src/safepoint-table.h - platform/external/v8 - Git at Google

 // 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_SAFEPOINT_TABLE_H_
 #define V8_SAFEPOINT_TABLE_H_

 #include "heap.h"
 #include "v8memory.h"
 #include "zone.h"

 namespace v8 {
 namespace internal {

 struct Register;

 class SafepointEntry BASE_EMBEDDED {
  public:
   SafepointEntry() : info_(0), bits_(NULL) {}

   SafepointEntry(unsigned info, uint8_t* bits) : info_(info), bits_(bits) {
     ASSERT(is_valid());
   }

   bool is_valid() const { return bits_ != NULL; }

   bool Equals(const SafepointEntry& other) const {
     return info_ == other.info_ && bits_ == other.bits_;
   }

   void Reset() {
     info_ = 0;
     bits_ = NULL;
   }

   int deoptimization_index() const {
     ASSERT(is_valid());
     return DeoptimizationIndexField::decode(info_);
   }

   int gap_code_size() const {
     ASSERT(is_valid());
     return GapCodeSizeField::decode(info_);
   }

   int argument_count() const {
     ASSERT(is_valid());
     return ArgumentsField::decode(info_);
   }

   bool has_doubles() const {
     ASSERT(is_valid());
     return SaveDoublesField::decode(info_);
   }

   uint8_t* bits() {
     ASSERT(is_valid());
     return bits_;
   }

   bool HasRegisters() const;
   bool HasRegisterAt(int reg_index) const;

   // Reserve 13 bits for the gap code size. On ARM a constant pool can be
   // emitted when generating the gap code. The size of the const pool is less
   // than what can be represented in 12 bits, so 13 bits gives room for having
   // instructions before potentially emitting a constant pool.
   static const int kGapCodeSizeBits = 13;
   static const int kArgumentsFieldBits = 3;
   static const int kSaveDoublesFieldBits = 1;
   static const int kDeoptIndexBits =
       32 - kGapCodeSizeBits - kArgumentsFieldBits - kSaveDoublesFieldBits;
   class GapCodeSizeField: public BitField<unsigned, 0, kGapCodeSizeBits> {};
   class DeoptimizationIndexField: public BitField<int,
                                                   kGapCodeSizeBits,
                                                   kDeoptIndexBits> {};  // NOLINT
   class ArgumentsField: public BitField<unsigned,
                                         kGapCodeSizeBits + kDeoptIndexBits,
                                         kArgumentsFieldBits> {};  // NOLINT
   class SaveDoublesField: public BitField<bool,
                                           kGapCodeSizeBits + kDeoptIndexBits +
                                           kArgumentsFieldBits,
                                           kSaveDoublesFieldBits> { }; // NOLINT

  private:
   unsigned info_;
   uint8_t* bits_;
 };


 class SafepointTable BASE_EMBEDDED {
  public:
   explicit SafepointTable(Code* code);

   int size() const {
     return kHeaderSize +
            (length_ * (kPcAndDeoptimizationIndexSize + entry_size_)); }
   unsigned length() const { return length_; }
   unsigned entry_size() const { return entry_size_; }

   unsigned GetPcOffset(unsigned index) const {
     ASSERT(index < length_);
     return Memory::uint32_at(GetPcOffsetLocation(index));
   }

   SafepointEntry GetEntry(unsigned index) const {
     ASSERT(index < length_);
     unsigned info = Memory::uint32_at(GetInfoLocation(index));
     uint8_t* bits = &Memory::uint8_at(entries_ + (index * entry_size_));
     return SafepointEntry(info, bits);
   }

   // Returns the entry for the given pc.
   SafepointEntry FindEntry(Address pc) const;

   void PrintEntry(unsigned index) const;

  private:
   static const uint8_t kNoRegisters = 0xFF;

   static const int kLengthOffset = 0;
   static const int kEntrySizeOffset = kLengthOffset + kIntSize;
   static const int kHeaderSize = kEntrySizeOffset + kIntSize;

   static const int kPcSize = kIntSize;
   static const int kDeoptimizationIndexSize = kIntSize;
   static const int kPcAndDeoptimizationIndexSize =
       kPcSize + kDeoptimizationIndexSize;

   Address GetPcOffsetLocation(unsigned index) const {
     return pc_and_deoptimization_indexes_ +
            (index * kPcAndDeoptimizationIndexSize);
   }

   Address GetInfoLocation(unsigned index) const {
     return GetPcOffsetLocation(index) + kPcSize;
   }

   static void PrintBits(uint8_t byte, int digits);

   AssertNoAllocation no_allocation_;
   Code* code_;
   unsigned length_;
   unsigned entry_size_;

   Address pc_and_deoptimization_indexes_;
   Address entries_;

   friend class SafepointTableBuilder;
   friend class SafepointEntry;

   DISALLOW_COPY_AND_ASSIGN(SafepointTable);
 };


 class Safepoint BASE_EMBEDDED {
  public:
   typedef enum {
     kSimple = 0,
     kWithRegisters = 1 << 0,
     kWithDoubles = 1 << 1,
     kWithRegistersAndDoubles = kWithRegisters | kWithDoubles
   } Kind;

   static const int kNoDeoptimizationIndex =
       (1 << (SafepointEntry::kDeoptIndexBits)) - 1;

   void DefinePointerSlot(int index) { indexes_->Add(index); }
   void DefinePointerRegister(Register reg);

  private:
   Safepoint(ZoneList<int>* indexes, ZoneList<int>* registers) :
       indexes_(indexes), registers_(registers) { }
   ZoneList<int>* indexes_;
   ZoneList<int>* registers_;

   friend class SafepointTableBuilder;
 };


 class SafepointTableBuilder BASE_EMBEDDED {
  public:
   SafepointTableBuilder()
       : deoptimization_info_(32),
         indexes_(32),
         registers_(32),
         emitted_(false) { }

   // Get the offset of the emitted safepoint table in the code.
   unsigned GetCodeOffset() const;

   // Define a new safepoint for the current position in the body.
   Safepoint DefineSafepoint(Assembler* assembler,
                             Safepoint::Kind kind,
                             int arguments,
                             int deoptimization_index);

   // Update the last safepoint with the size of the code generated until the
   // end of the gap following it.
   void SetPcAfterGap(int pc) {
     ASSERT(!deoptimization_info_.is_empty());
     int index = deoptimization_info_.length() - 1;
     deoptimization_info_[index].pc_after_gap = pc;
   }

   // Get the end pc offset of the last safepoint, including the code generated
   // until the end of the gap following it.
   unsigned GetPcAfterGap() {
     int index = deoptimization_info_.length();
     if (index == 0) return 0;
     return deoptimization_info_[index - 1].pc_after_gap;
   }

   // Emit the safepoint table after the body. The number of bits per
   // entry must be enough to hold all the pointer indexes.
   void Emit(Assembler* assembler, int bits_per_entry);

   // Count the number of deoptimization points where the next
   // following deoptimization point comes less than limit bytes
   // after the end of this point's gap.
   int CountShortDeoptimizationIntervals(unsigned limit);

  private:
   struct DeoptimizationInfo {
     unsigned pc;
     unsigned deoptimization_index;
     unsigned pc_after_gap;
     unsigned arguments;
     bool has_doubles;
   };

   uint32_t EncodeExceptPC(const DeoptimizationInfo& info);

   ZoneList<DeoptimizationInfo> deoptimization_info_;
   ZoneList<ZoneList<int>*> indexes_;
   ZoneList<ZoneList<int>*> registers_;

   unsigned offset_;
   bool emitted_;

   DISALLOW_COPY_AND_ASSIGN(SafepointTableBuilder);
 };

 } }  // namespace v8::internal

 #endif  // V8_SAFEPOINT_TABLE_H_
	// 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_SAFEPOINT_TABLE_H_
	#define V8_SAFEPOINT_TABLE_H_

	#include "heap.h"
	#include "v8memory.h"
	#include "zone.h"

	namespace v8 {
	namespace internal {

	struct Register;

	class SafepointEntry BASE_EMBEDDED {
	public:
	SafepointEntry() : info_(0), bits_(NULL) {}

	SafepointEntry(unsigned info, uint8_t* bits) : info_(info), bits_(bits) {
	ASSERT(is_valid());
	}

	bool is_valid() const { return bits_ != NULL; }

	bool Equals(const SafepointEntry& other) const {
	return info_ == other.info_ && bits_ == other.bits_;
	}

	void Reset() {
	info_ = 0;
	bits_ = NULL;
	}

	int deoptimization_index() const {
	ASSERT(is_valid());
	return DeoptimizationIndexField::decode(info_);
	}

	int gap_code_size() const {
	ASSERT(is_valid());
	return GapCodeSizeField::decode(info_);
	}

	int argument_count() const {
	ASSERT(is_valid());
	return ArgumentsField::decode(info_);
	}

	bool has_doubles() const {
	ASSERT(is_valid());
	return SaveDoublesField::decode(info_);
	}

	uint8_t* bits() {
	ASSERT(is_valid());
	return bits_;
	}

	bool HasRegisters() const;
	bool HasRegisterAt(int reg_index) const;

	// Reserve 13 bits for the gap code size. On ARM a constant pool can be
	// emitted when generating the gap code. The size of the const pool is less
	// than what can be represented in 12 bits, so 13 bits gives room for having
	// instructions before potentially emitting a constant pool.
	static const int kGapCodeSizeBits = 13;
	static const int kArgumentsFieldBits = 3;
	static const int kSaveDoublesFieldBits = 1;
	static const int kDeoptIndexBits =
	32 - kGapCodeSizeBits - kArgumentsFieldBits - kSaveDoublesFieldBits;
	class GapCodeSizeField: public BitField<unsigned, 0, kGapCodeSizeBits> {};
	class DeoptimizationIndexField: public BitField<int,
	kGapCodeSizeBits,
	kDeoptIndexBits> {}; // NOLINT
	class ArgumentsField: public BitField<unsigned,
	kGapCodeSizeBits + kDeoptIndexBits,
	kArgumentsFieldBits> {}; // NOLINT
	class SaveDoublesField: public BitField<bool,
	kGapCodeSizeBits + kDeoptIndexBits +
	kArgumentsFieldBits,
	kSaveDoublesFieldBits> { }; // NOLINT

	private:
	unsigned info_;
	uint8_t* bits_;
	};


	class SafepointTable BASE_EMBEDDED {
	public:
	explicit SafepointTable(Code* code);

	int size() const {
	return kHeaderSize +
	(length_ * (kPcAndDeoptimizationIndexSize + entry_size_)); }
	unsigned length() const { return length_; }
	unsigned entry_size() const { return entry_size_; }

	unsigned GetPcOffset(unsigned index) const {
	ASSERT(index < length_);
	return Memory::uint32_at(GetPcOffsetLocation(index));
	}

	SafepointEntry GetEntry(unsigned index) const {
	ASSERT(index < length_);
	unsigned info = Memory::uint32_at(GetInfoLocation(index));
	uint8_t* bits = &Memory::uint8_at(entries_ + (index * entry_size_));
	return SafepointEntry(info, bits);
	}

	// Returns the entry for the given pc.
	SafepointEntry FindEntry(Address pc) const;

	void PrintEntry(unsigned index) const;

	private:
	static const uint8_t kNoRegisters = 0xFF;

	static const int kLengthOffset = 0;
	static const int kEntrySizeOffset = kLengthOffset + kIntSize;
	static const int kHeaderSize = kEntrySizeOffset + kIntSize;

	static const int kPcSize = kIntSize;
	static const int kDeoptimizationIndexSize = kIntSize;
	static const int kPcAndDeoptimizationIndexSize =
	kPcSize + kDeoptimizationIndexSize;

	Address GetPcOffsetLocation(unsigned index) const {
	return pc_and_deoptimization_indexes_ +
	(index * kPcAndDeoptimizationIndexSize);
	}

	Address GetInfoLocation(unsigned index) const {
	return GetPcOffsetLocation(index) + kPcSize;
	}

	static void PrintBits(uint8_t byte, int digits);

	AssertNoAllocation no_allocation_;
	Code* code_;
	unsigned length_;
	unsigned entry_size_;

	Address pc_and_deoptimization_indexes_;
	Address entries_;

	friend class SafepointTableBuilder;
	friend class SafepointEntry;

	DISALLOW_COPY_AND_ASSIGN(SafepointTable);
	};


	class Safepoint BASE_EMBEDDED {
	public:
	typedef enum {
	kSimple = 0,
	kWithRegisters = 1 << 0,
	kWithDoubles = 1 << 1,
	kWithRegistersAndDoubles = kWithRegisters \| kWithDoubles
	} Kind;

	static const int kNoDeoptimizationIndex =
	(1 << (SafepointEntry::kDeoptIndexBits)) - 1;

	void DefinePointerSlot(int index) { indexes_->Add(index); }
	void DefinePointerRegister(Register reg);

	private:
	Safepoint(ZoneList<int>* indexes, ZoneList<int>* registers) :
	indexes_(indexes), registers_(registers) { }
	ZoneList<int>* indexes_;
	ZoneList<int>* registers_;

	friend class SafepointTableBuilder;
	};


	class SafepointTableBuilder BASE_EMBEDDED {
	public:
	SafepointTableBuilder()
	: deoptimization_info_(32),
	indexes_(32),
	registers_(32),
	emitted_(false) { }

	// Get the offset of the emitted safepoint table in the code.
	unsigned GetCodeOffset() const;

	// Define a new safepoint for the current position in the body.
	Safepoint DefineSafepoint(Assembler* assembler,
	Safepoint::Kind kind,
	int arguments,
	int deoptimization_index);

	// Update the last safepoint with the size of the code generated until the
	// end of the gap following it.
	void SetPcAfterGap(int pc) {
	ASSERT(!deoptimization_info_.is_empty());
	int index = deoptimization_info_.length() - 1;
	deoptimization_info_[index].pc_after_gap = pc;
	}

	// Get the end pc offset of the last safepoint, including the code generated
	// until the end of the gap following it.
	unsigned GetPcAfterGap() {
	int index = deoptimization_info_.length();
	if (index == 0) return 0;
	return deoptimization_info_[index - 1].pc_after_gap;
	}

	// Emit the safepoint table after the body. The number of bits per
	// entry must be enough to hold all the pointer indexes.
	void Emit(Assembler* assembler, int bits_per_entry);

	// Count the number of deoptimization points where the next
	// following deoptimization point comes less than limit bytes
	// after the end of this point's gap.
	int CountShortDeoptimizationIntervals(unsigned limit);

	private:
	struct DeoptimizationInfo {
	unsigned pc;
	unsigned deoptimization_index;
	unsigned pc_after_gap;
	unsigned arguments;
	bool has_doubles;
	};

	uint32_t EncodeExceptPC(const DeoptimizationInfo& info);

	ZoneList<DeoptimizationInfo> deoptimization_info_;
	ZoneList<ZoneList<int>*> indexes_;
	ZoneList<ZoneList<int>*> registers_;

	unsigned offset_;
	bool emitted_;

	DISALLOW_COPY_AND_ASSIGN(SafepointTableBuilder);
	};

	} } // namespace v8::internal

	#endif // V8_SAFEPOINT_TABLE_H_