deps/v8/src/arm64/lithium-gap-resolver-arm64.cc
// Copyright 2013 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/arm64/delayed-masm-arm64-inl.h"
#include "src/arm64/lithium-codegen-arm64.h"
#include "src/arm64/lithium-gap-resolver-arm64.h"
namespace v8 {
namespace internal {
#define __ ACCESS_MASM((&masm_))
void DelayedGapMasm::EndDelayedUse() {
DelayedMasm::EndDelayedUse();
if (scratch_register_used()) {
DCHECK(ScratchRegister().Is(root));
DCHECK(!pending());
InitializeRootRegister();
reset_scratch_register_used();
}
}
LGapResolver::LGapResolver(LCodeGen* owner)
: cgen_(owner), masm_(owner, owner->masm()), moves_(32, owner->zone()),
root_index_(0), in_cycle_(false), saved_destination_(NULL) {
}
void LGapResolver::Resolve(LParallelMove* parallel_move) {
DCHECK(moves_.is_empty());
DCHECK(!masm_.pending());
// 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 we reach this move again.
PerformMove(i);
if (in_cycle_) RestoreValue();
}
}
// Perform the moves with constant sources.
for (int i = 0; i < moves_.length(); ++i) {
LMoveOperands move = moves_[i];
if (!move.IsEliminated()) {
DCHECK(move.source()->IsConstantOperand());
EmitMove(i);
}
}
__ EndDelayedUse();
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.
LMoveOperands& current_move = moves_[index];
DCHECK(!current_move.IsPending());
DCHECK(!current_move.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(current_move.source() != NULL); // Otherwise it will look eliminated.
LOperand* destination = current_move.destination();
current_move.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.
current_move.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) {
DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source()));
DCHECK(!in_cycle_);
// 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.
in_cycle_ = true;
LOperand* source = moves_[index].source();
saved_destination_ = moves_[index].destination();
if (source->IsRegister()) {
AcquireSavedValueRegister();
__ Mov(SavedValueRegister(), cgen_->ToRegister(source));
} else if (source->IsStackSlot()) {
AcquireSavedValueRegister();
__ Load(SavedValueRegister(), cgen_->ToMemOperand(source));
} else if (source->IsDoubleRegister()) {
__ Fmov(SavedFPValueRegister(), cgen_->ToDoubleRegister(source));
} else if (source->IsDoubleStackSlot()) {
__ Load(SavedFPValueRegister(), cgen_->ToMemOperand(source));
} else {
UNREACHABLE();
}
// Mark this move as resolved.
// This move will be actually performed by moving the saved value to this
// move's destination in LGapResolver::RestoreValue().
moves_[index].Eliminate();
}
void LGapResolver::RestoreValue() {
DCHECK(in_cycle_);
DCHECK(saved_destination_ != NULL);
if (saved_destination_->IsRegister()) {
__ Mov(cgen_->ToRegister(saved_destination_), SavedValueRegister());
ReleaseSavedValueRegister();
} else if (saved_destination_->IsStackSlot()) {
__ Store(SavedValueRegister(), cgen_->ToMemOperand(saved_destination_));
ReleaseSavedValueRegister();
} else if (saved_destination_->IsDoubleRegister()) {
__ Fmov(cgen_->ToDoubleRegister(saved_destination_),
SavedFPValueRegister());
} else if (saved_destination_->IsDoubleStackSlot()) {
__ Store(SavedFPValueRegister(), 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());
__ Store(source_register, cgen_->ToMemOperand(destination));
}
} else if (source->IsStackSlot()) {
MemOperand source_operand = cgen_->ToMemOperand(source);
if (destination->IsRegister()) {
__ Load(cgen_->ToRegister(destination), source_operand);
} else {
DCHECK(destination->IsStackSlot());
EmitStackSlotMove(index);
}
} else if (source->IsConstantOperand()) {
LConstantOperand* constant_source = LConstantOperand::cast(source);
if (destination->IsRegister()) {
Register dst = cgen_->ToRegister(destination);
if (cgen_->IsSmi(constant_source)) {
__ Mov(dst, cgen_->ToSmi(constant_source));
} else if (cgen_->IsInteger32Constant(constant_source)) {
__ Mov(dst, cgen_->ToInteger32(constant_source));
} else {
__ LoadObject(dst, cgen_->ToHandle(constant_source));
}
} else if (destination->IsDoubleRegister()) {
DoubleRegister result = cgen_->ToDoubleRegister(destination);
__ Fmov(result, cgen_->ToDouble(constant_source));
} else {
DCHECK(destination->IsStackSlot());
DCHECK(!in_cycle_); // Constant moves happen after all cycles are gone.
if (cgen_->IsSmi(constant_source)) {
Smi* smi = cgen_->ToSmi(constant_source);
__ StoreConstant(reinterpret_cast<intptr_t>(smi),
cgen_->ToMemOperand(destination));
} else if (cgen_->IsInteger32Constant(constant_source)) {
__ StoreConstant(cgen_->ToInteger32(constant_source),
cgen_->ToMemOperand(destination));
} else {
Handle<Object> handle = cgen_->ToHandle(constant_source);
AllowDeferredHandleDereference smi_object_check;
if (handle->IsSmi()) {
Object* obj = *handle;
DCHECK(!obj->IsHeapObject());
__ StoreConstant(reinterpret_cast<intptr_t>(obj),
cgen_->ToMemOperand(destination));
} else {
AcquireSavedValueRegister();
__ LoadObject(SavedValueRegister(), handle);
__ Store(SavedValueRegister(), cgen_->ToMemOperand(destination));
ReleaseSavedValueRegister();
}
}
}
} else if (source->IsDoubleRegister()) {
DoubleRegister src = cgen_->ToDoubleRegister(source);
if (destination->IsDoubleRegister()) {
__ Fmov(cgen_->ToDoubleRegister(destination), src);
} else {
DCHECK(destination->IsDoubleStackSlot());
__ Store(src, cgen_->ToMemOperand(destination));
}
} else if (source->IsDoubleStackSlot()) {
MemOperand src = cgen_->ToMemOperand(source);
if (destination->IsDoubleRegister()) {
__ Load(cgen_->ToDoubleRegister(destination), src);
} else {
DCHECK(destination->IsDoubleStackSlot());
EmitStackSlotMove(index);
}
} else {
UNREACHABLE();
}
// The move has been emitted, we can eliminate it.
moves_[index].Eliminate();
}
} } // namespace v8::internal