src/arm/lithium-gap-resolver-arm.cc - platform/external/v8 - Git at Google

 // Copyright 2012 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 "arm/lithium-gap-resolver-arm.h"
 #include "arm/lithium-codegen-arm.h"

 namespace v8 {
 namespace internal {

 static const Register kSavedValueRegister = { 9 };

 LGapResolver::LGapResolver(LCodeGen* owner)
     : cgen_(owner), moves_(32), root_index_(0), in_cycle_(false),
       saved_destination_(NULL) { }


 void LGapResolver::Resolve(LParallelMove* parallel_move) {
   ASSERT(moves_.is_empty());
   // Build up a worklist of moves.
   BuildInitialMoveList(parallel_move);

   for (int i = 0; i < moves_.length(); ++i) {
     LMoveOperands move = moves_[i];
     // Skip constants to perform them last.  They don't block other moves
     // and skipping such moves with register destinations keeps those
     // registers free for the whole algorithm.
     if (!move.IsEliminated() && !move.source()->IsConstantOperand()) {
       root_index_ = i;  // Any cycle is found when by reaching this move again.
       PerformMove(i);
       if (in_cycle_) {
         RestoreValue();
       }
     }
   }

   // Perform the moves with constant sources.
   for (int i = 0; i < moves_.length(); ++i) {
     if (!moves_[i].IsEliminated()) {
       ASSERT(moves_[i].source()->IsConstantOperand());
       EmitMove(i);
     }
   }

   moves_.Rewind(0);
 }


 void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) {
   // Perform a linear sweep of the moves to add them to the initial list of
   // moves to perform, ignoring any move that is redundant (the source is
   // the same as the destination, the destination is ignored and
   // unallocated, or the move was already eliminated).
   const ZoneList<LMoveOperands>* moves = parallel_move->move_operands();
   for (int i = 0; i < moves->length(); ++i) {
     LMoveOperands move = moves->at(i);
     if (!move.IsRedundant()) moves_.Add(move);
   }
   Verify();
 }


 void LGapResolver::PerformMove(int index) {
   // Each call to this function performs a move and deletes it from the move
   // graph.  We first recursively perform any move blocking this one.  We
   // mark a move as "pending" on entry to PerformMove in order to detect
   // cycles in the move graph.

   // We can only find a cycle, when doing a depth-first traversal of moves,
   // be encountering the starting move again. So by spilling the source of
   // the starting move, we break the cycle.  All moves are then unblocked,
   // and the starting move is completed by writing the spilled value to
   // its destination.  All other moves from the spilled source have been
   // completed prior to breaking the cycle.
   // An additional complication is that moves to MemOperands with large
   // offsets (more than 1K or 4K) require us to spill this spilled value to
   // the stack, to free up the register.
   ASSERT(!moves_[index].IsPending());
   ASSERT(!moves_[index].IsRedundant());

   // Clear this move's destination to indicate a pending move.  The actual
   // destination is saved in a stack allocated local.  Multiple moves can
   // be pending because this function is recursive.
   ASSERT(moves_[index].source() != NULL);  // Or else it will look eliminated.
   LOperand* destination = moves_[index].destination();
   moves_[index].set_destination(NULL);

   // Perform a depth-first traversal of the move graph to resolve
   // dependencies.  Any unperformed, unpending move with a source the same
   // as this one's destination blocks this one so recursively perform all
   // such moves.
   for (int i = 0; i < moves_.length(); ++i) {
     LMoveOperands other_move = moves_[i];
     if (other_move.Blocks(destination) && !other_move.IsPending()) {
       PerformMove(i);
       // If there is a blocking, pending move it must be moves_[root_index_]
       // and all other moves with the same source as moves_[root_index_] are
       // sucessfully executed (because they are cycle-free) by this loop.
     }
   }

   // We are about to resolve this move and don't need it marked as
   // pending, so restore its destination.
   moves_[index].set_destination(destination);

   // The move may be blocked on a pending move, which must be the starting move.
   // In this case, we have a cycle, and we save the source of this move to
   // a scratch register to break it.
   LMoveOperands other_move = moves_[root_index_];
   if (other_move.Blocks(destination)) {
     ASSERT(other_move.IsPending());
     BreakCycle(index);
     return;
   }

   // This move is no longer blocked.
   EmitMove(index);
 }


 void LGapResolver::Verify() {
 #ifdef ENABLE_SLOW_ASSERTS
   // No operand should be the destination for more than one move.
   for (int i = 0; i < moves_.length(); ++i) {
     LOperand* destination = moves_[i].destination();
     for (int j = i + 1; j < moves_.length(); ++j) {
       SLOW_ASSERT(!destination->Equals(moves_[j].destination()));
     }
   }
 #endif
 }

 #define __ ACCESS_MASM(cgen_->masm())

 void LGapResolver::BreakCycle(int index) {
   // We save in a register the value that should end up in the source of
   // moves_[root_index].  After performing all moves in the tree rooted
   // in that move, we save the value to that source.
   ASSERT(moves_[index].destination()->Equals(moves_[root_index_].source()));
   ASSERT(!in_cycle_);
   in_cycle_ = true;
   LOperand* source = moves_[index].source();
   saved_destination_ = moves_[index].destination();
   if (source->IsRegister()) {
     __ mov(kSavedValueRegister, cgen_->ToRegister(source));
   } else if (source->IsStackSlot()) {
     __ ldr(kSavedValueRegister, cgen_->ToMemOperand(source));
   } else if (source->IsDoubleRegister()) {
     __ vmov(kScratchDoubleReg, cgen_->ToDoubleRegister(source));
   } else if (source->IsDoubleStackSlot()) {
     __ vldr(kScratchDoubleReg, cgen_->ToMemOperand(source));
   } else {
     UNREACHABLE();
   }
   // This move will be done by restoring the saved value to the destination.
   moves_[index].Eliminate();
 }


 void LGapResolver::RestoreValue() {
   ASSERT(in_cycle_);
   ASSERT(saved_destination_ != NULL);

   // Spilled value is in kSavedValueRegister or kSavedDoubleValueRegister.
   if (saved_destination_->IsRegister()) {
     __ mov(cgen_->ToRegister(saved_destination_), kSavedValueRegister);
   } else if (saved_destination_->IsStackSlot()) {
     __ str(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_));
   } else if (saved_destination_->IsDoubleRegister()) {
     __ vmov(cgen_->ToDoubleRegister(saved_destination_), kScratchDoubleReg);
   } else if (saved_destination_->IsDoubleStackSlot()) {
     __ vstr(kScratchDoubleReg, cgen_->ToMemOperand(saved_destination_));
   } else {
     UNREACHABLE();
   }

   in_cycle_ = false;
   saved_destination_ = NULL;
 }


 void LGapResolver::EmitMove(int index) {
   LOperand* source = moves_[index].source();
   LOperand* destination = moves_[index].destination();

   // Dispatch on the source and destination operand kinds.  Not all
   // combinations are possible.

   if (source->IsRegister()) {
     Register source_register = cgen_->ToRegister(source);
     if (destination->IsRegister()) {
       __ mov(cgen_->ToRegister(destination), source_register);
     } else {
       ASSERT(destination->IsStackSlot());
       __ str(source_register, cgen_->ToMemOperand(destination));
     }

   } else if (source->IsStackSlot()) {
     MemOperand source_operand = cgen_->ToMemOperand(source);
     if (destination->IsRegister()) {
       __ ldr(cgen_->ToRegister(destination), source_operand);
     } else {
       ASSERT(destination->IsStackSlot());
       MemOperand destination_operand = cgen_->ToMemOperand(destination);
       if (in_cycle_) {
         if (!destination_operand.OffsetIsUint12Encodable()) {
           // ip is overwritten while saving the value to the destination.
           // Therefore we can't use ip.  It is OK if the read from the source
           // destroys ip, since that happens before the value is read.
           __ vldr(kScratchDoubleReg.low(), source_operand);
           __ vstr(kScratchDoubleReg.low(), destination_operand);
         } else {
           __ ldr(ip, source_operand);
           __ str(ip, destination_operand);
         }
       } else {
         __ ldr(kSavedValueRegister, source_operand);
         __ str(kSavedValueRegister, destination_operand);
       }
     }

   } else if (source->IsConstantOperand()) {
     Operand source_operand = cgen_->ToOperand(source);
     if (destination->IsRegister()) {
       __ mov(cgen_->ToRegister(destination), source_operand);
     } else {
       ASSERT(destination->IsStackSlot());
       ASSERT(!in_cycle_);  // Constant moves happen after all cycles are gone.
       __ mov(kSavedValueRegister, source_operand);
       __ str(kSavedValueRegister, cgen_->ToMemOperand(destination));
     }

   } else if (source->IsDoubleRegister()) {
     DoubleRegister source_register = cgen_->ToDoubleRegister(source);
     if (destination->IsDoubleRegister()) {
       __ vmov(cgen_->ToDoubleRegister(destination), source_register);
     } else {
       ASSERT(destination->IsDoubleStackSlot());
       __ vstr(source_register, cgen_->ToMemOperand(destination));
     }

   } else if (source->IsDoubleStackSlot()) {
     MemOperand source_operand = cgen_->ToMemOperand(source);
     if (destination->IsDoubleRegister()) {
       __ vldr(cgen_->ToDoubleRegister(destination), source_operand);
     } else {
       ASSERT(destination->IsDoubleStackSlot());
       MemOperand destination_operand = cgen_->ToMemOperand(destination);
       if (in_cycle_) {
         // kSavedDoubleValueRegister was used to break the cycle,
         // but kSavedValueRegister is free.
         MemOperand source_high_operand =
             cgen_->ToHighMemOperand(source);
         MemOperand destination_high_operand =
             cgen_->ToHighMemOperand(destination);
         __ ldr(kSavedValueRegister, source_operand);
         __ str(kSavedValueRegister, destination_operand);
         __ ldr(kSavedValueRegister, source_high_operand);
         __ str(kSavedValueRegister, destination_high_operand);
       } else {
         __ vldr(kScratchDoubleReg, source_operand);
         __ vstr(kScratchDoubleReg, destination_operand);
       }
     }
   } else {
     UNREACHABLE();
   }

   moves_[index].Eliminate();
 }


 #undef __

 } }  // namespace v8::internal
	// Copyright 2012 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 "arm/lithium-gap-resolver-arm.h"
	#include "arm/lithium-codegen-arm.h"

	namespace v8 {
	namespace internal {

	static const Register kSavedValueRegister = { 9 };

	LGapResolver::LGapResolver(LCodeGen* owner)
	: cgen_(owner), moves_(32), root_index_(0), in_cycle_(false),
	saved_destination_(NULL) { }


	void LGapResolver::Resolve(LParallelMove* parallel_move) {
	ASSERT(moves_.is_empty());
	// Build up a worklist of moves.
	BuildInitialMoveList(parallel_move);

	for (int i = 0; i < moves_.length(); ++i) {
	LMoveOperands move = moves_[i];
	// Skip constants to perform them last. They don't block other moves
	// and skipping such moves with register destinations keeps those
	// registers free for the whole algorithm.
	if (!move.IsEliminated() && !move.source()->IsConstantOperand()) {
	root_index_ = i; // Any cycle is found when by reaching this move again.
	PerformMove(i);
	if (in_cycle_) {
	RestoreValue();
	}
	}
	}

	// Perform the moves with constant sources.
	for (int i = 0; i < moves_.length(); ++i) {
	if (!moves_[i].IsEliminated()) {
	ASSERT(moves_[i].source()->IsConstantOperand());
	EmitMove(i);
	}
	}

	moves_.Rewind(0);
	}


	void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) {
	// Perform a linear sweep of the moves to add them to the initial list of
	// moves to perform, ignoring any move that is redundant (the source is
	// the same as the destination, the destination is ignored and
	// unallocated, or the move was already eliminated).
	const ZoneList<LMoveOperands>* moves = parallel_move->move_operands();
	for (int i = 0; i < moves->length(); ++i) {
	LMoveOperands move = moves->at(i);
	if (!move.IsRedundant()) moves_.Add(move);
	}
	Verify();
	}


	void LGapResolver::PerformMove(int index) {
	// Each call to this function performs a move and deletes it from the move
	// graph. We first recursively perform any move blocking this one. We
	// mark a move as "pending" on entry to PerformMove in order to detect
	// cycles in the move graph.

	// We can only find a cycle, when doing a depth-first traversal of moves,
	// be encountering the starting move again. So by spilling the source of
	// the starting move, we break the cycle. All moves are then unblocked,
	// and the starting move is completed by writing the spilled value to
	// its destination. All other moves from the spilled source have been
	// completed prior to breaking the cycle.
	// An additional complication is that moves to MemOperands with large
	// offsets (more than 1K or 4K) require us to spill this spilled value to
	// the stack, to free up the register.
	ASSERT(!moves_[index].IsPending());
	ASSERT(!moves_[index].IsRedundant());

	// Clear this move's destination to indicate a pending move. The actual
	// destination is saved in a stack allocated local. Multiple moves can
	// be pending because this function is recursive.
	ASSERT(moves_[index].source() != NULL); // Or else it will look eliminated.
	LOperand* destination = moves_[index].destination();
	moves_[index].set_destination(NULL);

	// Perform a depth-first traversal of the move graph to resolve
	// dependencies. Any unperformed, unpending move with a source the same
	// as this one's destination blocks this one so recursively perform all
	// such moves.
	for (int i = 0; i < moves_.length(); ++i) {
	LMoveOperands other_move = moves_[i];
	if (other_move.Blocks(destination) && !other_move.IsPending()) {
	PerformMove(i);
	// If there is a blocking, pending move it must be moves_[root_index_]
	// and all other moves with the same source as moves_[root_index_] are
	// sucessfully executed (because they are cycle-free) by this loop.
	}
	}

	// We are about to resolve this move and don't need it marked as
	// pending, so restore its destination.
	moves_[index].set_destination(destination);

	// The move may be blocked on a pending move, which must be the starting move.
	// In this case, we have a cycle, and we save the source of this move to
	// a scratch register to break it.
	LMoveOperands other_move = moves_[root_index_];
	if (other_move.Blocks(destination)) {
	ASSERT(other_move.IsPending());
	BreakCycle(index);
	return;
	}

	// This move is no longer blocked.
	EmitMove(index);
	}


	void LGapResolver::Verify() {
	#ifdef ENABLE_SLOW_ASSERTS
	// No operand should be the destination for more than one move.
	for (int i = 0; i < moves_.length(); ++i) {
	LOperand* destination = moves_[i].destination();
	for (int j = i + 1; j < moves_.length(); ++j) {
	SLOW_ASSERT(!destination->Equals(moves_[j].destination()));
	}
	}
	#endif
	}

	#define __ ACCESS_MASM(cgen_->masm())

	void LGapResolver::BreakCycle(int index) {
	// We save in a register the value that should end up in the source of
	// moves_[root_index]. After performing all moves in the tree rooted
	// in that move, we save the value to that source.
	ASSERT(moves_[index].destination()->Equals(moves_[root_index_].source()));
	ASSERT(!in_cycle_);
	in_cycle_ = true;
	LOperand* source = moves_[index].source();
	saved_destination_ = moves_[index].destination();
	if (source->IsRegister()) {
	__ mov(kSavedValueRegister, cgen_->ToRegister(source));
	} else if (source->IsStackSlot()) {
	__ ldr(kSavedValueRegister, cgen_->ToMemOperand(source));
	} else if (source->IsDoubleRegister()) {
	__ vmov(kScratchDoubleReg, cgen_->ToDoubleRegister(source));
	} else if (source->IsDoubleStackSlot()) {
	__ vldr(kScratchDoubleReg, cgen_->ToMemOperand(source));
	} else {
	UNREACHABLE();
	}
	// This move will be done by restoring the saved value to the destination.
	moves_[index].Eliminate();
	}


	void LGapResolver::RestoreValue() {
	ASSERT(in_cycle_);
	ASSERT(saved_destination_ != NULL);

	// Spilled value is in kSavedValueRegister or kSavedDoubleValueRegister.
	if (saved_destination_->IsRegister()) {
	__ mov(cgen_->ToRegister(saved_destination_), kSavedValueRegister);
	} else if (saved_destination_->IsStackSlot()) {
	__ str(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_));
	} else if (saved_destination_->IsDoubleRegister()) {
	__ vmov(cgen_->ToDoubleRegister(saved_destination_), kScratchDoubleReg);
	} else if (saved_destination_->IsDoubleStackSlot()) {
	__ vstr(kScratchDoubleReg, cgen_->ToMemOperand(saved_destination_));
	} else {
	UNREACHABLE();
	}

	in_cycle_ = false;
	saved_destination_ = NULL;
	}


	void LGapResolver::EmitMove(int index) {
	LOperand* source = moves_[index].source();
	LOperand* destination = moves_[index].destination();

	// Dispatch on the source and destination operand kinds. Not all
	// combinations are possible.

	if (source->IsRegister()) {
	Register source_register = cgen_->ToRegister(source);
	if (destination->IsRegister()) {
	__ mov(cgen_->ToRegister(destination), source_register);
	} else {
	ASSERT(destination->IsStackSlot());
	__ str(source_register, cgen_->ToMemOperand(destination));
	}

	} else if (source->IsStackSlot()) {
	MemOperand source_operand = cgen_->ToMemOperand(source);
	if (destination->IsRegister()) {
	__ ldr(cgen_->ToRegister(destination), source_operand);
	} else {
	ASSERT(destination->IsStackSlot());
	MemOperand destination_operand = cgen_->ToMemOperand(destination);
	if (in_cycle_) {
	if (!destination_operand.OffsetIsUint12Encodable()) {
	// ip is overwritten while saving the value to the destination.
	// Therefore we can't use ip. It is OK if the read from the source
	// destroys ip, since that happens before the value is read.
	__ vldr(kScratchDoubleReg.low(), source_operand);
	__ vstr(kScratchDoubleReg.low(), destination_operand);
	} else {
	__ ldr(ip, source_operand);
	__ str(ip, destination_operand);
	}
	} else {
	__ ldr(kSavedValueRegister, source_operand);
	__ str(kSavedValueRegister, destination_operand);
	}
	}

	} else if (source->IsConstantOperand()) {
	Operand source_operand = cgen_->ToOperand(source);
	if (destination->IsRegister()) {
	__ mov(cgen_->ToRegister(destination), source_operand);
	} else {
	ASSERT(destination->IsStackSlot());
	ASSERT(!in_cycle_); // Constant moves happen after all cycles are gone.
	__ mov(kSavedValueRegister, source_operand);
	__ str(kSavedValueRegister, cgen_->ToMemOperand(destination));
	}

	} else if (source->IsDoubleRegister()) {
	DoubleRegister source_register = cgen_->ToDoubleRegister(source);
	if (destination->IsDoubleRegister()) {
	__ vmov(cgen_->ToDoubleRegister(destination), source_register);
	} else {
	ASSERT(destination->IsDoubleStackSlot());
	__ vstr(source_register, cgen_->ToMemOperand(destination));
	}

	} else if (source->IsDoubleStackSlot()) {
	MemOperand source_operand = cgen_->ToMemOperand(source);
	if (destination->IsDoubleRegister()) {
	__ vldr(cgen_->ToDoubleRegister(destination), source_operand);
	} else {
	ASSERT(destination->IsDoubleStackSlot());
	MemOperand destination_operand = cgen_->ToMemOperand(destination);
	if (in_cycle_) {
	// kSavedDoubleValueRegister was used to break the cycle,
	// but kSavedValueRegister is free.
	MemOperand source_high_operand =
	cgen_->ToHighMemOperand(source);
	MemOperand destination_high_operand =
	cgen_->ToHighMemOperand(destination);
	__ ldr(kSavedValueRegister, source_operand);
	__ str(kSavedValueRegister, destination_operand);
	__ ldr(kSavedValueRegister, source_high_operand);
	__ str(kSavedValueRegister, destination_high_operand);
	} else {
	__ vldr(kScratchDoubleReg, source_operand);
	__ vstr(kScratchDoubleReg, destination_operand);
	}
	}
	} else {
	UNREACHABLE();
	}

	moves_[index].Eliminate();
	}


	#undef __

	} } // namespace v8::internal