1;
+  var d = 1;
+  { // let variables shadowing argument, let and var variables
+    let a = 2;
+    let b = 2;
+    let c = 2;
+    assertEquals(2,a);
+    assertEquals(2,b);
+    assertEquals(2,c);
+  }
+  try {
+    throw 'stuff1';
+  } catch (a) {
+    assertEquals('stuff1',a);
+    // catch variable shadowing argument
+    a = 2;
+    assertEquals(2,a);
+    {
+      // let variable shadowing catch variable
+      let a = 3;
+      assertEquals(3,a);
+      try {
+        throw 'stuff2';
+      } catch (a) {
+        assertEquals('stuff2',a);
+        // catch variable shadowing let variable
+        a = 4;
+        assertEquals(4,a);
+      }
+      assertEquals(3,a);
+    }
+    assertEquals(2,a);
+  }
+  try {
+    throw 'stuff3';
+  } catch (c) {
+    // catch variable shadowing var variable
+    assertEquals('stuff3',c);
+    try {
+      throw 'stuff4';
+    } catch(c) {
+      assertEquals('stuff4',c);
+      // catch variable shadowing catch variable
+      c = 3;
+      assertEquals(3,c);
+    }
+    (function(c) {
+      // argument shadowing catch variable
+      c = 3;
+      assertEquals(3,c);
+    })();
+    assertEquals('stuff3', c);
+    (function() {
+      // var variable shadowing catch variable
+      var c = 3;
+    })();
+    assertEquals('stuff3', c);
+    c = 2;
+  }
+  assertEquals(1,c);
+  (function(a,b,c) {
+    // arguments shadowing argument, let and var variable
+    a = 2;
+    b = 2;
+    c = 2;
+    assertEquals(2,a);
+    assertEquals(2,b);
+    assertEquals(2,c);
+    // var variable shadowing var variable
+    var d = 2;
+  })(1,1);
+  assertEquals(1,a);
+  assertEquals(1,b);
+  assertEquals(1,c);
+  assertEquals(1,d);
+}
+f7(1);
+
+
+// Ensure let variables are block local and var variables function local.
+function f8() {
+  var let_accessors = [];
+  var var_accessors = [];
+  for (var i = 0; i < 10; i++) {
+    let x = i;
+    var y = i;
+    let_accessors[i] = function() { return x; }
+    var_accessors[i] = function() { return y; }
+  }
+  for (var j = 0; j < 10; j++) {
+    y = j + 10;
+    assertEquals(j, let_accessors[j]());
+    assertEquals(y, var_accessors[j]());
+  }
+}
+f8();
diff --git a/test/mjsunit/harmony/debug-blockscopes.js b/test/mjsunit/harmony/debug-blockscopes.js
new file mode 100644
index 0000000..e0df71b
--- /dev/null
+++ b/test/mjsunit/harmony/debug-blockscopes.js
@@ -0,0 +1,389 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --expose-debug-as debug --harmony-block-scoping
+// The functions used for testing backtraces. They are at the top to make the
+// testing of source line/column easier.
+
+
+// Get the Debug object exposed from the debug context global object.
+Debug = debug.Debug;
+
+var test_name;
+var listener_delegate;
+var listener_called;
+var exception;
+var begin_test_count = 0;
+var end_test_count = 0;
+var break_count = 0;
+
+
+// Debug event listener which delegates.
+function listener(event, exec_state, event_data, data) {
+  try {
+    if (event == Debug.DebugEvent.Break) {
+      break_count++;
+      listener_called = true;
+      listener_delegate(exec_state);
+    }
+  } catch (e) {
+    exception = e;
+  }
+}
+
+// Add the debug event listener.
+Debug.setListener(listener);
+
+
+// Initialize for a new test.
+function BeginTest(name) {
+  test_name = name;
+  listener_delegate = null;
+  listener_called = false;
+  exception = null;
+  begin_test_count++;
+}
+
+
+// Check result of a test.
+function EndTest() {
+  assertTrue(listener_called, "listerner not called for " + test_name);
+  assertNull(exception, test_name);
+  end_test_count++;
+}
+
+
+// Check that the scope chain contains the expected types of scopes.
+function CheckScopeChain(scopes, exec_state) {
+  assertEquals(scopes.length, exec_state.frame().scopeCount());
+  for (var i = 0; i < scopes.length; i++) {
+    var scope = exec_state.frame().scope(i);
+    assertTrue(scope.isScope());
+    assertEquals(scopes[i], scope.scopeType());
+
+    // Check the global object when hitting the global scope.
+    if (scopes[i] == debug.ScopeType.Global) {
+      // Objects don't have same class (one is "global", other is "Object",
+      // so just check the properties directly.
+      assertPropertiesEqual(this, scope.scopeObject().value());
+    }
+  }
+
+  // Get the debug command processor.
+  var dcp = exec_state.debugCommandProcessor("unspecified_running_state");
+
+  // Send a scopes request and check the result.
+  var json;
+  var request_json = '{"seq":0,"type":"request","command":"scopes"}';
+  var response_json = dcp.processDebugJSONRequest(request_json);
+  var response = JSON.parse(response_json);
+  assertEquals(scopes.length, response.body.scopes.length);
+  for (var i = 0; i < scopes.length; i++) {
+    assertEquals(i, response.body.scopes[i].index);
+    assertEquals(scopes[i], response.body.scopes[i].type);
+    if (scopes[i] == debug.ScopeType.Local ||
+        scopes[i] == debug.ScopeType.Closure) {
+      assertTrue(response.body.scopes[i].object.ref < 0);
+    } else {
+      assertTrue(response.body.scopes[i].object.ref >= 0);
+    }
+    var found = false;
+    for (var j = 0; j < response.refs.length && !found; j++) {
+      found = response.refs[j].handle == response.body.scopes[i].object.ref;
+    }
+    assertTrue(found, "Scope object " + response.body.scopes[i].object.ref + " not found");
+  }
+}
+
+// Check that the content of the scope is as expected. For functions just check
+// that there is a function.
+function CheckScopeContent(content, number, exec_state) {
+  var scope = exec_state.frame().scope(number);
+  var count = 0;
+  for (var p in content) {
+    var property_mirror = scope.scopeObject().property(p);
+    if (property_mirror.isUndefined()) {
+      print('property ' + p + ' not found in scope');
+    }
+    assertFalse(property_mirror.isUndefined(), 'property ' + p + ' not found in scope');
+    if (typeof(content[p]) === 'function') {
+      assertTrue(property_mirror.value().isFunction());
+    } else {
+      assertEquals(content[p], property_mirror.value().value(), 'property ' + p + ' has unexpected value');
+    }
+    count++;
+  }
+
+  // 'arguments' and might be exposed in the local and closure scope. Just
+  // ignore this.
+  var scope_size = scope.scopeObject().properties().length;
+  if (!scope.scopeObject().property('arguments').isUndefined()) {
+    scope_size--;
+  }
+  // Also ignore synthetic variable from catch block.
+  if (!scope.scopeObject().property('.catch-var').isUndefined()) {
+    scope_size--;
+  }
+  // Skip property with empty name.
+  if (!scope.scopeObject().property('').isUndefined()) {
+    scope_size--;
+  }
+  // Also ignore synthetic variable from block scopes.
+  if (!scope.scopeObject().property('.block').isUndefined()) {
+    scope_size--;
+  }
+
+  if (count != scope_size) {
+    print('Names found in scope:');
+    var names = scope.scopeObject().propertyNames();
+    for (var i = 0; i < names.length; i++) {
+      print(names[i]);
+    }
+  }
+  assertEquals(count, scope_size);
+
+  // Get the debug command processor.
+  var dcp = exec_state.debugCommandProcessor("unspecified_running_state");
+
+  // Send a scope request for information on a single scope and check the
+  // result.
+  var request_json = '{"seq":0,"type":"request","command":"scope","arguments":{"number":';
+  request_json += scope.scopeIndex();
+  request_json += '}}';
+  var response_json = dcp.processDebugJSONRequest(request_json);
+  var response = JSON.parse(response_json);
+  assertEquals(scope.scopeType(), response.body.type);
+  assertEquals(number, response.body.index);
+  if (scope.scopeType() == debug.ScopeType.Local ||
+      scope.scopeType() == debug.ScopeType.Closure) {
+    assertTrue(response.body.object.ref < 0);
+  } else {
+    assertTrue(response.body.object.ref >= 0);
+  }
+  var found = false;
+  for (var i = 0; i < response.refs.length && !found; i++) {
+    found = response.refs[i].handle == response.body.object.ref;
+  }
+  assertTrue(found, "Scope object " + response.body.object.ref + " not found");
+}
+
+
+// Simple empty block scope in local scope.
+BeginTest("Local block 1");
+
+function local_block_1() {
+  {
+    debugger;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({}, 1, exec_state);
+};
+local_block_1();
+EndTest();
+
+
+// Local scope with a parameter.
+BeginTest("Local 2");
+
+function local_2(a) {
+  {
+    debugger;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({a:1}, 1, exec_state);
+};
+local_2(1);
+EndTest();
+
+
+// Local scope with a parameter and a local variable.
+BeginTest("Local 3");
+
+function local_3(a) {
+  let x = 3;
+  debugger;
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({a:1,x:3}, 0, exec_state);
+};
+local_3(1);
+EndTest();
+
+
+// Local scope with parameters and local variables.
+BeginTest("Local 4");
+
+function local_4(a, b) {
+  let x = 3;
+  let y = 4;
+  debugger;
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({a:1,b:2,x:3,y:4}, 0, exec_state);
+};
+local_4(1, 2);
+EndTest();
+
+
+// Single empty with block.
+BeginTest("With block 1");
+
+function with_block_1() {
+  with({}) {
+    debugger;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.With,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({}, 1, exec_state);
+};
+with_block_1();
+EndTest();
+
+
+// Nested empty with blocks.
+BeginTest("With block 2");
+
+function with_block_2() {
+  with({}) {
+    with({}) {
+      debugger;
+    }
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.With,
+                   debug.ScopeType.Block,
+                   debug.ScopeType.With,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({}, 1, exec_state);
+  CheckScopeContent({}, 2, exec_state);
+  CheckScopeContent({}, 3, exec_state);
+};
+with_block_2();
+EndTest();
+
+
+// With block using an in-place object literal.
+BeginTest("With block 3");
+
+function with_block_3() {
+  with({a:1,b:2}) {
+    debugger;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.With,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({a:1,b:2}, 1, exec_state);
+};
+with_block_3();
+EndTest();
+
+
+// Nested with blocks using in-place object literals.
+BeginTest("With block 4");
+
+function with_block_4() {
+  with({a:1,b:2}) {
+    with({a:2,b:1}) {
+      debugger;
+    }
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.With,
+                   debug.ScopeType.Block,
+                   debug.ScopeType.With,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({a:2,b:1}, 1, exec_state);
+  CheckScopeContent({a:1,b:2}, 3, exec_state);
+};
+with_block_4();
+EndTest();
+
+
+// Simple closure formed by returning an inner function referering to an outer
+// block local variable and an outer function's parameter.
+BeginTest("Closure 1");
+
+function closure_1(a) {
+  var x = 2;
+  let y = 3;
+  if (true) {
+    let z = 4;
+    function f() {
+      debugger;
+      return a + x + y + z;
+    };
+    return f;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Local,
+                   debug.ScopeType.Block,
+                   debug.ScopeType.Closure,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({a:1,x:2,y:3}, 2, exec_state);
+};
+closure_1(1)();
+EndTest();
diff --git a/src/shell.h b/test/mjsunit/harmony/debug-evaluate-blockscopes.js
similarity index 60%
copy from src/shell.h
copy to test/mjsunit/harmony/debug-evaluate-blockscopes.js
index ca51040..549960a 100644
--- a/src/shell.h
+++ b/test/mjsunit/harmony/debug-evaluate-blockscopes.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,41 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --expose-debug-as debug --harmony-block-scoping
 
-#include "../public/debug.h"
+// Test debug evaluation for functions without local context, but with
+// nested catch contexts.
 
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
+function f() {
+  {                   // Line 1.
+    let i = 1;        // Line 2.
+    try {             // Line 3.
+      throw 'stuff';  // Line 4.
+    } catch (e) {     // Line 5.
+      x = 2;          // Line 6.
+    }
+  }
 };
 
-} }  // namespace v8::internal
+// Get the Debug object exposed from the debug context global object.
+Debug = debug.Debug
+// Set breakpoint on line 6.
+var bp = Debug.setBreakPoint(f, 6);
 
-#endif  // V8_SHELL_H_
+function listener(event, exec_state, event_data, data) {
+  if (event == Debug.DebugEvent.Break) {
+    result = exec_state.frame().evaluate("i").value();
+  }
+};
+
+// Add the debug event listener.
+Debug.setListener(listener);
+result = -1;
+f();
+assertEquals(1, result);
+
+// Clear breakpoint.
+Debug.clearBreakPoint(bp);
+// Get rid of the debug event listener.
+Debug.setListener(null);
diff --git a/test/mjsunit/harmony/proxies.js b/test/mjsunit/harmony/proxies.js
index 84641d5..640033d 100644
--- a/test/mjsunit/harmony/proxies.js
+++ b/test/mjsunit/harmony/proxies.js
@@ -42,22 +42,27 @@
 TestGet({
   get: function(r, k) { return 42 }
 })
+
 TestGet({
   get: function(r, k) { return this.get2(r, k) },
   get2: function(r, k) { return 42 }
 })
+
 TestGet({
   getPropertyDescriptor: function(k) { return {value: 42} }
 })
+
 TestGet({
   getPropertyDescriptor: function(k) { return this.getPropertyDescriptor2(k) },
   getPropertyDescriptor2: function(k) { return {value: 42} }
 })
+
 TestGet({
   getPropertyDescriptor: function(k) {
     return {get value() { return 42 }}
   }
 })
+
 TestGet({
   get: undefined,
   getPropertyDescriptor: function(k) { return {value: 42} }
@@ -83,32 +88,38 @@
 TestGetCall({
   get: function(r, k) { return function() { return 55 } }
 })
+
 TestGetCall({
   get: function(r, k) { return this.get2(r, k) },
   get2: function(r, k) { return function() { return 55 } }
 })
+
 TestGetCall({
   getPropertyDescriptor: function(k) {
     return {value: function() { return 55 }}
   }
 })
+
 TestGetCall({
   getPropertyDescriptor: function(k) { return this.getPropertyDescriptor2(k) },
   getPropertyDescriptor2: function(k) {
     return {value: function() { return 55 }}
   }
 })
+
 TestGetCall({
   getPropertyDescriptor: function(k) {
     return {get value() { return function() { return 55 } }}
   }
 })
+
 TestGetCall({
   get: undefined,
   getPropertyDescriptor: function(k) {
     return {value: function() { return 55 }}
   }
 })
+
 TestGetCall({
   get: function(r, k) {
     if (k == "gg") {
@@ -146,14 +157,17 @@
 TestSet({
   set: function(r, k, v) { key = k; val = v; return true }
 })
+
 TestSet({
   set: function(r, k, v) { return this.set2(r, k, v) },
   set2: function(r, k, v) { key = k; val = v; return true }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) { return {writable: true} },
   defineProperty: function(k, desc) { key = k; val = desc.value }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) {
     return this.getOwnPropertyDescriptor2(k)
@@ -162,22 +176,26 @@
   defineProperty: function(k, desc) { this.defineProperty2(k, desc) },
   defineProperty2: function(k, desc) { key = k; val = desc.value }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) {
     return {get writable() { return true }}
   },
   defineProperty: function(k, desc) { key = k; val = desc.value }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) {
     return {set: function(v) { key = k; val = v }}
   }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) { return null },
   getPropertyDescriptor: function(k) { return {writable: true} },
   defineProperty: function(k, desc) { key = k; val = desc.value }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) { return null },
   getPropertyDescriptor: function(k) {
@@ -185,12 +203,14 @@
   },
   defineProperty: function(k, desc) { key = k; val = desc.value }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) { return null },
   getPropertyDescriptor: function(k) {
     return {set: function(v) { key = k; val = v }}
   }
 })
+
 TestSet({
   getOwnPropertyDescriptor: function(k) { return null },
   getPropertyDescriptor: function(k) { return null },
@@ -279,10 +299,12 @@
 TestDefine({
   defineProperty: function(k, d) { key = k; desc = d; return true }
 })
+
 TestDefine({
   defineProperty: function(k, d) { return this.defineProperty2(k, d) },
   defineProperty2: function(k, d) { key = k; desc = d; return true }
 })
+
 TestDefine(Proxy.create({
   get: function(pr, pk) {
     return function(k, d) { key = k; desc = d; return true }
@@ -323,10 +345,12 @@
 TestDelete({
   'delete': function(k) { key = k; return k < "z" }
 })
+
 TestDelete({
   'delete': function(k) { return this.delete2(k) },
   delete2: function(k) { key = k; return k < "z" }
 })
+
 TestDelete(Proxy.create({
   get: function(pr, pk) {
     return function(k) { key = k; return k < "z" }
@@ -363,6 +387,7 @@
   defineProperty: function(k, d) { this["__" + k] = d; return true },
   getOwnPropertyDescriptor: function(k) { return this["__" + k] }
 })
+
 TestDescriptor({
   defineProperty: function(k, d) { this["__" + k] = d; return true },
   getOwnPropertyDescriptor: function(k) {
@@ -404,7 +429,7 @@
 
 
 
-// Element (in).
+// Membership test (in).
 
 var key
 function TestIn(handler) {
@@ -442,26 +467,31 @@
 TestIn({
   has: function(k) { key = k; return k < "z" }
 })
+
 TestIn({
   has: function(k) { return this.has2(k) },
   has2: function(k) { key = k; return k < "z" }
 })
+
 TestIn({
   getPropertyDescriptor: function(k) {
     key = k; return k < "z" ? {value: 42} : void 0
   }
 })
+
 TestIn({
   getPropertyDescriptor: function(k) { return this.getPropertyDescriptor2(k) },
   getPropertyDescriptor2: function(k) {
     key = k; return k < "z" ? {value: 42} : void 0
   }
 })
+
 TestIn({
   getPropertyDescriptor: function(k) {
     key = k; return k < "z" ? {get value() { return 42 }} : void 0
   }
 })
+
 TestIn({
   get: undefined,
   getPropertyDescriptor: function(k) {
@@ -477,7 +507,65 @@
 
 
 
-// Instanceof (instanceof).
+// Own Properties (Object.prototype.hasOwnProperty).
+
+var key
+function TestHasOwn(handler) {
+  var o = Proxy.create(handler)
+  assertTrue(Object.prototype.hasOwnProperty.call(o, "a"))
+  assertEquals("a", key)
+  assertTrue(Object.prototype.hasOwnProperty.call(o, 99))
+  assertEquals("99", key)
+  assertFalse(Object.prototype.hasOwnProperty.call(o, "z"))
+  assertEquals("z", key)
+}
+
+TestHasOwn({
+  hasOwn: function(k) { key = k; return k < "z" }
+})
+
+TestHasOwn({
+  hasOwn: function(k) { return this.hasOwn2(k) },
+  hasOwn2: function(k) { key = k; return k < "z" }
+})
+
+TestHasOwn({
+  getOwnPropertyDescriptor: function(k) {
+    key = k; return k < "z" ? {value: 42} : void 0
+  }
+})
+
+TestHasOwn({
+  getOwnPropertyDescriptor: function(k) {
+    return this.getOwnPropertyDescriptor2(k)
+  },
+  getOwnPropertyDescriptor2: function(k) {
+    key = k; return k < "z" ? {value: 42} : void 0
+  }
+})
+
+TestHasOwn({
+  getOwnPropertyDescriptor: function(k) {
+    key = k; return k < "z" ? {get value() { return 42 }} : void 0
+  }
+})
+
+TestHasOwn({
+  hasOwn: undefined,
+  getOwnPropertyDescriptor: function(k) {
+    key = k; return k < "z" ? {value: 42} : void 0
+  }
+})
+
+TestHasOwn(Proxy.create({
+  get: function(pr, pk) {
+    return function(k) { key = k; return k < "z" }
+  }
+}))
+
+
+
+// Instanceof (instanceof)
 
 function TestInstanceof() {
   var o = {}
@@ -514,7 +602,7 @@
 
 
 
-// Prototype (Object.getPrototypeOf).
+// Prototype (Object.getPrototypeOf, Object.prototype.isPrototypeOf).
 
 function TestPrototype() {
   var o = {}
@@ -528,6 +616,32 @@
   assertSame(Object.getPrototypeOf(p2), o)
   assertSame(Object.getPrototypeOf(p3), p2)
   assertSame(Object.getPrototypeOf(p4), null)
+
+  assertTrue(Object.prototype.isPrototypeOf(o))
+  assertFalse(Object.prototype.isPrototypeOf(p1))
+  assertTrue(Object.prototype.isPrototypeOf(p2))
+  assertTrue(Object.prototype.isPrototypeOf(p3))
+  assertFalse(Object.prototype.isPrototypeOf(p4))
+  assertTrue(Object.prototype.isPrototypeOf.call(Object.prototype, o))
+  assertFalse(Object.prototype.isPrototypeOf.call(Object.prototype, p1))
+  assertTrue(Object.prototype.isPrototypeOf.call(Object.prototype, p2))
+  assertTrue(Object.prototype.isPrototypeOf.call(Object.prototype, p3))
+  assertFalse(Object.prototype.isPrototypeOf.call(Object.prototype, p4))
+  assertFalse(Object.prototype.isPrototypeOf.call(o, o))
+  assertFalse(Object.prototype.isPrototypeOf.call(o, p1))
+  assertTrue(Object.prototype.isPrototypeOf.call(o, p2))
+  assertTrue(Object.prototype.isPrototypeOf.call(o, p3))
+  assertFalse(Object.prototype.isPrototypeOf.call(o, p4))
+  assertFalse(Object.prototype.isPrototypeOf.call(p1, p1))
+  assertFalse(Object.prototype.isPrototypeOf.call(p1, o))
+  assertFalse(Object.prototype.isPrototypeOf.call(p1, p2))
+  assertFalse(Object.prototype.isPrototypeOf.call(p1, p3))
+  assertFalse(Object.prototype.isPrototypeOf.call(p1, p4))
+  assertFalse(Object.prototype.isPrototypeOf.call(p2, p1))
+  assertFalse(Object.prototype.isPrototypeOf.call(p2, p2))
+  assertTrue(Object.prototype.isPrototypeOf.call(p2, p3))
+  assertFalse(Object.prototype.isPrototypeOf.call(p2, p4))
+  assertFalse(Object.prototype.isPrototypeOf.call(p3, p2))
 }
 
 TestPrototype()
@@ -544,13 +658,16 @@
 TestPropertyNames([], {
   getOwnPropertyNames: function() { return [] }
 })
+
 TestPropertyNames(["a", "zz", " ", "0"], {
   getOwnPropertyNames: function() { return ["a", "zz", " ", 0] }
 })
+
 TestPropertyNames(["throw", "function "], {
   getOwnPropertyNames: function() { return this.getOwnPropertyNames2() },
   getOwnPropertyNames2: function() { return ["throw", "function "] }
 })
+
 TestPropertyNames(["[object Object]"], {
   get getOwnPropertyNames() {
     return function() { return [{}] }
@@ -566,22 +683,27 @@
 TestKeys([], {
   keys: function() { return [] }
 })
+
 TestKeys(["a", "zz", " ", "0"], {
   keys: function() { return ["a", "zz", " ", 0] }
 })
+
 TestKeys(["throw", "function "], {
   keys: function() { return this.keys2() },
   keys2: function() { return ["throw", "function "] }
 })
+
 TestKeys(["[object Object]"], {
   get keys() {
     return function() { return [{}] }
   }
 })
+
 TestKeys(["a", "0"], {
   getOwnPropertyNames: function() { return ["a", 23, "zz", "", 0] },
   getOwnPropertyDescriptor: function(k) { return {enumerable: k.length == 1} }
 })
+
 TestKeys(["23", "zz", ""], {
   getOwnPropertyNames: function() { return this.getOwnPropertyNames2() },
   getOwnPropertyNames2: function() { return ["a", 23, "zz", "", 0] },
@@ -590,6 +712,7 @@
   },
   getOwnPropertyDescriptor2: function(k) { return {enumerable: k.length != 1} }
 })
+
 TestKeys(["a", "b", "c", "5"], {
   get getOwnPropertyNames() {
     return function() { return ["0", 4, "a", "b", "c", 5] }
@@ -598,6 +721,7 @@
     return function(k) { return {enumerable: k >= "44"} }
   }
 })
+
 TestKeys([], {
   get getOwnPropertyNames() {
     return function() { return ["a", "b", "c"] }
@@ -661,6 +785,7 @@
 TestFix([], {
   fix: function() { return {} }
 })
+
 TestFix(["a", "b", "c", "d", "zz"], {
   fix: function() {
     return {
@@ -672,12 +797,14 @@
     }
   }
 })
+
 TestFix(["a"], {
   fix: function() { return this.fix2() },
   fix2: function() {
     return {a: {value: 4, writable: true, configurable: true, enumerable: true}}
   }
 })
+
 TestFix(["b"], {
   get fix() {
     return function() {
@@ -685,3 +812,87 @@
     }
   }
 })
+
+
+
+// String conversion (Object.prototype.toString, Object.prototype.toLocaleString)
+
+var key
+function TestToString(handler) {
+  var o = Proxy.create(handler)
+  key = ""
+  assertEquals("[object Object]", Object.prototype.toString.call(o))
+  assertEquals("", key)
+  assertEquals("my_proxy", Object.prototype.toLocaleString.call(o))
+  assertEquals("toString", key)
+}
+
+TestToString({
+  get: function(r, k) { key = k; return function() { return "my_proxy" } }
+})
+
+TestToString({
+  get: function(r, k) { return this.get2(r, k) },
+  get2: function(r, k) { key = k; return function() { return "my_proxy" } }
+})
+
+TestToString(Proxy.create({
+  get: function(pr, pk) {
+    return function(r, k) { key = k; return function() { return "my_proxy" } }
+  }
+}))
+
+
+
+// Value conversion (Object.prototype.toValue)
+
+function TestValueOf(handler) {
+  var o = Proxy.create(handler)
+  assertSame(o, Object.prototype.valueOf.call(o))
+}
+
+TestValueOf({})
+
+
+
+// Enumerability (Object.prototype.propertyIsEnumerable)
+
+var key
+function TestIsEnumerable(handler) {
+  var o = Proxy.create(handler)
+  assertTrue(Object.prototype.propertyIsEnumerable.call(o, "a"))
+  assertEquals("a", key)
+  assertTrue(Object.prototype.propertyIsEnumerable.call(o, 2))
+  assertEquals("2", key)
+  assertFalse(Object.prototype.propertyIsEnumerable.call(o, "z"))
+  assertEquals("z", key)
+}
+
+TestIsEnumerable({
+  getOwnPropertyDescriptor: function(k) {
+    key = k; return {enumerable: k < "z", configurable: true}
+  },
+})
+
+TestIsEnumerable({
+  getOwnPropertyDescriptor: function(k) {
+    return this.getOwnPropertyDescriptor2(k)
+  },
+  getOwnPropertyDescriptor2: function(k) {
+    key = k; return {enumerable: k < "z", configurable: true}
+  },
+})
+
+TestIsEnumerable({
+  getOwnPropertyDescriptor: function(k) {
+    key = k; return {get enumerable() { return k < "z" }, configurable: true}
+  },
+})
+
+TestIsEnumerable(Proxy.create({
+  get: function(pr, pk) {
+    return function(k) {
+      key = k; return {enumerable: k < "z", configurable: true}
+    }
+  }
+}))
diff --git a/src/shell.h b/test/mjsunit/harmony/typeof.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/harmony/typeof.js
index ca51040..acde977 100644
--- a/src/shell.h
+++ b/test/mjsunit/harmony/typeof.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,12 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --harmony-typeof
 
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+assertFalse(typeof null == 'object')
+assertFalse(typeof null === 'object')
+assertTrue(typeof null == 'null')
+assertTrue(typeof null === 'null')
+assertEquals("null", typeof null)
+assertSame("null", typeof null)
diff --git a/test/mjsunit/harmony/weakmaps.js b/test/mjsunit/harmony/weakmaps.js
new file mode 100644
index 0000000..e43f916
--- /dev/null
+++ b/test/mjsunit/harmony/weakmaps.js
@@ -0,0 +1,163 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --harmony-weakmaps --expose-gc
+
+
+// Test valid getter and setter calls
+var m = new WeakMap;
+assertDoesNotThrow(function () { m.get(new Object) });
+assertDoesNotThrow(function () { m.set(new Object) });
+assertDoesNotThrow(function () { m.has(new Object) });
+assertDoesNotThrow(function () { m.delete(new Object) });
+
+
+// Test invalid getter and setter calls
+var m = new WeakMap;
+assertThrows(function () { m.get(undefined) }, TypeError);
+assertThrows(function () { m.set(undefined, 0) }, TypeError);
+assertThrows(function () { m.get(0) }, TypeError);
+assertThrows(function () { m.set(0, 0) }, TypeError);
+assertThrows(function () { m.get('a-key') }, TypeError);
+assertThrows(function () { m.set('a-key', 0) }, TypeError);
+
+
+// Test expected mapping behavior
+var m = new WeakMap;
+function TestMapping(map, key, value) {
+  map.set(key, value);
+  assertSame(value, map.get(key));
+}
+TestMapping(m, new Object, 23);
+TestMapping(m, new Object, 'the-value');
+TestMapping(m, new Object, new Object);
+
+
+// Test expected querying behavior
+var m = new WeakMap;
+var key = new Object;
+TestMapping(m, key, 'to-be-present');
+assertTrue(m.has(key));
+assertFalse(m.has(new Object));
+TestMapping(m, key, undefined);
+assertFalse(m.has(key));
+assertFalse(m.has(new Object));
+
+
+// Test expected deletion behavior
+var m = new WeakMap;
+var key = new Object;
+TestMapping(m, key, 'to-be-deleted');
+assertTrue(m.delete(key));
+assertFalse(m.delete(key));
+assertFalse(m.delete(new Object));
+assertSame(m.get(key), undefined);
+
+
+// Test GC of map with entry
+var m = new WeakMap;
+var key = new Object;
+m.set(key, 'not-collected');
+gc();
+assertSame('not-collected', m.get(key));
+
+
+// Test GC of map with chained entries
+var m = new WeakMap;
+var head = new Object;
+for (key = head, i = 0; i < 10; i++, key = m.get(key)) {
+  m.set(key, new Object);
+}
+gc();
+var count = 0;
+for (key = head; key != undefined; key = m.get(key)) {
+  count++;
+}
+assertEquals(11, count);
+
+
+// Test property attribute [[Enumerable]]
+var m = new WeakMap;
+function props(x) {
+  var array = [];
+  for (var p in x) array.push(p);
+  return array.sort();
+}
+assertArrayEquals([], props(WeakMap));
+assertArrayEquals([], props(WeakMap.prototype));
+assertArrayEquals([], props(m));
+
+
+// Test arbitrary properties on weak maps
+var m = new WeakMap;
+function TestProperty(map, property, value) {
+  map[property] = value;
+  assertEquals(value, map[property]);
+}
+for (i = 0; i < 20; i++) {
+  TestProperty(m, i, 'val' + i);
+  TestProperty(m, 'foo' + i, 'bar' + i);
+}
+TestMapping(m, new Object, 'foobar');
+
+
+// Test direct constructor call
+var m = WeakMap();
+assertTrue(m instanceof WeakMap);
+
+
+// Test some common JavaScript idioms
+var m = new WeakMap;
+assertTrue(m instanceof WeakMap);
+assertTrue(WeakMap.prototype.set instanceof Function)
+assertTrue(WeakMap.prototype.get instanceof Function)
+assertTrue(WeakMap.prototype.has instanceof Function)
+assertTrue(WeakMap.prototype.delete instanceof Function)
+assertTrue(WeakMap.prototype.constructor === WeakMap)
+
+
+// Regression test for issue 1617: The prototype of the WeakMap constructor
+// needs to be unique (i.e. different from the one of the Object constructor).
+assertFalse(WeakMap.prototype === Object.prototype);
+var o = Object.create({});
+assertFalse("get" in o);
+assertFalse("set" in o);
+assertEquals(undefined, o.get);
+assertEquals(undefined, o.set);
+var o = Object.create({}, { myValue: {
+  value: 10,
+  enumerable: false,
+  configurable: true,
+  writable: true
+}});
+assertEquals(10, o.myValue);
+
+
+// Stress Test
+// There is a proposed stress-test available at the es-discuss mailing list
+// which cannot be reasonably automated.  Check it out by hand if you like:
+// https://mail.mozilla.org/pipermail/es-discuss/2011-May/014096.html
diff --git a/test/mjsunit/math-floor.js b/test/mjsunit/math-floor.js
index 11f4cd7..f211ce2 100644
--- a/test/mjsunit/math-floor.js
+++ b/test/mjsunit/math-floor.js
@@ -27,10 +27,11 @@
 
 // Flags: --max-new-space-size=256 --allow-natives-syntax
 
+var test_id = 0;
+
 function testFloor(expect, input) {
-  function test(n) {
-    return Math.floor(n);
-  }
+  var test = new Function('n',
+                          '"' + (test_id++) + '";return Math.floor(n)');
   assertEquals(expect, test(input));
   assertEquals(expect, test(input));
   assertEquals(expect, test(input));
@@ -51,6 +52,17 @@
   testFloor(-Infinity, -Infinity);
   testFloor(NaN, NaN);
 
+  // Ensure that a negative zero coming from Math.floor is properly handled
+  // by other operations.
+  function ifloor(x) {
+    return 1 / Math.floor(x);
+  }
+  assertEquals(-Infinity, ifloor(-0));
+  assertEquals(-Infinity, ifloor(-0));
+  assertEquals(-Infinity, ifloor(-0));
+  %OptimizeFunctionOnNextCall(ifloor);
+  assertEquals(-Infinity, ifloor(-0));
+
   testFloor(0, 0.1);
   testFloor(0, 0.49999999999999994);
   testFloor(0, 0.5);
@@ -129,3 +141,19 @@
 for (var i = 0; i < 500; i++) {
   test();
 }
+
+
+// Regression test for a bug where a negative zero coming from Math.floor
+// was not properly handled by other operations.
+function floorsum(i, n) {
+  var ret = Math.floor(n);
+  while (--i > 0) {
+    ret += Math.floor(n);
+  }
+  return ret;
+}
+assertEquals(-0, floorsum(1, -0));
+%OptimizeFunctionOnNextCall(floorsum);
+// The optimized function will deopt.  Run it with enough iterations to try
+// to optimize via OSR (triggering the bug).
+assertEquals(-0, floorsum(100000, -0));
diff --git a/test/mjsunit/math-round.js b/test/mjsunit/math-round.js
index 1366557..102c970 100644
--- a/test/mjsunit/math-round.js
+++ b/test/mjsunit/math-round.js
@@ -1,4 +1,4 @@
-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -27,10 +27,12 @@
 
 // Flags: --allow-natives-syntax
 
+var test_id = 0;
 function testRound(expect, input) {
-  function doRound(input) {
-    return Math.round(input);
-  }
+  // Make source code different on each invocation to make
+  // sure it gets optimized each time.
+  var doRound = new Function('input',
+                             '"' + (test_id++) + '";return Math.round(input)');
   assertEquals(expect, doRound(input));
   assertEquals(expect, doRound(input));
   assertEquals(expect, doRound(input));
@@ -44,6 +46,21 @@
 testRound(-Infinity, -Infinity);
 testRound(NaN, NaN);
 
+// Regression test for a bug where a negative zero coming from Math.round
+// was not properly handled by other operations.
+function roundsum(i, n) {
+  var ret = Math.round(n);
+  while (--i > 0) {
+    ret += Math.round(n);
+  }
+  return ret;
+}
+assertEquals(-0, roundsum(1, -0));
+%OptimizeFunctionOnNextCall(roundsum);
+// The optimized function will deopt.  Run it with enough iterations to try
+// to optimize via OSR (triggering the bug).
+assertEquals(-0, roundsum(100000, -0));
+
 testRound(1, 0.5);
 testRound(1, 0.7);
 testRound(1, 1);
diff --git a/test/mjsunit/parse-int-float.js b/test/mjsunit/parse-int-float.js
index a4f09df..2e4f648 100644
--- a/test/mjsunit/parse-int-float.js
+++ b/test/mjsunit/parse-int-float.js
@@ -100,4 +100,17 @@
 assertEquals(Infinity, parseFloat(1/0), "parseFloat Infinity");
 assertEquals(-Infinity, parseFloat(-1/0), "parseFloat -Infinity");
 
+var state;
+var throwingRadix = { valueOf: function() { state = "throwingRadix"; throw null; } };
+var throwingString = { toString: function() { state = "throwingString"; throw null; } };
+state = null;
+try { parseInt('123', throwingRadix); } catch (e) {}
+assertEquals(state, "throwingRadix");
 
+state = null;
+try { parseInt(throwingString, 10); } catch (e) {}
+assertEquals(state, "throwingString");
+
+state = null;
+try { parseInt(throwingString, throwingRadix); } catch (e) {}
+assertEquals(state, "throwingString");
diff --git a/src/shell.h b/test/mjsunit/regress/regress-103259.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-103259.js
index ca51040..447073c 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-103259.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,13 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --allow-natives-syntax
 
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+var a = [];
+a[8192] = '';
+assertTrue(%HasDictionaryElements(a));
+var uc16 = '\u0094';
+var test = uc16;
+for (var i = 0; i < 13; i++) test += test;
+assertEquals(test, a.join(uc16));
diff --git a/src/shell.h b/test/mjsunit/regress/regress-1419.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-1419.js
index ca51040..98a8b76 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-1419.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,24 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Test that using bind several time does not change the length of existing
+// bound functions.
 
-#include "../public/debug.h"
+function foo() {
+}
 
-namespace v8 {
-namespace internal {
+var f1 = function (x) {}.bind(foo);
+var f2 = function () {};
 
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
+assertEquals(1, f1.length);
 
+// the object we bind to can be any object
+f2.bind(foo);
 
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
+assertEquals(1, f1.length);
 
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+var desc = Object.getOwnPropertyDescriptor(f1, 'length');
+assertEquals(false, desc.writable);
+assertEquals(false, desc.enumerable);
+assertEquals(false, desc.configurable);
diff --git a/src/shell.h b/test/mjsunit/regress/regress-1546.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-1546.js
index ca51040..7f1fa58 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-1546.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,9 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// See: http://code.google.com/p/v8/issues/detail?id=1546
 
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+// Should't throw. Scanner incorrectly truncated to char before comparing
+// with "*", so it ended the comment early.
+eval("/*\u822a/ */");
\ No newline at end of file
diff --git a/src/shell.h b/test/mjsunit/regress/regress-1563.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-1563.js
index ca51040..c25b6c7 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-1563.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,21 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --allow-natives-syntax
 
-#include "../public/debug.h"
+obj = new PixelArray(10);
 
-namespace v8 {
-namespace internal {
+// Test that undefined gets properly clamped in Crankshafted pixel array
+// assignments.
+function set_pixel(obj, arg) {
+  obj[0] = arg;
+}
 
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
+set_pixel(obj, 1.5);
+set_pixel(obj, NaN);
+%OptimizeFunctionOnNextCall(set_pixel);
+set_pixel(obj, undefined);
+set_pixel(obj, undefined);
 
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+assertEquals(0, obj[0]);
diff --git a/src/shell.h b/test/mjsunit/regress/regress-1586.js
similarity index 61%
copy from src/shell.h
copy to test/mjsunit/regress/regress-1586.js
index ca51040..b15e2f2 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-1586.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,41 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --expose-debug-as debug
 
-#include "../public/debug.h"
+// Test debug evaluation for functions without local context, but with
+// nested catch contexts.
 
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
+function f() {
+  var i = 1;          // Line 1.
+  {                   // Line 2.
+    try {             // Line 3.
+      throw 'stuff';  // Line 4.
+    } catch (e) {     // Line 5.
+      x = 2;          // Line 6.
+    }
+  }
 };
 
-} }  // namespace v8::internal
+// Get the Debug object exposed from the debug context global object.
+Debug = debug.Debug
+// Set breakpoint on line 6.
+var bp = Debug.setBreakPoint(f, 6);
 
-#endif  // V8_SHELL_H_
+function listener(event, exec_state, event_data, data) {
+  if (event == Debug.DebugEvent.Break) {
+    result = exec_state.frame().evaluate("i").value();
+  }
+};
+
+// Add the debug event listener.
+Debug.setListener(listener);
+result = -1;
+f();
+assertEquals(1, result);
+
+// Clear breakpoint.
+Debug.clearBreakPoint(bp);
+// Get rid of the debug event listener.
+Debug.setListener(null);
diff --git a/test/mjsunit/regress/regress-1620.js b/test/mjsunit/regress/regress-1620.js
new file mode 100644
index 0000000..6d72974
--- /dev/null
+++ b/test/mjsunit/regress/regress-1620.js
@@ -0,0 +1,54 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Don't allow malformed unicode escape sequences in identifiers.
+// In strings and regexps we currently allow malformed unicode escape
+// sequences without throwing a SyntaxError. Instead "\u22gk" would
+// treat the "\u" as an identity escape, and evaluate to "u22gk".
+// Due to code sharing, we did the same in identifiers. This should
+// no longer be the case.
+// See: http://code.google.com/p/v8/issues/detail?id=1620
+
+assertThrows("var \\u\\u\\u = 42;");
+assertThrows("var \\u41 = 42;");
+assertThrows("var \\u123 = 42;");
+eval("var \\u1234 = 42;");
+assertEquals(42, eval("\u1234"));
+assertThrows("var uuu = 42; var x = \\u\\u\\u");
+
+// Regressions introduced and fixed again while fixing the above.
+
+// Handle 0xFFFD correctly (it's a valid value, and shouldn't be used
+// to mark an error).
+assertEquals(0xFFFD, "\uFFFD".charCodeAt(0));
+
+// Handle unicode escapes in regexp flags correctly.
+assertThrows("/x/g\\uim", SyntaxError);
+assertThrows("/x/g\\u2im", SyntaxError);
+assertThrows("/x/g\\u22im", SyntaxError);
+assertThrows("/x/g\\u222im", SyntaxError);
+assertThrows("/x/g\\\\u2222im", SyntaxError);
diff --git a/src/shell.h b/test/mjsunit/regress/regress-1625.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-1625.js
index ca51040..a2ef8df 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-1625.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,13 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Test that overwriting Array.prototype.push does not make
+// Object.defineProperties misbehave.
 
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+Array.prototype.push = 1;
+var desc = {foo: {value: 10}, bar: {get: function() {return 42; }}};
+var obj = {};
+var x = Object.defineProperties(obj, desc);
+assertEquals(x.foo, 10);
+assertEquals(x.bar, 42);
diff --git a/test/mjsunit/regress/regress-219.js b/test/mjsunit/regress/regress-219.js
index 4bfabdc..b751f0f 100644
--- a/test/mjsunit/regress/regress-219.js
+++ b/test/mjsunit/regress/regress-219.js
@@ -30,6 +30,10 @@
 // We should now allow duplicates of flags.
 // (See http://code.google.com/p/v8/issues/detail?id=219)
 
+// This has been reversed by issue 1628, since other browsers have also
+// tightened their syntax.
+// (See http://code.google.com/p/v8/issues/detail?id=1628)
+
 // Base tests: we recognize the basic flags
 
 function assertFlags(re, global, multiline, ignoreCase) {
@@ -53,124 +57,92 @@
 
 // Double i's
 
-re = /a/ii;
-assertFlags(re, false, false, true)
+assertThrows("/a/ii");
 
-re = /a/gii;
-assertFlags(re, true, false, true)
+assertThrows("/a/gii");
 
-re = /a/igi;
-assertFlags(re, true, false, true)
+assertThrows("/a/igi");
 
-re = /a/iig;
-assertFlags(re, true, false, true)
+assertThrows("/a/iig");
 
-re = /a/gimi;
-assertFlags(re, true, true, true)
+assertThrows("/a/gimi");
 
-re = /a/giim;
-assertFlags(re, true, true, true)
+assertThrows("/a/giim");
 
-re = /a/igim;
-assertFlags(re, true, true, true)
+assertThrows("/a/igim");
 
+assertThrows(function(){ return RegExp("a", "ii"); })
 
-re = RegExp("a", "ii");
-assertFlags(re, false, false, true)
+assertThrows(function(){ return RegExp("a", "gii"); })
 
-re = RegExp("a", "gii");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "igi"); })
 
-re = RegExp("a", "igi");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "iig"); })
 
-re = RegExp("a", "iig");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "gimi"); })
 
-re = RegExp("a", "gimi");
-assertFlags(re, true, true, true)
+assertThrows(function(){ return RegExp("a", "giim"); })
 
-re = RegExp("a", "giim");
-assertFlags(re, true, true, true)
-
-re = RegExp("a", "igim");
-assertFlags(re, true, true, true)
+assertThrows(function(){ return RegExp("a", "igim"); })
 
 // Tripple i's
 
-re = /a/iii;
-assertFlags(re, false, false, true)
+assertThrows("/a/iii");
 
-re = /a/giii;
-assertFlags(re, true, false, true)
+assertThrows("/a/giii");
 
-re = /a/igii;
-assertFlags(re, true, false, true)
+assertThrows("/a/igii");
 
-re = /a/iigi;
-assertFlags(re, true, false, true)
+assertThrows("/a/iigi");
 
-re = /a/iiig;
-assertFlags(re, true, false, true)
+assertThrows("/a/iiig");
 
-re = /a/miiig;
-assertFlags(re, true, true, true)
+assertThrows("/a/miiig");
 
+assertThrows(function(){ return RegExp("a", "iii"); })
 
-re = RegExp("a", "iii");
-assertFlags(re, false, false, true)
+assertThrows(function(){ return RegExp("a", "giii"); })
 
-re = RegExp("a", "giii");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "igii"); })
 
-re = RegExp("a", "igii");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "iigi"); })
 
-re = RegExp("a", "iigi");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "iiig"); })
 
-re = RegExp("a", "iiig");
-assertFlags(re, true, false, true)
+assertThrows(function(){ return RegExp("a", "miiig"); })
 
-re = RegExp("a", "miiig");
-assertFlags(re, true, true, true)
+// Illegal flags - valid flags late in string.
 
-// Illegal flags - flags late in string.
+assertThrows("/a/arglebargleglopglyf");
 
-re = /a/arglebargleglopglyf;
-assertFlags(re, true, false, false)
+assertThrows("/a/arglebargleglopglif");
 
-re = /a/arglebargleglopglif;
-assertFlags(re, true, false, true)
+assertThrows("/a/arglebargleglopglym");
 
-re = /a/arglebargleglopglym;
-assertFlags(re, true, true, false)
-
-re = /a/arglebargleglopglim;
-assertFlags(re, true, true, true)
+assertThrows("/a/arglebargleglopglim");
 
 // Case of flags still matters.
 
-re = /a/gmi;
+var re = /a/gmi;
 assertFlags(re, true, true, true)
 
-re = /a/Gmi;
-assertFlags(re, false, true, true)
+assertThrows("/a/Gmi");
 
-re = /a/gMi;
-assertFlags(re, true, false, true)
+assertThrows("/a/gMi");
 
-re = /a/gmI;
-assertFlags(re, true, true, false)
+assertThrows("/a/gmI");
 
-re = /a/GMi;
-assertFlags(re, false, false, true)
+assertThrows("/a/GMi");
 
-re = /a/GmI;
-assertFlags(re, false, true, false)
+assertThrows("/a/GmI");
 
-re = /a/gMI;
-assertFlags(re, true, false, false)
+assertThrows("/a/gMI");
 
-re = /a/GMI;
-assertFlags(re, false, false, false)
+assertThrows("/a/GMI");
+
+// Unicode escape sequences are not interpreted.
+
+assertThrows("/a/\\u0067");
+assertThrows("/a/\\u0069");
+assertThrows("/a/\\u006d");
+assertThrows("/a/\\u006D");
diff --git a/test/mjsunit/regress/regress-87.js b/test/mjsunit/regress/regress-87.js
index 131cb58..10446fd 100644
--- a/test/mjsunit/regress/regress-87.js
+++ b/test/mjsunit/regress/regress-87.js
@@ -25,34 +25,29 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-function testFlags(flagstring, global, ignoreCase, multiline) {
-  var text = "/x/"+flagstring;
-  var re = eval(text);
-  assertEquals(global, re.global, text + ".global");
-  assertEquals(ignoreCase, re.ignoreCase, text + ".ignoreCase");
-  assertEquals(multiline, re.multiline, text + ".multiline");
-}
+// In Issue 87, we allowed unicode escape sequences in RegExp flags.
+// However, according to ES5, they should not be interpreted, but passed
+// verbatim to the RegExp constructor.
+// (On top of that, the original test was bugged and never tested anything).
+// The behavior was changed in r8969 to not interpret escapes, but this
+// test didn't test that, and only failed when making invalid flag characters
+// an error too.
 
-testFlags("", false, false, false);
+assertThrows("/x/\\u0067");
+assertThrows("/x/\\u0069");
+assertThrows("/x/\\u006d");
 
-testFlags("\u0067", true, false, false);
+assertThrows("/x/\\u0067i");
+assertThrows("/x/\\u0069m");
+assertThrows("/x/\\u006dg");
 
-testFlags("\u0069", false, true, false)
+assertThrows("/x/m\\u0067");
+assertThrows("/x/g\\u0069");
+assertThrows("/x/i\\u006d");
 
-testFlags("\u006d", false, false, true);
+assertThrows("/x/m\\u0067i");
+assertThrows("/x/g\\u0069m");
+assertThrows("/x/i\\u006dg");
 
-testFlags("\u0068", false, false, false);
-
-testFlags("\u0020", false, false, false);
-
-
-testFlags("\u0067g", true, false, false);
-
-testFlags("g\u0067", true, false, false);
-
-testFlags("abc\u0067efg", true, false, false);
-
-testFlags("i\u0067", true, true, false);
-
-testFlags("\u0067i", true, true, false);
-
+assertThrows("/x/\\u0068");
+assertThrows("/x/\\u0020");
diff --git a/src/shell.h b/test/mjsunit/regress/regress-91008.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-91008.js
index ca51040..d7ea2df 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-91008.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,20 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+function testsort(n) {
+  var numbers=new Array(n);
+  for (var i=0;i<n;i++) numbers[i]=i;
+  delete numbers[50];
+  delete numbers[150];
+  delete numbers[25000];
+  delete numbers[n-1];
+  delete numbers[n-2];
+  delete numbers[30];
+  delete numbers[2];
+  delete numbers[1];
+  delete numbers[0];
+  numbers.sort();
+}
 
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+testsort(100000)
diff --git a/src/shell.h b/test/mjsunit/regress/regress-91010.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-91010.js
index ca51040..a077999 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-91010.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,13 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
-
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+try {
+  try {
+    var N = 100*1000;
+    var array = Array(N);
+    for (var i = 0; i != N; ++i)
+      array[i] = i;
+  } catch(ex) {}
+  array.unshift('Kibo');
+} catch(ex) {}
diff --git a/src/shell.h b/test/mjsunit/regress/regress-91013.js
similarity index 66%
rename from src/shell.h
rename to test/mjsunit/regress/regress-91013.js
index ca51040..c61e2b1 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-91013.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,28 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Test that KeyedStore stub for unboxed double arrays backing store
+// correctly returns stored value as the result.
 
-#include "../public/debug.h"
+// Flags: --allow-natives-syntax --unbox-double-arrays
 
-namespace v8 {
-namespace internal {
+// Create array with unboxed double array backing store.
+var i = 100000;
+var a = new Array(i);
+for (var j = 0; j < i; j++) {
+  a[j] = 0.5;
+}
 
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
+assertTrue(%HasFastDoubleElements(a));
 
+// Store some smis into it.
+for (var j = 0; j < 10; j++) {
+  assertEquals(j, a[j] = j);
+}
 
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+// Store some heap numbers into it.
+for (var j = 0; j < 10; j++) {
+  var v = j + 0.5;
+  assertEquals(v, a[j] = v);
+}
diff --git a/src/shell.h b/test/mjsunit/regress/regress-95113.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-95113.js
index ca51040..f01b270 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-95113.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,25 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+// Flags: --allow-natives-syntax
 
-#include "../public/debug.h"
+function get_double_array() {
+  var a = new Array(100000);
+  var i = 0;
+  while (!%HasFastDoubleElements(a)) {
+    a[i] = i;
+    i++;
+  }
+  assertTrue(%HasFastDoubleElements(a));
+  a.length = 1;
+  a[0] = 1.5;
+  a.length = 2;
+  a[1] = 2.5;
+  assertEquals(a[0], 1.5);
+  assertEquals(a[1], 2.5);
+  assertTrue(%HasFastDoubleElements(a));
+  return a;
+}
 
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+var a = get_double_array();
diff --git a/src/shell.h b/test/mjsunit/regress/regress-95485.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-95485.js
index ca51040..2510072 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-95485.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,19 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
+function Test() {
+  var left  = 'XXX';
+  var right = 'YYY';
+  for (var i = 0; i < 3; i++) {
+    var cons = left + right;
+    var substring = cons.substring(2, 4);
+    try {
+      with ({Test: i})
+          continue;
+    } finally { }
+  }
+  return substring;
+}
 
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+assertEquals('XY', Test());
diff --git a/src/shell.h b/test/mjsunit/regress/regress-96523.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/regress/regress-96523.js
index ca51040..e611ce3 100644
--- a/src/shell.h
+++ b/test/mjsunit/regress/regress-96523.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,14 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
-
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
-
-
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SHELL_H_
+with ({x:'outer'}) {
+  (function() {
+    var x = 'inner';
+    try {
+      throw 'Exception';
+    } catch (e) {
+      assertEquals('inner', x);
+    }
+  })()
+}
diff --git a/src/shell.h b/test/mjsunit/scope-calls-eval.js
similarity index 66%
copy from src/shell.h
copy to test/mjsunit/scope-calls-eval.js
index ca51040..4a941aa 100644
--- a/src/shell.h
+++ b/test/mjsunit/scope-calls-eval.js
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -24,32 +24,42 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// A simple interactive shell.  Enable with --shell.
 
-#ifndef V8_SHELL_H_
-#define V8_SHELL_H_
-
-#include "../public/debug.h"
-
-namespace v8 {
-namespace internal {
-
-// Debug event handler for interactive debugging.
-void handle_debug_event(v8::DebugEvent event,
-                        v8::Handle<v8::Object> exec_state,
-                        v8::Handle<v8::Object> event_data,
-                        v8::Handle<Value> data);
+// Tests if the information about eval calls in a function is
+// propagated correctly through catch and with blocks.
 
 
-class Shell {
- public:
-  static void PrintObject(v8::Handle<v8::Value> obj);
-  // Run the read-eval loop, executing code in the specified
-  // environment.
-  static void Run(v8::Handle<v8::Context> context);
-};
+function f1() {
+  var x = 5;
+  function g() {
+    try {
+      throw '';
+    } catch (e) {
+      eval('var x = 3;');
+    }
+    try {
+      throw '';
+    } catch (e) {
+      return x;
+    }
+  }
+  return g();
+}
 
-} }  // namespace v8::internal
 
-#endif  // V8_SHELL_H_
+function f2() {
+  var x = 5;
+  function g() {
+    with ({e:42}) {
+      eval('var x = 3;');
+    }
+    with ({e:42}) {
+      return x;
+    }
+  }
+  return g();
+}
+
+
+assertEquals(3, f1());
+assertEquals(3, f2());
diff --git a/test/mjsunit/string-slices-regexp.js b/test/mjsunit/string-slices-regexp.js
new file mode 100644
index 0000000..a8cadae
--- /dev/null
+++ b/test/mjsunit/string-slices-regexp.js
@@ -0,0 +1,81 @@
+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Flags: --string-slices
+
+//assertEquals('345"12345 6"1234567"123',
+//             '12345""12345 6""1234567""1234'.slice(2,-1).replace(/""/g, '"'));
+
+var foo = "lsdfj sldkfj sdklfj læsdfjl sdkfjlsdk fjsdl fjsdljskdj flsj flsdkj flskd regexp: /foobar/\nldkfj sdlkfj sdkl";
+for(var i = 0; i < 1000; i++) {
+  assertTrue(/^([a-z]+): (.*)/.test(foo.substring(foo.indexOf("regexp:"))));
+  assertEquals("regexp", RegExp.$1, "RegExp.$1");
+}
+
+var re = /^(((N({)?)|(R)|(U)|(V)|(B)|(H)|(n((n)|(r)|(v)|(h))?)|(r(r)?)|(v)|(b((n)|(b))?)|(h))|((Y)|(A)|(E)|(o(u)?)|(p(u)?)|(q(u)?)|(s)|(t)|(u)|(w)|(x(u)?)|(y)|(z)|(a((T)|(A)|(L))?)|(c)|(e)|(f(u)?)|(g(u)?)|(i)|(j)|(l)|(m(u)?)))+/;
+var r = new RegExp(re)
+var str = "_Avtnennan gunzvmu pubExnY nEvln vaTxh rmuhguhaTxnY_".slice(1,-1);
+str = str + str;
+assertTrue(r.test(str));
+assertTrue(r.test(str));
+var re = /x/;
+assertEquals("a.yb", "_axyb_".slice(1,-1).replace(re, "."));
+re.compile("y");
+assertEquals("ax.b", "_axyb_".slice(1,-1).replace(re, "."));
+re.compile("(x)");
+assertEquals(["x", "x"], re.exec("_axyb_".slice(1,-1)));
+re.compile("(y)");
+assertEquals(["y", "y"], re.exec("_axyb_".slice(1,-1)));
+
+for(var i = 0; i < 100; i++) {
+  var a = "aaaaaaaaaaaaaaaaaaaaaaaabbaacabbabaaaaabbaaaabbac".slice(24,-1);
+  var b = "bbaacabbabaaaaabbaaaabba" + a;
+  // The first time, the cons string will be flattened and handled by the
+  // runtime system.
+  assertEquals(["bbaa", "a", "", "a"], /((\3|b)\2(a)){2,}/.exec(b));
+  // The second time, the cons string is already flattened and will be
+  // handled by generated code.
+  assertEquals(["bbaa", "a", "", "a"], /((\3|b)\2(a)){2,}/.exec(b));
+  assertEquals(["bbaa", "a", "", "a"], /((\3|b)\2(a)){2,}/.exec(a));
+  assertEquals(["bbaa", "a", "", "a"], /((\3|b)\2(a)){2,}/.exec(a));
+}
+
+var c = "ABCDEFGHIJKLMN".slice(2,-2);
+var d = "ABCDEF\u1234GHIJKLMN".slice(2,-2);
+var e = "ABCDEFGHIJKLMN".slice(0,-2);
+assertTrue(/^C.*L$/.test(c));
+assertTrue(/^C.*L$/.test(c));
+assertTrue(/^C.*L$/.test(d));
+assertTrue(/^C.*L$/.test(d));
+assertTrue(/^A\w{10}L$/.test(e));
+assertTrue(/^A\w{10}L$/.test(e));
+
+var e = "qui-opIasd-fghjklzx-cvbn-mqwer-tyuio-pasdf-ghIjkl-zx".slice(6,-6);
+var e_split = e.split("-");
+assertEquals(e_split[0], "Iasd");
+assertEquals(e_split[1], "fghjklzx");
+assertEquals(e_split[6], "ghI");
diff --git a/test/mjsunit/string-slices.js b/test/mjsunit/string-slices.js
new file mode 100755
index 0000000..f629ca9
--- /dev/null
+++ b/test/mjsunit/string-slices.js
@@ -0,0 +1,199 @@
+// Copyright 2008 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --string-slices --expose-externalize-string
+
+var s = 'abcdefghijklmn';
+assertEquals(s, s.substr());
+assertEquals(s, s.substr(0));
+assertEquals(s, s.substr('0'));
+assertEquals(s, s.substr(void 0));
+assertEquals(s, s.substr(null));
+assertEquals(s, s.substr(false));
+assertEquals(s, s.substr(0.9));
+assertEquals(s, s.substr({ valueOf: function() { return 0; } }));
+assertEquals(s, s.substr({ toString: function() { return '0'; } }));
+
+var s1 = s.substring(1);
+assertEquals(s1, s.substr(1));
+assertEquals(s1, s.substr('1'));
+assertEquals(s1, s.substr(true));
+assertEquals(s1, s.substr(1.1));
+assertEquals(s1, s.substr({ valueOf: function() { return 1; } }));
+assertEquals(s1, s.substr({ toString: function() { return '1'; } }));
+
+
+assertEquals(s.substring(s.length - 1), s.substr(-1));
+assertEquals(s.substring(s.length - 1), s.substr(-1.2));
+assertEquals(s.substring(s.length - 1), s.substr(-1.7));
+assertEquals(s.substring(s.length - 2), s.substr(-2));
+assertEquals(s.substring(s.length - 2), s.substr(-2.3));
+assertEquals(s.substring(s.length - 2, s.length - 1), s.substr(-2, 1));
+assertEquals(s, s.substr(-100));
+assertEquals('abc', s.substr(-100, 3));
+assertEquals(s1, s.substr(-s.length + 1));
+
+// assertEquals('', s.substr(0, void 0)); // smjs and rhino 
+assertEquals('abcdefghijklmn', s.substr(0, void 0));  // kjs and v8
+assertEquals('', s.substr(0, null));
+assertEquals(s, s.substr(0, String(s.length)));
+assertEquals('a', s.substr(0, true));
+
+
+// Test substrings of different lengths and alignments.
+// First ASCII.
+var x = "ASCII";
+for (var i = 0; i < 25; i++) {
+  x += (i >> 4).toString(16) + (i & 0x0f).toString(16);
+}
+/x/.exec(x);  // Try to force a flatten.
+for (var i = 5; i < 25; i++) {
+  for (var j = 0; j < 25; j++) {
+    var z = x.substring(i, i+j);
+    var w = Math.random() * 42;  // Allocate something new in new-space.
+    assertEquals(j, z.length);
+    for (var k = 0; k < j; k++) {
+      assertEquals(x.charAt(i+k), z.charAt(k));
+    }
+  }
+}
+// Then two-byte strings.
+x = "UC16\u2028";  // Non-ascii char forces two-byte string.
+for (var i = 0; i < 25; i++) {
+  x += (i >> 4).toString(16) + (i & 0x0f).toString(16);
+}
+/x/.exec(x);  // Try to force a flatten.
+for (var i = 5; i < 25; i++) {
+  for (var j = 0; j < 25; j++) {
+    var z = x.substring(i, i + j);
+    var w = Math.random() * 42;  // Allocate something new in new-space.
+    assertEquals(j, z.length);
+    for (var k = 0; k < j; k++) {
+      assertEquals(x.charAt(i+k), z.charAt(k));
+    }
+  }
+}
+
+// Keep creating strings to to force allocation failure on substring creation.
+var x = "0123456789ABCDEF";
+x += x;  // 2^5
+x += x;
+x += x;
+x += x;
+x += x;
+x += x;  // 2^10
+x += x;
+x += x;
+var xl = x.length;
+var cache = [];
+for (var i = 0; i < 1000; i++) {
+  var z = x.substring(i % xl);
+  assertEquals(xl - (i % xl), z.length);
+  cache.push(z);
+}
+
+
+// Same with two-byte strings
+var x = "\u2028123456789ABCDEF";
+x += x;  // 2^5
+x += x;
+x += x;
+x += x;
+x += x;
+x += x;  // 2^10
+x += x;
+x += x;
+var xl = x.length;
+var cache = [];
+for (var i = 0; i < 1000; i++) {
+  var z = x.substring(i % xl);
+  assertEquals(xl - (i % xl), z.length);
+  cache.push(z);
+}
+
+// Substring of substring.
+var cache = [];
+var last = x;
+var offset = 0;
+for (var i = 0; i < 64; i++) {
+  var z = last.substring(i);
+  last = z;
+  cache.push(z);
+  offset += i;
+}
+for (var i = 63; i >= 0; i--) {
+  var z = cache.pop();
+  assertTrue(/\u2028123456789ABCDEF/.test(z));
+  assertEquals(xl - offset, z.length);
+  assertEquals(x.charAt(i*(i+1)/2), z.charAt(0));
+  offset -= i;
+}
+
+// Test charAt for different strings.
+function f(s1, s2, s3, i) {
+  assertEquals(String.fromCharCode(97+i%11), s1.charAt(i%11));
+  assertEquals(String.fromCharCode(97+i%11), s2.charAt(i%11));
+  assertEquals(String.fromCharCode(98+i%11), s3.charAt(i%11));
+  assertEquals(String.fromCharCode(101), s3.charAt(3));
+}
+
+flat = "abcdefghijkl12345";
+cons = flat + flat.toUpperCase();
+slice = "abcdefghijklmn12345".slice(1, -1);
+for ( var i = 0; i < 1000; i++) {
+  f(flat, cons, slice, i);
+}
+flat = "abcdefghijkl1\u20232345";
+cons = flat + flat.toUpperCase();
+slice = "abcdefghijklmn1\u20232345".slice(1, -1);
+for ( var i = 0; i < 1000; i++) {
+  f(flat, cons, slice, i);
+}
+
+// Concatenate substrings.
+var ascii = 'abcdefghijklmnop';
+var utf = '\u03B1\u03B2\u03B3\u03B4\u03B5\u03B6\u03B7\u03B8\u03B9\u03BA\u03BB';
+assertEquals("klmno", ascii.substring(10,15) + ascii.substring(16));
+assertEquals("\u03B4\u03B7", utf.substring(3,4) + utf.substring(6,7));
+assertEquals("klp", ascii.substring(10,12) + ascii.substring(15,16));
+assertEquals("\u03B1\u03B4\u03B5", utf.substring(0,1) + utf.substring(5,3));
+assertEquals("", ascii.substring(16) + utf.substring(16));
+assertEquals("bcdef\u03B4\u03B5\u03B6\u03B7\u03B8\u03B9",
+    ascii.substring(1,6) + utf.substring(3,9));
+assertEquals("\u03B4\u03B5\u03B6\u03B7\u03B8\u03B9abcdefghijklmnop",
+    utf.substring(3,9) + ascii);
+assertEquals("\u03B2\u03B3\u03B4\u03B5\u03B4\u03B5\u03B6\u03B7",
+    utf.substring(5,1) + utf.substring(3,7));
+
+/*
+// Externalizing strings.
+var a = "123456789qwertyuiopasdfghjklzxcvbnm";
+var b = a.slice(1,-1);
+assertEquals(a.slice(1,-1), b);
+externalizeString(a);
+assertEquals(a.slice(1,-1), b);
+*/
\ No newline at end of file
diff --git a/test/mjsunit/string-split.js b/test/mjsunit/string-split.js
index 6fcf557..bc50945 100644
--- a/test/mjsunit/string-split.js
+++ b/test/mjsunit/string-split.js
@@ -116,3 +116,15 @@
 assertEquals(["a", "b", "c"], "abc".split("", numberObj(3)));
 assertEquals(["a", "b", "c"], "abc".split("", 4));
 assertEquals(["a", "b", "c"], "abc".split("", numberObj(4)));
+
+
+var all_ascii_codes = [];
+for (var i = 0; i < 128; i++) all_ascii_codes[i] = i;
+var all_ascii_string = String.fromCharCode.apply(String, all_ascii_codes);
+
+var split_chars = all_ascii_string.split("");
+assertEquals(128, split_chars.length);
+for (var i = 0; i < 128; i++) {
+  assertEquals(1, split_chars[i].length);
+  assertEquals(i, split_chars[i].charCodeAt(0));
+}
diff --git a/test/mjsunit/substr.js b/test/mjsunit/substr.js
index f69a9c0..cffaf94 100755
--- a/test/mjsunit/substr.js
+++ b/test/mjsunit/substr.js
@@ -135,3 +135,20 @@
   assertEquals(xl - (i % xl), z.length);
   cache.push(z);
 }
+
+// Substring of substring.
+var cache = [];
+var last = x;
+var offset = 0;
+for (var i = 0; i < 64; i++) {
+  var z = last.substring(i);
+  last = z;
+  cache.push(z);
+  offset += i;
+}
+for (var i = 63; i >= 0; i--) {
+  var z = cache.pop();
+  assertTrue(/\u2028123456789ABCDEF/.test(z));
+  assertEquals(xl - offset, z.length);
+  offset -= i;
+}
diff --git a/test/mjsunit/testcfg.py b/test/mjsunit/testcfg.py
index 7c6311b..87ed4fa 100644
--- a/test/mjsunit/testcfg.py
+++ b/test/mjsunit/testcfg.py
@@ -145,7 +145,7 @@
     return result
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     status_file = join(self.root, 'mjsunit.status')
diff --git a/test/mjsunit/unbox-double-arrays.js b/test/mjsunit/unbox-double-arrays.js
index 351765e..feecaec 100644
--- a/test/mjsunit/unbox-double-arrays.js
+++ b/test/mjsunit/unbox-double-arrays.js
@@ -29,12 +29,12 @@
 
 // Flags: --allow-natives-syntax --unbox-double-arrays --expose-gc
 var large_array_size = 100000;
-var approx_dict_to_elements_threshold = 75000;
+var approx_dict_to_elements_threshold = 70000;
 
 var name = 0;
 
 function expected_array_value(i) {
-  if ((i % 2) == 0) {
+  if ((i % 50) != 0) {
     return i;
   } else {
     return i + 0.5;
@@ -466,3 +466,62 @@
 test_for_in();
 test_for_in();
 test_for_in();
+
+function test_get_property_names() {
+  names = %GetPropertyNames(large_array3);
+  property_name_count = 0;
+  for (x in names) { property_name_count++; };
+  assertEquals(26, property_name_count);
+}
+
+test_get_property_names();
+test_get_property_names();
+test_get_property_names();
+
+// Test elements getters.
+assertEquals(expected_array_value(10), large_array3[10]);
+assertEquals(expected_array_value(-NaN), large_array3[2]);
+large_array3.__defineGetter__("2", function(){
+    return expected_array_value(10);
+});
+
+function test_getter() {
+  assertEquals(expected_array_value(10), large_array3[10]);
+  assertEquals(expected_array_value(10), large_array3[2]);
+}
+
+test_getter();
+test_getter();
+test_getter();
+%OptimizeFunctionOnNextCall(test_getter);
+test_getter();
+test_getter();
+test_getter();
+
+// Test element setters.
+large_array4 = new Array(large_array_size);
+force_to_fast_double_array(large_array4);
+
+var setter_called = false;
+
+assertEquals(expected_array_value(10), large_array4[10]);
+assertEquals(expected_array_value(2), large_array4[2]);
+large_array4.__defineSetter__("10", function(value){
+    setter_called = true;
+  });
+
+function test_setter() {
+  setter_called = false;
+  large_array4[10] = 119;
+  assertTrue(setter_called);
+  assertEquals(undefined, large_array4[10]);
+  assertEquals(expected_array_value(2), large_array4[2]);
+}
+
+test_setter();
+test_setter();
+test_setter();
+%OptimizeFunctionOnNextCall(test_setter);
+test_setter();
+test_setter();
+test_setter();
diff --git a/test/mjsunit/with-leave.js b/test/mjsunit/with-leave.js
index ded62ca..7369faa 100644
--- a/test/mjsunit/with-leave.js
+++ b/test/mjsunit/with-leave.js
@@ -1,4 +1,4 @@
-// Copyright 2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -59,3 +59,162 @@
 }
 assertTrue(caught);
 
+
+// We want to test the context chain shape.  In each of the tests cases
+// below, the outer with is to force a runtime lookup of the identifier 'x'
+// to actually verify that the inner context has been discarded.  A static
+// lookup of 'x' might accidentally succeed.
+with ({x: 'outer'}) {
+  label: {
+    with ({x: 'inner'}) {
+      break label;
+    }
+  }
+  assertEquals('outer', x);
+}
+
+
+with ({x: 'outer'}) {
+  label: {
+    with ({x: 'middle'}) {
+      with ({x: 'inner'}) {
+        break label;
+      }
+    }
+  }
+  assertEquals('outer', x);
+}
+
+
+with ({x: 'outer'}) {
+  for (var i = 0; i < 10; ++i) {
+    with ({x: 'inner' + i}) {
+      continue;
+    }
+  }
+  assertEquals('outer', x);
+}
+
+
+with ({x: 'outer'}) {
+  label: for (var i = 0; i < 10; ++i) {
+    with ({x: 'middle' + i}) {
+      for (var j = 0; j < 10; ++j) {
+        with ({x: 'inner' + j}) {
+          continue label;
+        }
+      }
+    }
+  }
+  assertEquals('outer', x);
+}
+
+
+with ({x: 'outer'}) {
+  try {
+    with ({x: 'inner'}) {
+      throw 0;
+    }
+  } catch (e) {
+    assertEquals('outer', x);
+  }
+}
+
+
+with ({x: 'outer'}) {
+  try {
+    with ({x: 'middle'}) {
+      with ({x: 'inner'}) {
+        throw 0;
+      }
+    }
+  } catch (e) {
+    assertEquals('outer', x);
+  }
+}
+
+
+try {
+  with ({x: 'outer'}) {
+    try {
+      with ({x: 'inner'}) {
+        throw 0;
+      }
+    } finally {
+      assertEquals('outer', x);
+    }
+  }
+} catch (e) {
+  if (e instanceof MjsUnitAssertionError) throw e;
+}
+
+
+try {
+  with ({x: 'outer'}) {
+    try {
+      with ({x: 'middle'}) {
+        with ({x: 'inner'}) {
+          throw 0;
+        }
+      }
+    } finally {
+      assertEquals('outer', x);
+    }
+  }
+} catch (e) {
+  if (e instanceof MjsUnitAssertionError) throw e;
+}
+
+
+// Verify that the context is correctly set in the stack frame after exiting
+// from with.
+function f() {}
+
+with ({x: 'outer'}) {
+  label: {
+    with ({x: 'inner'}) {
+      break label;
+    }
+  }
+  f();  // The context could be restored from the stack after the call.
+  assertEquals('outer', x);
+}
+
+
+with ({x: 'outer'}) {
+  for (var i = 0; i < 10; ++i) {
+    with ({x: 'inner' + i}) {
+      continue;
+    }
+  }
+  f();
+  assertEquals('outer', x);
+}
+
+
+with ({x: 'outer'}) {
+  try {
+    with ({x: 'inner'}) {
+      throw 0;
+    }
+  } catch (e) {
+    f();
+    assertEquals('outer', x);
+  }
+}
+
+
+try {
+  with ({x: 'outer'}) {
+    try {
+      with ({x: 'inner'}) {
+        throw 0;
+      }
+    } finally {
+      f();
+      assertEquals('outer', x);
+    }
+  }
+} catch (e) {
+  if (e instanceof MjsUnitAssertionError) throw e;
+}
diff --git a/test/mozilla/mozilla.status b/test/mozilla/mozilla.status
index c62d770..f6d6925 100644
--- a/test/mozilla/mozilla.status
+++ b/test/mozilla/mozilla.status
@@ -246,9 +246,8 @@
 ecma_3/Number/15.7.4.6-1: FAIL_OK
 
 #:=== RegExp:=== 
-# To be compatible with JSC we silently ignore flags that do not make
-# sense.  These tests expects us to throw exceptions.  
-ecma_3/RegExp/regress-57631: FAIL_OK
+# We don't match the syntax error message of Mozilla for invalid
+# RegExp flags.
 ecma_3/RegExp/15.10.4.1-6: FAIL_OK
 
 # PCRE doesn't allow subpattern nesting deeper than 200, this tests
diff --git a/test/mozilla/testcfg.py b/test/mozilla/testcfg.py
index 3728f79..587781d 100644
--- a/test/mozilla/testcfg.py
+++ b/test/mozilla/testcfg.py
@@ -125,7 +125,7 @@
     return tests
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     status_file = join(self.root, 'mozilla.status')
diff --git a/test/preparser/testcfg.py b/test/preparser/testcfg.py
index 39b62c3..d900e26 100644
--- a/test/preparser/testcfg.py
+++ b/test/preparser/testcfg.py
@@ -27,7 +27,7 @@
 
 import test
 import os
-from os.path import join, dirname, exists
+from os.path import join, dirname, exists, isfile
 import platform
 import utils
 import re
@@ -122,10 +122,15 @@
          {"Test": Test, "Template": Template}, {})
 
   def ListTests(self, current_path, path, mode, variant_flags):
-    executable = join('obj', 'preparser', mode, 'preparser')
+    executable = 'preparser'
     if utils.IsWindows():
       executable += '.exe'
     executable = join(self.context.buildspace, executable)
+    if not isfile(executable):
+      executable = join('obj', 'preparser', mode, 'preparser')
+      if utils.IsWindows():
+        executable += '.exe'
+      executable = join(self.context.buildspace, executable)
     expectations = self.GetExpectations()
     result = []
     # Find all .js files in tests/preparser directory.
diff --git a/test/sputnik/sputnik.status b/test/sputnik/sputnik.status
index 82d8a61..868509d 100644
--- a/test/sputnik/sputnik.status
+++ b/test/sputnik/sputnik.status
@@ -56,15 +56,6 @@
 # errors, for compatibility.
 S15.10.2.11_A1_T2: FAIL
 S15.10.2.11_A1_T3: FAIL
-S15.10.4.1_A5_T1: FAIL
-S15.10.4.1_A5_T2: FAIL
-S15.10.4.1_A5_T3: FAIL
-S15.10.4.1_A5_T4: FAIL
-S15.10.4.1_A5_T5: FAIL
-S15.10.4.1_A5_T6: FAIL
-S15.10.4.1_A5_T7: FAIL
-S15.10.4.1_A5_T8: FAIL
-S15.10.4.1_A5_T9: FAIL
 
 # We are more lenient in which string character escapes we allow than
 # the spec (7.8.4 p. 19) wants us to be.  This is for compatibility.
@@ -99,6 +90,13 @@
 S7.8.4_A4.3_T5: FAIL_OK
 S7.8.4_A7.2_T5: FAIL_OK
 
+# Sputnik expects unicode escape sequences in RegExp flags to be interpreted.
+# The specification requires them to be passed uninterpreted to the RegExp
+# constructor. We now implement that.
+S7.8.5_A3.1_T7: FAIL_OK
+S7.8.5_A3.1_T8: FAIL_OK
+S7.8.5_A3.1_T9: FAIL_OK
+
 # We allow some keywords to be used as identifiers.
 S7.5.3_A1.15: FAIL_OK
 S7.5.3_A1.18: FAIL_OK
diff --git a/test/sputnik/testcfg.py b/test/sputnik/testcfg.py
index c9eb4f2..1032c13 100644
--- a/test/sputnik/testcfg.py
+++ b/test/sputnik/testcfg.py
@@ -101,7 +101,7 @@
     return result
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     status_file = join(self.root, 'sputnik.status')
diff --git a/test/test262/testcfg.py b/test/test262/testcfg.py
index aa1212e..9482046 100644
--- a/test/test262/testcfg.py
+++ b/test/test262/testcfg.py
@@ -111,7 +111,7 @@
     return tests
 
   def GetBuildRequirements(self):
-    return ['sample', 'sample=shell']
+    return ['d8']
 
   def GetTestStatus(self, sections, defs):
     status_file = join(self.root, 'test262.status')
diff --git a/tools/grokdump.py b/tools/grokdump.py
index 468e7cc..6bc49c6 100755
--- a/tools/grokdump.py
+++ b/tools/grokdump.py
@@ -345,7 +345,7 @@
       for r in self.memory_list64.ranges:
         if r.start <= address < r.start + r.size:
           return self.memory_list64.base_rva + offset + address - r.start
-      offset += r.size
+        offset += r.size
     if self.memory_list is not None:
       for r in self.memory_list.ranges:
         if r.start <= address < r.start + r.memory.data_size:
@@ -379,64 +379,65 @@
 # };
 # static P p;
 INSTANCE_TYPES = {
-64: "SYMBOL_TYPE",
-68: "ASCII_SYMBOL_TYPE",
-65: "CONS_SYMBOL_TYPE",
-69: "CONS_ASCII_SYMBOL_TYPE",
-66: "EXTERNAL_SYMBOL_TYPE",
-74: "EXTERNAL_SYMBOL_WITH_ASCII_DATA_TYPE",
-70: "EXTERNAL_ASCII_SYMBOL_TYPE",
-0: "STRING_TYPE",
-4: "ASCII_STRING_TYPE",
-1: "CONS_STRING_TYPE",
-5: "CONS_ASCII_STRING_TYPE",
-2: "EXTERNAL_STRING_TYPE",
-10: "EXTERNAL_STRING_WITH_ASCII_DATA_TYPE",
-6: "EXTERNAL_ASCII_STRING_TYPE",
-6: "PRIVATE_EXTERNAL_ASCII_STRING_TYPE",
-128: "MAP_TYPE",
-129: "CODE_TYPE",
-130: "ODDBALL_TYPE",
-131: "JS_GLOBAL_PROPERTY_CELL_TYPE",
-132: "HEAP_NUMBER_TYPE",
-133: "FOREIGN_TYPE",
-134: "BYTE_ARRAY_TYPE",
-135: "EXTERNAL_BYTE_ARRAY_TYPE",
-136: "EXTERNAL_UNSIGNED_BYTE_ARRAY_TYPE",
-137: "EXTERNAL_SHORT_ARRAY_TYPE",
-138: "EXTERNAL_UNSIGNED_SHORT_ARRAY_TYPE",
-139: "EXTERNAL_INT_ARRAY_TYPE",
-140: "EXTERNAL_UNSIGNED_INT_ARRAY_TYPE",
-141: "EXTERNAL_FLOAT_ARRAY_TYPE",
-143: "EXTERNAL_PIXEL_ARRAY_TYPE",
-145: "FILLER_TYPE",
-146: "ACCESSOR_INFO_TYPE",
-147: "ACCESS_CHECK_INFO_TYPE",
-148: "INTERCEPTOR_INFO_TYPE",
-149: "CALL_HANDLER_INFO_TYPE",
-150: "FUNCTION_TEMPLATE_INFO_TYPE",
-151: "OBJECT_TEMPLATE_INFO_TYPE",
-152: "SIGNATURE_INFO_TYPE",
-153: "TYPE_SWITCH_INFO_TYPE",
-154: "SCRIPT_TYPE",
-155: "CODE_CACHE_TYPE",
-156: "POLYMORPHIC_CODE_CACHE_TYPE",
-159: "FIXED_ARRAY_TYPE",
-160: "SHARED_FUNCTION_INFO_TYPE",
-161: "JS_MESSAGE_OBJECT_TYPE",
-162: "JS_VALUE_TYPE",
-163: "JS_OBJECT_TYPE",
-164: "JS_CONTEXT_EXTENSION_OBJECT_TYPE",
-165: "JS_GLOBAL_OBJECT_TYPE",
-166: "JS_BUILTINS_OBJECT_TYPE",
-167: "JS_GLOBAL_PROXY_TYPE",
-168: "JS_ARRAY_TYPE",
-169: "JS_PROXY_TYPE",
-170: "JS_REGEXP_TYPE",
-171: "JS_FUNCTION_TYPE",
-172: "JS_FUNCTION_PROXY_TYPE",
-157: "DEBUG_INFO_TYPE",
-158: "BREAK_POINT_INFO_TYPE",
+  64: "SYMBOL_TYPE",
+  68: "ASCII_SYMBOL_TYPE",
+  65: "CONS_SYMBOL_TYPE",
+  69: "CONS_ASCII_SYMBOL_TYPE",
+  66: "EXTERNAL_SYMBOL_TYPE",
+  74: "EXTERNAL_SYMBOL_WITH_ASCII_DATA_TYPE",
+  70: "EXTERNAL_ASCII_SYMBOL_TYPE",
+  0: "STRING_TYPE",
+  4: "ASCII_STRING_TYPE",
+  1: "CONS_STRING_TYPE",
+  5: "CONS_ASCII_STRING_TYPE",
+  2: "EXTERNAL_STRING_TYPE",
+  10: "EXTERNAL_STRING_WITH_ASCII_DATA_TYPE",
+  6: "EXTERNAL_ASCII_STRING_TYPE",
+  6: "PRIVATE_EXTERNAL_ASCII_STRING_TYPE",
+  128: "MAP_TYPE",
+  129: "CODE_TYPE",
+  130: "ODDBALL_TYPE",
+  131: "JS_GLOBAL_PROPERTY_CELL_TYPE",
+  132: "HEAP_NUMBER_TYPE",
+  133: "FOREIGN_TYPE",
+  134: "BYTE_ARRAY_TYPE",
+  135: "EXTERNAL_BYTE_ARRAY_TYPE",
+  136: "EXTERNAL_UNSIGNED_BYTE_ARRAY_TYPE",
+  137: "EXTERNAL_SHORT_ARRAY_TYPE",
+  138: "EXTERNAL_UNSIGNED_SHORT_ARRAY_TYPE",
+  139: "EXTERNAL_INT_ARRAY_TYPE",
+  140: "EXTERNAL_UNSIGNED_INT_ARRAY_TYPE",
+  141: "EXTERNAL_FLOAT_ARRAY_TYPE",
+  143: "EXTERNAL_PIXEL_ARRAY_TYPE",
+  145: "FILLER_TYPE",
+  146: "ACCESSOR_INFO_TYPE",
+  147: "ACCESS_CHECK_INFO_TYPE",
+  148: "INTERCEPTOR_INFO_TYPE",
+  149: "CALL_HANDLER_INFO_TYPE",
+  150: "FUNCTION_TEMPLATE_INFO_TYPE",
+  151: "OBJECT_TEMPLATE_INFO_TYPE",
+  152: "SIGNATURE_INFO_TYPE",
+  153: "TYPE_SWITCH_INFO_TYPE",
+  154: "SCRIPT_TYPE",
+  155: "CODE_CACHE_TYPE",
+  156: "POLYMORPHIC_CODE_CACHE_TYPE",
+  159: "FIXED_ARRAY_TYPE",
+  160: "SHARED_FUNCTION_INFO_TYPE",
+  161: "JS_MESSAGE_OBJECT_TYPE",
+  162: "JS_VALUE_TYPE",
+  163: "JS_OBJECT_TYPE",
+  164: "JS_CONTEXT_EXTENSION_OBJECT_TYPE",
+  165: "JS_GLOBAL_OBJECT_TYPE",
+  166: "JS_BUILTINS_OBJECT_TYPE",
+  167: "JS_GLOBAL_PROXY_TYPE",
+  168: "JS_ARRAY_TYPE",
+  169: "JS_PROXY_TYPE",
+  170: "JS_WEAK_MAP_TYPE",
+  171: "JS_REGEXP_TYPE",
+  172: "JS_FUNCTION_TYPE",
+  173: "JS_FUNCTION_PROXY_TYPE",
+  157: "DEBUG_INFO_TYPE",
+  158: "BREAK_POINT_INFO_TYPE",
 }
 
 
diff --git a/tools/gyp/v8.gyp b/tools/gyp/v8.gyp
index 2650483..2da8213 100644
--- a/tools/gyp/v8.gyp
+++ b/tools/gyp/v8.gyp
@@ -26,211 +26,18 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 {
-  'variables': {
-    'use_system_v8%': 0,
-    'msvs_use_common_release': 0,
-    'gcc_version%': 'unknown',
-    'v8_compress_startup_data%': 'off',
-    'v8_target_arch%': '<(target_arch)',
-
-    # Setting 'v8_can_use_unaligned_accesses' to 'true' will allow the code
-    # generated by V8 to do unaligned memory access, and setting it to 'false'
-    # will ensure that the generated code will always do aligned memory
-    # accesses. The default value of 'default' will try to determine the correct
-    # setting. Note that for Intel architectures (ia32 and x64) unaligned memory
-    # access is allowed for all CPUs.
-    'v8_can_use_unaligned_accesses%': 'default',
-
-    # Setting 'v8_can_use_vfp_instructions' to 'true' will enable use of ARM VFP
-    # instructions in the V8 generated code. VFP instructions will be enabled
-    # both for the snapshot and for the ARM target. Leaving the default value
-    # of 'false' will avoid VFP instructions in the snapshot and use CPU feature
-    # probing when running on the target.
-    'v8_can_use_vfp_instructions%': 'false',
-
-    # Setting v8_use_arm_eabi_hardfloat to true will turn on V8 support for ARM
-    # EABI calling convention where double arguments are passed in VFP
-    # registers. Note that the GCC flag '-mfloat-abi=hard' should be used as
-    # well when compiling for the ARM target.
-    'v8_use_arm_eabi_hardfloat%': 'false',
-
-    'v8_use_snapshot%': 'true',
-    'host_os%': '<(OS)',
-    'v8_use_liveobjectlist%': 'false',
-  },
+  'includes': ['../../build/common.gypi'],
   'conditions': [
     ['use_system_v8==0', {
-      'target_defaults': {
-        'defines': [
-          'ENABLE_DEBUGGER_SUPPORT',
-        ],
-        'conditions': [
-          ['OS!="mac"', {
-            # TODO(mark): The OS!="mac" conditional is temporary. It can be
-            # removed once the Mac Chromium build stops setting target_arch to
-            # ia32 and instead sets it to mac. Other checks in this file for
-            # OS=="mac" can be removed at that time as well. This can be cleaned
-            # up once http://crbug.com/44205 is fixed.
-            'conditions': [
-              ['v8_target_arch=="arm"', {
-                'defines': [
-                  'V8_TARGET_ARCH_ARM',
-                ],
-                'conditions': [
-                  [ 'v8_can_use_unaligned_accesses=="true"', {
-                    'defines': [
-                      'CAN_USE_UNALIGNED_ACCESSES=1',
-                    ],
-                  }],
-                  [ 'v8_can_use_unaligned_accesses=="false"', {
-                    'defines': [
-                      'CAN_USE_UNALIGNED_ACCESSES=0',
-                    ],
-                  }],
-                  [ 'v8_can_use_vfp_instructions=="true"', {
-                    'defines': [
-                      'CAN_USE_VFP_INSTRUCTIONS',
-                    ],
-                  }],
-                  [ 'v8_use_arm_eabi_hardfloat=="true"', {
-                    'defines': [
-                      'USE_EABI_HARDFLOAT=1',
-                      'CAN_USE_VFP_INSTRUCTIONS',
-                    ],
-                  }],
-                ],
-              }],
-              ['v8_target_arch=="ia32"', {
-                'defines': [
-                  'V8_TARGET_ARCH_IA32',
-                ],
-              }],
-              ['v8_target_arch=="x64"', {
-                'defines': [
-                  'V8_TARGET_ARCH_X64',
-                ],
-              }],
-            ],
-          }],
-          ['v8_use_liveobjectlist=="true"', {
-            'defines': [
-              'ENABLE_DEBUGGER_SUPPORT',
-              'INSPECTOR',
-              'OBJECT_PRINT',
-              'LIVEOBJECTLIST',
-            ],
-          }],
-         ['v8_compress_startup_data=="bz2"', {
-            'defines': [
-              'COMPRESS_STARTUP_DATA_BZ2',
-            ],
-          }],
-        ],
-        'configurations': {
-          'Debug': {
-            'defines': [
-              'DEBUG',
-              '_DEBUG',
-              'ENABLE_DISASSEMBLER',
-              'V8_ENABLE_CHECKS',
-              'OBJECT_PRINT',
-            ],
-            'msvs_settings': {
-              'VCCLCompilerTool': {
-                'Optimization': '0',
-
-                'conditions': [
-                  ['OS=="win" and component=="shared_library"', {
-                    'RuntimeLibrary': '3',  # /MDd
-                  }, {
-                    'RuntimeLibrary': '1',  # /MTd
-                  }],
-                ],
-              },
-              'VCLinkerTool': {
-                'LinkIncremental': '2',
-              },
-            },
-            'conditions': [
-             ['OS=="freebsd" or OS=="openbsd"', {
-               'cflags': [ '-I/usr/local/include' ],
-             }],
-           ],
-          },
-          'Release': {
-            'conditions': [
-              ['OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
-                'cflags!': [
-                  '-O2',
-                  '-Os',
-                ],
-                'cflags': [
-                  '-fomit-frame-pointer',
-                  '-O3',
-                ],
-                'conditions': [
-                  [ 'gcc_version==44', {
-                    'cflags': [
-                      # Avoid crashes with gcc 4.4 in the v8 test suite.
-                      '-fno-tree-vrp',
-                    ],
-                  }],
-                ],
-              }],
-             ['OS=="freebsd" or OS=="openbsd"', {
-               'cflags': [ '-I/usr/local/include' ],
-             }],
-              ['OS=="mac"', {
-                'xcode_settings': {
-                  'GCC_OPTIMIZATION_LEVEL': '3',  # -O3
-
-                  # -fstrict-aliasing.  Mainline gcc
-                  # enables this at -O2 and above,
-                  # but Apple gcc does not unless it
-                  # is specified explicitly.
-                  'GCC_STRICT_ALIASING': 'YES',
-                },
-              }],
-              ['OS=="win"', {
-                'msvs_configuration_attributes': {
-                  'OutputDirectory': '$(SolutionDir)$(ConfigurationName)',
-                  'IntermediateDirectory': '$(OutDir)\\obj\\$(ProjectName)',
-                  'CharacterSet': '1',
-                },
-                'msvs_settings': {
-                  'VCCLCompilerTool': {
-                    'Optimization': '2',
-                    'InlineFunctionExpansion': '2',
-                    'EnableIntrinsicFunctions': 'true',
-                    'FavorSizeOrSpeed': '0',
-                    'OmitFramePointers': 'true',
-                    'StringPooling': 'true',
-
-                    'conditions': [
-                      ['OS=="win" and component=="shared_library"', {
-                        'RuntimeLibrary': '2',  #/MD
-                      }, {
-                        'RuntimeLibrary': '0',  #/MT
-                      }],
-                    ],
-                  },
-                  'VCLinkerTool': {
-                    'LinkIncremental': '1',
-                    'OptimizeReferences': '2',
-                    'OptimizeForWindows98': '1',
-                    'EnableCOMDATFolding': '2',
-                  },
-                },
-              }],
-            ],
-          },
-        },
-      },
       'targets': [
         {
           'target_name': 'v8',
-          'toolsets': ['host', 'target'],
           'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host', 'target'],
+            }, {
+              'toolsets': ['target'],
+            }],
             ['v8_use_snapshot=="true"', {
               'dependencies': ['v8_snapshot'],
             },
@@ -272,23 +79,23 @@
           ],
           'direct_dependent_settings': {
             'include_dirs': [
-               '../../include',
+              '../../include',
             ],
           },
         },
         {
           'target_name': 'v8_snapshot',
           'type': '<(library)',
-          'toolsets': ['host', 'target'],
           'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host', 'target'],
+              'dependencies': ['mksnapshot#host', 'js2c#host'],
+            }, {
+              'toolsets': ['target'],
+              'dependencies': ['mksnapshot', 'js2c'],
+            }],
             ['component=="shared_library"', {
               'conditions': [
-                # The ARM assembler assumes the host is 32 bits, so force building
-                # 32-bit host tools.
-                ['v8_target_arch=="arm" and host_arch=="x64" and _toolset=="host"', {
-                  'cflags': ['-m32'],
-                  'ldflags': ['-m32'],
-                }],
                 ['OS=="win"', {
                   'defines': [
                     'BUILDING_V8_SHARED',
@@ -312,8 +119,6 @@
             }],
           ],
           'dependencies': [
-            'mksnapshot#host',
-            'js2c#host',
             'v8_base',
           ],
           'include_dirs+': [
@@ -334,7 +139,10 @@
                 '<(INTERMEDIATE_DIR)/snapshot.cc',
               ],
               'variables': {
-                'mksnapshot_flags': [],
+                'mksnapshot_flags': [
+                  '--log-snapshot-positions',
+                  '--logfile', '<(INTERMEDIATE_DIR)/snapshot.log',
+                ],
               },
               'conditions': [
                 ['v8_target_arch=="arm"', {
@@ -380,9 +188,7 @@
         {
           'target_name': 'v8_nosnapshot',
           'type': '<(library)',
-          'toolsets': ['host', 'target'],
           'dependencies': [
-            'js2c#host',
             'v8_base',
           ],
           'include_dirs+': [
@@ -394,11 +200,12 @@
             '../../src/snapshot-empty.cc',
           ],
           'conditions': [
-            # The ARM assembler assumes the host is 32 bits, so force building
-            # 32-bit host tools.
-            ['v8_target_arch=="arm" and host_arch=="x64" and _toolset=="host"', {
-              'cflags': ['-m32'],
-              'ldflags': ['-m32'],
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host', 'target'],
+              'dependencies': ['js2c#host'],
+            }, {
+              'toolsets': ['target'],
+              'dependencies': ['js2c'],
             }],
             ['component=="shared_library"', {
               'defines': [
@@ -411,7 +218,6 @@
         {
           'target_name': 'v8_base',
           'type': '<(library)',
-          'toolsets': ['host', 'target'],
           'include_dirs+': [
             '../../src',
           ],
@@ -451,7 +257,6 @@
             '../../src/code-stubs.cc',
             '../../src/code-stubs.h',
             '../../src/code.h',
-            '../../src/codegen-inl.h',
             '../../src/codegen.cc',
             '../../src/codegen.h',
             '../../src/compilation-cache.cc',
@@ -488,6 +293,8 @@
             '../../src/diy-fp.cc',
             '../../src/diy-fp.h',
             '../../src/double.h',
+            '../../src/elements.cc',
+            '../../src/elements.h',
             '../../src/execution.cc',
             '../../src/execution.h',
             '../../src/factory.cc',
@@ -610,7 +417,6 @@
             '../../src/scopes.h',
             '../../src/serialize.cc',
             '../../src/serialize.h',
-            '../../src/shell.h',
             '../../src/small-pointer-list.h',
             '../../src/smart-pointer.h',
             '../../src/snapshot-common.cc',
@@ -666,10 +472,12 @@
             '../../src/extensions/gc-extension.h',
           ],
           'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host', 'target'],
+            }, {
+              'toolsets': ['target'],
+            }],
             ['v8_target_arch=="arm"', {
-              'include_dirs+': [
-                '../../src/arm',
-              ],
               'sources': [
                 '../../src/arm/assembler-arm-inl.h',
                 '../../src/arm/assembler-arm.cc',
@@ -702,19 +510,8 @@
                 '../../src/arm/simulator-arm.cc',
                 '../../src/arm/stub-cache-arm.cc',
               ],
-              'conditions': [
-                # The ARM assembler assumes the host is 32 bits,
-                # so force building 32-bit host tools.
-                ['host_arch=="x64" and _toolset=="host"', {
-                  'cflags': ['-m32'],
-                  'ldflags': ['-m32'],
-                }]
-              ]
             }],
             ['v8_target_arch=="ia32" or v8_target_arch=="mac" or OS=="mac"', {
-              'include_dirs+': [
-                '../../src/ia32',
-              ],
               'sources': [
                 '../../src/ia32/assembler-ia32-inl.h',
                 '../../src/ia32/assembler-ia32.cc',
@@ -746,9 +543,6 @@
               ],
             }],
             ['v8_target_arch=="x64" or v8_target_arch=="mac" or OS=="mac"', {
-              'include_dirs+': [
-                '../../src/x64',
-              ],
               'sources': [
                 '../../src/x64/assembler-x64-inl.h',
                 '../../src/x64/assembler-x64.cc',
@@ -781,10 +575,6 @@
             }],
             ['OS=="linux"', {
                 'link_settings': {
-                  'libraries': [
-                    # Needed for clock_gettime() used by src/platform-linux.cc.
-                    '-lrt',
-                  ],
                   'conditions': [
                     ['v8_compress_startup_data=="bz2"', {
                       'libraries': [
@@ -856,7 +646,7 @@
               ],
               'msvs_disabled_warnings': [4351, 4355, 4800],
               'link_settings':  {
-                'libraries': [ '-lwinmm.lib' ],
+                'libraries': [ '-lwinmm.lib', '-lws2_32.lib' ],
               },
             }],
             ['component=="shared_library"', {
@@ -870,7 +660,13 @@
         {
           'target_name': 'js2c',
           'type': 'none',
-          'toolsets': ['host'],
+          'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host'],
+            }, {
+              'toolsets': ['target'],
+            }],
+          ],
           'variables': {
             'library_files': [
               '../../src/runtime.js',
@@ -890,8 +686,9 @@
               '../../src/macros.py',
             ],
             'experimental_library_files': [
-              '../../src/proxy.js',
               '../../src/macros.py',
+              '../../src/proxy.js',
+              '../../src/weakmap.js',
             ],
           },
           'actions': [
@@ -936,7 +733,6 @@
         {
           'target_name': 'mksnapshot',
           'type': 'executable',
-          'toolsets': ['host'],
           'dependencies': [
             'v8_nosnapshot',
           ],
@@ -947,22 +743,21 @@
             '../../src/mksnapshot.cc',
           ],
           'conditions': [
-            # The ARM assembler assumes the host is 32 bits, so force building
-            # 32-bit host tools.
-            ['v8_target_arch=="arm" and host_arch=="x64" and _toolset=="host"', {
-              'cflags': ['-m32'],
-              'ldflags': ['-m32'],
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host'],
+            }, {
+              'toolsets': ['target'],
             }],
             ['v8_compress_startup_data=="bz2"', {
               'libraries': [
                 '-lbz2',
-              ]}],
-          ]
+              ]}
+            ],
+          ],
         },
         {
           'target_name': 'v8_shell',
           'type': 'executable',
-          'toolsets': ['host'],
           'dependencies': [
             'v8'
           ],
@@ -970,29 +765,56 @@
             '../../samples/shell.cc',
           ],
           'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host'],
+            }, {
+              'toolsets': ['target'],
+            }],
             ['OS=="win"', {
               # This could be gotten by not setting chromium_code, if that's OK.
               'defines': ['_CRT_SECURE_NO_WARNINGS'],
             }],
-            # The ARM assembler assumes the host is 32 bits, so force building
-            # 32-bit host tools.
-            ['v8_target_arch=="arm" and host_arch=="x64" and _toolset=="host"', {
-              'cflags': ['-m32'],
-              'ldflags': ['-m32'],
-            }],
             ['v8_compress_startup_data=="bz2"', {
               'libraries': [
                 '-lbz2',
               ]}],
           ],
         },
+        {
+          'target_name': 'preparser_lib',
+          'type': '<(library)',
+          'include_dirs+': [
+            '../../src',
+          ],
+          'sources': [
+            '../../src/allocation.cc',
+            '../../src/bignum.cc',
+            '../../src/cached-powers.cc',
+            '../../src/conversions.cc',
+            '../../src/hashmap.cc',
+            '../../src/preparse-data.cc',
+            '../../src/preparser.cc',
+            '../../src/preparser-api.cc',
+            '../../src/scanner-base.cc',
+            '../../src/strtod.cc',
+            '../../src/token.cc',
+            '../../src/unicode.cc',
+            '../../src/utils.cc',
+          ],
+        },
       ],
     }, { # use_system_v8 != 0
       'targets': [
         {
           'target_name': 'v8',
           'type': 'settings',
-          'toolsets': ['host', 'target'],
+          'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host', 'target'],
+            }, {
+              'toolsets': ['target'],
+            }],
+          ],
           'link_settings': {
             'libraries': [
               '-lv8',
@@ -1002,7 +824,13 @@
         {
           'target_name': 'v8_shell',
           'type': 'none',
-          'toolsets': ['host'],
+          'conditions': [
+            ['want_separate_host_toolset==1', {
+              'toolsets': ['host'],
+            }, {
+              'toolsets': ['target'],
+            }],
+          ],
           'dependencies': [
             'v8'
           ],
diff --git a/tools/oom_dump/README b/tools/oom_dump/README
index 0be7511..1d840b9 100644
--- a/tools/oom_dump/README
+++ b/tools/oom_dump/README
@@ -16,7 +16,9 @@
 
 Next step is to build v8.  Note: you should build x64 version of v8,
 if you're on 64-bit platform, otherwise you would get a link error when
-building oom_dump.
+building oom_dump.  Also, if you are testing against an older version of chrome
+you should build the corresponding version of V8 to make sure that the type-id 
+enum have the correct values.
 
 The last step is to build oom_dump itself.  The following command should work:
 
diff --git a/tools/presubmit.py b/tools/presubmit.py
index 1d80f92..c191fc7 100755
--- a/tools/presubmit.py
+++ b/tools/presubmit.py
@@ -248,12 +248,19 @@
   def IgnoreDir(self, name):
     return (super(SourceProcessor, self).IgnoreDir(name)
               or (name == 'third_party')
+              or (name == 'gyp')
+              or (name == 'out')
               or (name == 'obj'))
 
-  IGNORE_COPYRIGHTS = ['earley-boyer.js', 'raytrace.js', 'crypto.js',
-      'libraries.cc', 'libraries-empty.cc', 'jsmin.py', 'regexp-pcre.js']
-  IGNORE_TABS = IGNORE_COPYRIGHTS + ['unicode-test.js',
-      'html-comments.js']
+  IGNORE_COPYRIGHTS = ['cpplint.py',
+                       'earley-boyer.js',
+                       'raytrace.js',
+                       'crypto.js',
+                       'libraries.cc',
+                       'libraries-empty.cc',
+                       'jsmin.py',
+                       'regexp-pcre.js']
+  IGNORE_TABS = IGNORE_COPYRIGHTS + ['unicode-test.js', 'html-comments.js']
 
   def ProcessContents(self, name, contents):
     result = True
diff --git a/tools/test-wrapper-gypbuild.py b/tools/test-wrapper-gypbuild.py
new file mode 100755
index 0000000..9bc6bf6
--- /dev/null
+++ b/tools/test-wrapper-gypbuild.py
@@ -0,0 +1,227 @@
+#!/usr/bin/env python
+#
+# Copyright 2011 the V8 project authors. All rights reserved.
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+#     * Neither the name of Google Inc. nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+# This is a convenience script to run the existing tools/test.py script
+# when using the gyp/make based build.
+# It is intended as a stop-gap rather than a long-term solution.
+
+
+import optparse
+import os
+from os.path import join, dirname, abspath
+import subprocess
+import sys
+
+
+PROGRESS_INDICATORS = ['verbose', 'dots', 'color', 'mono']
+
+
+def BuildOptions():
+  result = optparse.OptionParser()
+
+  # Flags specific to this wrapper script:
+  result.add_option("--arch-and-mode",
+                    help='Architecture and mode in the format "arch.mode"',
+                    default=None)
+  result.add_option("--outdir",
+                    help='Base output directory',
+                    default='out')
+
+  # Flags this wrapper script handles itself:
+  result.add_option("-m", "--mode",
+                    help="The test modes in which to run (comma-separated)",
+                    default='release,debug')
+  result.add_option("--arch",
+                    help='The architectures to run tests for (comma-separated)',
+                    default='ia32,x64,arm')
+
+  # Flags that are passed on to the wrapped test.py script:
+  result.add_option("-v", "--verbose", help="Verbose output",
+      default=False, action="store_true")
+  result.add_option("-p", "--progress",
+      help="The style of progress indicator (verbose, dots, color, mono)",
+      choices=PROGRESS_INDICATORS, default="mono")
+  result.add_option("--report", help="Print a summary of the tests to be run",
+      default=False, action="store_true")
+  result.add_option("-s", "--suite", help="A test suite",
+      default=[], action="append")
+  result.add_option("-t", "--timeout", help="Timeout in seconds",
+      default=60, type="int")
+  result.add_option("--snapshot", help="Run the tests with snapshot turned on",
+      default=False, action="store_true")
+  result.add_option("--special-command", default=None)
+  result.add_option("--valgrind", help="Run tests through valgrind",
+      default=False, action="store_true")
+  result.add_option("--cat", help="Print the source of the tests",
+      default=False, action="store_true")
+  result.add_option("--warn-unused", help="Report unused rules",
+      default=False, action="store_true")
+  result.add_option("-j", help="The number of parallel tasks to run",
+      default=1, type="int")
+  result.add_option("--time", help="Print timing information after running",
+      default=False, action="store_true")
+  result.add_option("--suppress-dialogs", help="Suppress Windows dialogs for crashing tests",
+        dest="suppress_dialogs", default=True, action="store_true")
+  result.add_option("--no-suppress-dialogs", help="Display Windows dialogs for crashing tests",
+        dest="suppress_dialogs", action="store_false")
+  result.add_option("--isolates", help="Whether to test isolates", default=False, action="store_true")
+  result.add_option("--store-unexpected-output",
+      help="Store the temporary JS files from tests that fails",
+      dest="store_unexpected_output", default=True, action="store_true")
+  result.add_option("--no-store-unexpected-output",
+      help="Deletes the temporary JS files from tests that fails",
+      dest="store_unexpected_output", action="store_false")
+  result.add_option("--stress-only",
+                    help="Only run tests with --always-opt --stress-opt",
+                    default=False, action="store_true")
+  result.add_option("--nostress",
+                    help="Don't run crankshaft --always-opt --stress-op test",
+                    default=False, action="store_true")
+  result.add_option("--crankshaft",
+                    help="Run with the --crankshaft flag",
+                    default=False, action="store_true")
+  result.add_option("--shard-count",
+                    help="Split testsuites into this number of shards",
+                    default=1, type="int")
+  result.add_option("--shard-run",
+                    help="Run this shard from the split up tests.",
+                    default=1, type="int")
+  result.add_option("--noprof", help="Disable profiling support",
+                    default=False)
+
+  # Flags present in the original test.py that are unsupported in this wrapper:
+  # -S [-> scons_flags] (we build with gyp/make, not scons)
+  # --no-build (always true)
+  # --build-only (always false)
+  # --build-system (always 'gyp')
+  # --simulator (always true if arch==arm, always false otherwise)
+  # --shell (automatically chosen depending on arch and mode)
+
+  return result
+
+
+def ProcessOptions(options):
+  if options.arch_and_mode != None and options.arch_and_mode != "":
+    tokens = options.arch_and_mode.split(".")
+    options.arch = tokens[0]
+    options.mode = tokens[1]
+  options.mode = options.mode.split(',')
+  for mode in options.mode:
+    if not mode in ['debug', 'release']:
+      print "Unknown mode %s" % mode
+      return False
+  options.arch = options.arch.split(',')
+  for arch in options.arch:
+    if not arch in ['ia32', 'x64', 'arm']:
+      print "Unknown architecture %s" % arch
+      return False
+
+  return True
+
+
+def PassOnOptions(options):
+  result = []
+  if options.verbose:
+    result += ['--verbose']
+  if options.progress != 'mono':
+    result += ['--progress=' + options.progress]
+  if options.report:
+    result += ['--report']
+  if options.suite != []:
+    for suite in options.suite:
+      result += ['--suite=../../test/' + suite]
+  if options.timeout != 60:
+    result += ['--timeout=%s' % options.timeout]
+  if options.snapshot:
+    result += ['--snapshot']
+  if options.special_command:
+    result += ['--special-command=' + options.special_command]
+  if options.valgrind:
+    result += ['--valgrind']
+  if options.cat:
+    result += ['--cat']
+  if options.warn_unused:
+    result += ['--warn-unused']
+  if options.j != 1:
+    result += ['-j%s' % options.j]
+  if options.time:
+    result += ['--time']
+  if not options.suppress_dialogs:
+    result += ['--no-suppress-dialogs']
+  if options.isolates:
+    result += ['--isolates']
+  if not options.store_unexpected_output:
+    result += ['--no-store-unexpected_output']
+  if options.stress_only:
+    result += ['--stress-only']
+  if options.nostress:
+    result += ['--nostress']
+  if options.crankshaft:
+    result += ['--crankshaft']
+  if options.shard_count != 1:
+    result += ['--shard_count=%s' % options.shard_count]
+  if options.shard_run != 1:
+    result += ['--shard_run=%s' % options.shard_run]
+  if options.noprof:
+    result += ['--noprof']
+  return result
+
+
+def Main():
+  parser = BuildOptions()
+  (options, args) = parser.parse_args()
+  if not ProcessOptions(options):
+    parser.print_help()
+    return 1
+
+  workspace = abspath(join(dirname(sys.argv[0]), '..'))
+  args_for_children = [workspace + '/tools/test.py'] + PassOnOptions(options)
+  args_for_children += ['--no-build', '--build-system=gyp']
+  for arg in args:
+    args_for_children += [arg]
+  returncodes = 0
+
+  for mode in options.mode:
+    for arch in options.arch:
+      print ">>> running tests for %s.%s" % (arch, mode)
+      shell = workspace + '/' + options.outdir + '/' + arch + '.' + mode + "/d8"
+      child = subprocess.Popen(' '.join(args_for_children +
+                                        ['--arch=' + arch] +
+                                        ['--mode=' + mode] +
+                                        ['--shell=' + shell]),
+                               shell=True,
+                               cwd=workspace)
+      returncodes += child.wait()
+
+  return returncodes
+
+
+if __name__ == '__main__':
+  sys.exit(Main())
diff --git a/tools/test.py b/tools/test.py
index ec21ffe..d40159c 100755
--- a/tools/test.py
+++ b/tools/test.py
@@ -1181,6 +1181,8 @@
       default=False, action="store_true")
   result.add_option("--build-only", help="Only build requirements, don't run the tests",
       default=False, action="store_true")
+  result.add_option("--build-system", help="Build system in use (scons or gyp)",
+      default='scons')
   result.add_option("--report", help="Print a summary of the tests to be run",
       default=False, action="store_true")
   result.add_option("-s", "--suite", help="A test suite",
@@ -1208,7 +1210,7 @@
         dest="suppress_dialogs", default=True, action="store_true")
   result.add_option("--no-suppress-dialogs", help="Display Windows dialogs for crashing tests",
         dest="suppress_dialogs", action="store_false")
-  result.add_option("--shell", help="Path to V8 shell", default="shell")
+  result.add_option("--shell", help="Path to V8 shell", default="d8")
   result.add_option("--isolates", help="Whether to test isolates", default=False, action="store_true")
   result.add_option("--store-unexpected-output",
       help="Store the temporary JS files from tests that fails",
@@ -1271,21 +1273,30 @@
     if options.special_command:
       options.special_command += " --crankshaft"
     else:
-      options.special_command = "@--crankshaft"
-  if options.shell == "d8":
+      options.special_command = "@ --crankshaft"
+  if options.shell.endswith("d8"):
     if options.special_command:
       options.special_command += " --test"
     else:
-      options.special_command = "@--test"
+      options.special_command = "@ --test"
   if options.noprof:
     options.scons_flags.append("prof=off")
     options.scons_flags.append("profilingsupport=off")
+  if options.build_system == 'gyp':
+    if options.build_only:
+      print "--build-only not supported for gyp, please build manually."
+      options.build_only = False
   return True
 
 
+def DoSkip(case):
+  return (SKIP in case.outcomes) or (SLOW in case.outcomes)
+
+
 REPORT_TEMPLATE = """\
 Total: %(total)i tests
  * %(skipped)4d tests will be skipped
+ * %(timeout)4d tests are expected to timeout sometimes
  * %(nocrash)4d tests are expected to be flaky but not crash
  * %(pass)4d tests are expected to pass
  * %(fail_ok)4d tests are expected to fail that we won't fix
@@ -1297,10 +1308,11 @@
     return (PASS in o) and (FAIL in o) and (not CRASH in o) and (not OKAY in o)
   def IsFailOk(o):
     return (len(o) == 2) and (FAIL in o) and (OKAY in o)
-  unskipped = [c for c in cases if not SKIP in c.outcomes]
+  unskipped = [c for c in cases if not DoSkip(c)]
   print REPORT_TEMPLATE % {
     'total': len(cases),
     'skipped': len(cases) - len(unskipped),
+    'timeout': len([t for t in unskipped if TIMEOUT in t.outcomes]),
     'nocrash': len([t for t in unskipped if IsFlaky(t.outcomes)]),
     'pass': len([t for t in unskipped if list(t.outcomes) == [PASS]]),
     'fail_ok': len([t for t in unskipped if IsFailOk(t.outcomes)]),
@@ -1399,6 +1411,9 @@
     run_valgrind = join(workspace, "tools", "run-valgrind.py")
     options.special_command = "python -u " + run_valgrind + " @"
 
+  if options.build_system == 'gyp':
+    SUFFIX['debug'] = ''
+
   shell = abspath(options.shell)
   buildspace = dirname(shell)
 
@@ -1472,15 +1487,14 @@
     for rule in globally_unused_rules:
       print "Rule for '%s' was not used." % '/'.join([str(s) for s in rule.path])
 
+  if not options.isolates:
+    all_cases = [c for c in all_cases if not c.TestsIsolates()]
+
   if options.report:
     PrintReport(all_cases)
 
   result = None
-  def DoSkip(case):
-    return SKIP in case.outcomes or SLOW in case.outcomes
   cases_to_run = [ c for c in all_cases if not DoSkip(c) ]
-  if not options.isolates:
-    cases_to_run = [c for c in cases_to_run if not c.TestsIsolates()]
   if len(cases_to_run) == 0:
     print "No tests to run."
     return 0