root/src/mips/lithium-gap-resolver-mips.cc
/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- saved_destination_
- BuildInitialMoveList
- PerformMove
- Verify
- BreakCycle
- RestoreValue
- EmitMove
// 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,
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#include "v8.h"
#include "mips/lithium-gap-resolver-mips.h"
#include "mips/lithium-codegen-mips.h"
namespace v8 {
namespace internal {
LGapResolver::LGapResolver(LCodeGen* owner)
: cgen_(owner),
moves_(32, owner->zone()),
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, 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.
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(kLithiumScratchReg, cgen_->ToRegister(source));
} else if (source->IsStackSlot()) {
__ lw(kLithiumScratchReg, cgen_->ToMemOperand(source));
} else if (source->IsDoubleRegister()) {
__ mov_d(kLithiumScratchDouble, cgen_->ToDoubleRegister(source));
} else if (source->IsDoubleStackSlot()) {
__ ldc1(kLithiumScratchDouble, 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 kLithiumScratchReg or kLithiumScratchDouble.
if (saved_destination_->IsRegister()) {
__ mov(cgen_->ToRegister(saved_destination_), kLithiumScratchReg);
} else if (saved_destination_->IsStackSlot()) {
__ sw(kLithiumScratchReg, cgen_->ToMemOperand(saved_destination_));
} else if (saved_destination_->IsDoubleRegister()) {
__ mov_d(cgen_->ToDoubleRegister(saved_destination_),
kLithiumScratchDouble);
} else if (saved_destination_->IsDoubleStackSlot()) {
__ sdc1(kLithiumScratchDouble,
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());
__ sw(source_register, cgen_->ToMemOperand(destination));
}
} else if (source->IsStackSlot()) {
MemOperand source_operand = cgen_->ToMemOperand(source);
if (destination->IsRegister()) {
__ lw(cgen_->ToRegister(destination), source_operand);
} else {
ASSERT(destination->IsStackSlot());
MemOperand destination_operand = cgen_->ToMemOperand(destination);
if (in_cycle_) {
if (!destination_operand.OffsetIsInt16Encodable()) {
// 'at' is overwritten while saving the value to the destination.
// Therefore we can't use 'at'. It is OK if the read from the source
// destroys 'at', since that happens before the value is read.
// This uses only a single reg of the double reg-pair.
__ lwc1(kLithiumScratchDouble, source_operand);
__ swc1(kLithiumScratchDouble, destination_operand);
} else {
__ lw(at, source_operand);
__ sw(at, destination_operand);
}
} else {
__ lw(kLithiumScratchReg, source_operand);
__ sw(kLithiumScratchReg, destination_operand);
}
}
} else if (source->IsConstantOperand()) {
LConstantOperand* constant_source = LConstantOperand::cast(source);
if (destination->IsRegister()) {
Register dst = cgen_->ToRegister(destination);
if (cgen_->IsInteger32(constant_source)) {
__ li(dst, Operand(cgen_->ToInteger32(constant_source)));
} else {
__ LoadObject(dst, cgen_->ToHandle(constant_source));
}
} else {
ASSERT(destination->IsStackSlot());
ASSERT(!in_cycle_); // Constant moves happen after all cycles are gone.
if (cgen_->IsInteger32(constant_source)) {
__ li(kLithiumScratchReg,
Operand(cgen_->ToInteger32(constant_source)));
} else {
__ LoadObject(kLithiumScratchReg,
cgen_->ToHandle(constant_source));
}
__ sw(kLithiumScratchReg, cgen_->ToMemOperand(destination));
}
} else if (source->IsDoubleRegister()) {
DoubleRegister source_register = cgen_->ToDoubleRegister(source);
if (destination->IsDoubleRegister()) {
__ mov_d(cgen_->ToDoubleRegister(destination), source_register);
} else {
ASSERT(destination->IsDoubleStackSlot());
MemOperand destination_operand = cgen_->ToMemOperand(destination);
__ sdc1(source_register, destination_operand);
}
} else if (source->IsDoubleStackSlot()) {
MemOperand source_operand = cgen_->ToMemOperand(source);
if (destination->IsDoubleRegister()) {
__ ldc1(cgen_->ToDoubleRegister(destination), source_operand);
} else {
ASSERT(destination->IsDoubleStackSlot());
MemOperand destination_operand = cgen_->ToMemOperand(destination);
if (in_cycle_) {
// kLithiumScratchDouble was used to break the cycle,
// but kLithiumScratchReg is free.
MemOperand source_high_operand =
cgen_->ToHighMemOperand(source);
MemOperand destination_high_operand =
cgen_->ToHighMemOperand(destination);
__ lw(kLithiumScratchReg, source_operand);
__ sw(kLithiumScratchReg, destination_operand);
__ lw(kLithiumScratchReg, source_high_operand);
__ sw(kLithiumScratchReg, destination_high_operand);
} else {
__ ldc1(kLithiumScratchDouble, source_operand);
__ sdc1(kLithiumScratchDouble, destination_operand);
}
}
} else {
UNREACHABLE();
}
moves_[index].Eliminate();
}
#undef __
} } // namespace v8::internal