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

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "src/v8.h"

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

 namespace v8 {
 namespace internal {

 // We use the root register to spill a value while breaking a cycle in parallel
 // moves. We don't need access to roots while resolving the move list and using
 // the root register has two advantages:
 //  - It is not in crankshaft allocatable registers list, so it can't interfere
 //    with any of the moves we are resolving.
 //  - We don't need to push it on the stack, as we can reload it with its value
 //    once we have resolved a cycle.
 #define kSavedValueRegister kRootRegister


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


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


 void LGapResolver::Resolve(LParallelMove* parallel_move) {
   DCHECK(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()) {
       DCHECK(moves_[i].source()->IsConstantOperand());
       EmitMove(i);
     }
   }

   if (need_to_restore_root_) {
     DCHECK(kSavedValueRegister.is(kRootRegister));
     __ InitializeRootRegister();
     need_to_restore_root_ = false;
   }

   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, cgen_->zone());
   }
   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.
   DCHECK(!moves_[index].IsPending());
   DCHECK(!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.
   DCHECK(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)) {
     DCHECK(other_move.IsPending());
     BreakCycle(index);
     return;
   }

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


 void LGapResolver::Verify() {
 #ifdef ENABLE_SLOW_DCHECKS
   // 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_DCHECK(!destination->Equals(moves_[j].destination()));
     }
   }
 #endif
 }


 void LGapResolver::BreakCycle(int index) {
   // We save in a register the source of that move and we remember its
   // destination. Then we mark this move as resolved so the cycle is
   // broken and we can perform the other moves.
   DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source()));
   DCHECK(!in_cycle_);
   in_cycle_ = true;
   LOperand* source = moves_[index].source();
   saved_destination_ = moves_[index].destination();
   if (source->IsRegister()) {
     need_to_restore_root_ = true;
     __ mov(kSavedValueRegister, cgen_->ToRegister(source));
   } else if (source->IsStackSlot()) {
     need_to_restore_root_ = true;
     __ 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() {
   DCHECK(in_cycle_);
   DCHECK(saved_destination_ != NULL);

   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 {
       DCHECK(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 {
       DCHECK(destination->IsStackSlot());
       MemOperand destination_operand = cgen_->ToMemOperand(destination);
       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 if (source->IsConstantOperand()) {
     LConstantOperand* constant_source = LConstantOperand::cast(source);
     if (destination->IsRegister()) {
       Register dst = cgen_->ToRegister(destination);
       Representation r = cgen_->IsSmi(constant_source)
           ? Representation::Smi() : Representation::Integer32();
       if (cgen_->IsInteger32(constant_source)) {
         __ mov(dst, Operand(cgen_->ToRepresentation(constant_source, r)));
       } else {
         __ Move(dst, cgen_->ToHandle(constant_source));
       }
     } else if (destination->IsDoubleRegister()) {
       DwVfpRegister result = cgen_->ToDoubleRegister(destination);
       double v = cgen_->ToDouble(constant_source);
       __ Vmov(result, v, ip);
     } else {
       DCHECK(destination->IsStackSlot());
       DCHECK(!in_cycle_);  // Constant moves happen after all cycles are gone.
       need_to_restore_root_ = true;
       Representation r = cgen_->IsSmi(constant_source)
           ? Representation::Smi() : Representation::Integer32();
       if (cgen_->IsInteger32(constant_source)) {
         __ mov(kSavedValueRegister,
                Operand(cgen_->ToRepresentation(constant_source, r)));
       } else {
         __ Move(kSavedValueRegister, cgen_->ToHandle(constant_source));
       }
       __ str(kSavedValueRegister, cgen_->ToMemOperand(destination));
     }

   } else if (source->IsDoubleRegister()) {
     DwVfpRegister source_register = cgen_->ToDoubleRegister(source);
     if (destination->IsDoubleRegister()) {
       __ vmov(cgen_->ToDoubleRegister(destination), source_register);
     } else {
       DCHECK(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 {
       DCHECK(destination->IsDoubleStackSlot());
       MemOperand destination_operand = cgen_->ToMemOperand(destination);
       if (in_cycle_) {
         // kScratchDoubleReg was used to break the cycle.
         __ vstm(db_w, sp, kScratchDoubleReg, kScratchDoubleReg);
         __ vldr(kScratchDoubleReg, source_operand);
         __ vstr(kScratchDoubleReg, destination_operand);
         __ vldm(ia_w, sp, kScratchDoubleReg, kScratchDoubleReg);
       } 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.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "src/v8.h"

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

	namespace v8 {
	namespace internal {

	// We use the root register to spill a value while breaking a cycle in parallel
	// moves. We don't need access to roots while resolving the move list and using
	// the root register has two advantages:
	// - It is not in crankshaft allocatable registers list, so it can't interfere
	// with any of the moves we are resolving.
	// - We don't need to push it on the stack, as we can reload it with its value
	// once we have resolved a cycle.
	#define kSavedValueRegister kRootRegister


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


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


	void LGapResolver::Resolve(LParallelMove* parallel_move) {
	DCHECK(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()) {
	DCHECK(moves_[i].source()->IsConstantOperand());
	EmitMove(i);
	}
	}

	if (need_to_restore_root_) {
	DCHECK(kSavedValueRegister.is(kRootRegister));
	__ InitializeRootRegister();
	need_to_restore_root_ = false;
	}

	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, cgen_->zone());
	}
	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.
	DCHECK(!moves_[index].IsPending());
	DCHECK(!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.
	DCHECK(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)) {
	DCHECK(other_move.IsPending());
	BreakCycle(index);
	return;
	}

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


	void LGapResolver::Verify() {
	#ifdef ENABLE_SLOW_DCHECKS
	// 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_DCHECK(!destination->Equals(moves_[j].destination()));
	}
	}
	#endif
	}


	void LGapResolver::BreakCycle(int index) {
	// We save in a register the source of that move and we remember its
	// destination. Then we mark this move as resolved so the cycle is
	// broken and we can perform the other moves.
	DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source()));
	DCHECK(!in_cycle_);
	in_cycle_ = true;
	LOperand* source = moves_[index].source();
	saved_destination_ = moves_[index].destination();
	if (source->IsRegister()) {
	need_to_restore_root_ = true;
	__ mov(kSavedValueRegister, cgen_->ToRegister(source));
	} else if (source->IsStackSlot()) {
	need_to_restore_root_ = true;
	__ 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() {
	DCHECK(in_cycle_);
	DCHECK(saved_destination_ != NULL);

	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 {
	DCHECK(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 {
	DCHECK(destination->IsStackSlot());
	MemOperand destination_operand = cgen_->ToMemOperand(destination);
	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 if (source->IsConstantOperand()) {
	LConstantOperand* constant_source = LConstantOperand::cast(source);
	if (destination->IsRegister()) {
	Register dst = cgen_->ToRegister(destination);
	Representation r = cgen_->IsSmi(constant_source)
	? Representation::Smi() : Representation::Integer32();
	if (cgen_->IsInteger32(constant_source)) {
	__ mov(dst, Operand(cgen_->ToRepresentation(constant_source, r)));
	} else {
	__ Move(dst, cgen_->ToHandle(constant_source));
	}
	} else if (destination->IsDoubleRegister()) {
	DwVfpRegister result = cgen_->ToDoubleRegister(destination);
	double v = cgen_->ToDouble(constant_source);
	__ Vmov(result, v, ip);
	} else {
	DCHECK(destination->IsStackSlot());
	DCHECK(!in_cycle_); // Constant moves happen after all cycles are gone.
	need_to_restore_root_ = true;
	Representation r = cgen_->IsSmi(constant_source)
	? Representation::Smi() : Representation::Integer32();
	if (cgen_->IsInteger32(constant_source)) {
	__ mov(kSavedValueRegister,
	Operand(cgen_->ToRepresentation(constant_source, r)));
	} else {
	__ Move(kSavedValueRegister, cgen_->ToHandle(constant_source));
	}
	__ str(kSavedValueRegister, cgen_->ToMemOperand(destination));
	}

	} else if (source->IsDoubleRegister()) {
	DwVfpRegister source_register = cgen_->ToDoubleRegister(source);
	if (destination->IsDoubleRegister()) {
	__ vmov(cgen_->ToDoubleRegister(destination), source_register);
	} else {
	DCHECK(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 {
	DCHECK(destination->IsDoubleStackSlot());
	MemOperand destination_operand = cgen_->ToMemOperand(destination);
	if (in_cycle_) {
	// kScratchDoubleReg was used to break the cycle.
	__ vstm(db_w, sp, kScratchDoubleReg, kScratchDoubleReg);
	__ vldr(kScratchDoubleReg, source_operand);
	__ vstr(kScratchDoubleReg, destination_operand);
	__ vldm(ia_w, sp, kScratchDoubleReg, kScratchDoubleReg);
	} else {
	__ vldr(kScratchDoubleReg, source_operand);
	__ vstr(kScratchDoubleReg, destination_operand);
	}
	}
	} else {
	UNREACHABLE();
	}

	moves_[index].Eliminate();
	}


	#undef __

	} } // namespace v8::internal