deps/v8/src/ia32/lithium-gap-resolver-ia32.cc
// Copyright 2011 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"
#if V8_TARGET_ARCH_IA32
#include "src/ia32/lithium-codegen-ia32.h"
#include "src/ia32/lithium-gap-resolver-ia32.h"
namespace v8 {
namespace internal {
LGapResolver::LGapResolver(LCodeGen* owner)
: cgen_(owner),
moves_(32, owner->zone()),
source_uses_(),
destination_uses_(),
spilled_register_(-1) {}
void LGapResolver::Resolve(LParallelMove* parallel_move) {
DCHECK(HasBeenReset());
// 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()) {
PerformMove(i);
}
}
// 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);
}
}
Finish();
DCHECK(HasBeenReset());
}
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()) AddMove(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 use operand swaps to resolve cycles,
// which means that a call to PerformMove could change any source operand
// in the move graph.
DCHECK(!moves_[index].IsPending());
DCHECK(!moves_[index].IsRedundant());
// Clear this move's destination to indicate a pending move. The actual
// destination is saved on the side.
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()) {
// Though PerformMove can change any source operand in the move graph,
// this call cannot create a blocking move via a swap (this loop does
// not miss any). Assume there is a non-blocking move with source A
// and this move is blocked on source B and there is a swap of A and
// B. Then A and B must be involved in the same cycle (or they would
// not be swapped). Since this move's destination is B and there is
// only a single incoming edge to an operand, this move must also be
// involved in the same cycle. In that case, the blocking move will
// be created but will be "pending" when we return from PerformMove.
PerformMove(i);
}
}
// We are about to resolve this move and don't need it marked as
// pending, so restore its destination.
moves_[index].set_destination(destination);
// This move's source may have changed due to swaps to resolve cycles and
// so it may now be the last move in the cycle. If so remove it.
if (moves_[index].source()->Equals(destination)) {
RemoveMove(index);
return;
}
// The move may be blocked on a (at most one) pending move, in which case
// we have a cycle. Search for such a blocking move and perform a swap to
// resolve it.
for (int i = 0; i < moves_.length(); ++i) {
LMoveOperands other_move = moves_[i];
if (other_move.Blocks(destination)) {
DCHECK(other_move.IsPending());
EmitSwap(index);
return;
}
}
// This move is not blocked.
EmitMove(index);
}
void LGapResolver::AddMove(LMoveOperands move) {
LOperand* source = move.source();
if (source->IsRegister()) ++source_uses_[source->index()];
LOperand* destination = move.destination();
if (destination->IsRegister()) ++destination_uses_[destination->index()];
moves_.Add(move, cgen_->zone());
}
void LGapResolver::RemoveMove(int index) {
LOperand* source = moves_[index].source();
if (source->IsRegister()) {
--source_uses_[source->index()];
DCHECK(source_uses_[source->index()] >= 0);
}
LOperand* destination = moves_[index].destination();
if (destination->IsRegister()) {
--destination_uses_[destination->index()];
DCHECK(destination_uses_[destination->index()] >= 0);
}
moves_[index].Eliminate();
}
int LGapResolver::CountSourceUses(LOperand* operand) {
int count = 0;
for (int i = 0; i < moves_.length(); ++i) {
if (!moves_[i].IsEliminated() && moves_[i].source()->Equals(operand)) {
++count;
}
}
return count;
}
Register LGapResolver::GetFreeRegisterNot(Register reg) {
int skip_index = reg.is(no_reg) ? -1 : Register::ToAllocationIndex(reg);
for (int i = 0; i < Register::NumAllocatableRegisters(); ++i) {
if (source_uses_[i] == 0 && destination_uses_[i] > 0 && i != skip_index) {
return Register::FromAllocationIndex(i);
}
}
return no_reg;
}
bool LGapResolver::HasBeenReset() {
if (!moves_.is_empty()) return false;
if (spilled_register_ >= 0) return false;
for (int i = 0; i < Register::NumAllocatableRegisters(); ++i) {
if (source_uses_[i] != 0) return false;
if (destination_uses_[i] != 0) return false;
}
return true;
}
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
}
#define __ ACCESS_MASM(cgen_->masm())
void LGapResolver::Finish() {
if (spilled_register_ >= 0) {
__ pop(Register::FromAllocationIndex(spilled_register_));
spilled_register_ = -1;
}
moves_.Rewind(0);
}
void LGapResolver::EnsureRestored(LOperand* operand) {
if (operand->IsRegister() && operand->index() == spilled_register_) {
__ pop(Register::FromAllocationIndex(spilled_register_));
spilled_register_ = -1;
}
}
Register LGapResolver::EnsureTempRegister() {
// 1. We may have already spilled to create a temp register.
if (spilled_register_ >= 0) {
return Register::FromAllocationIndex(spilled_register_);
}
// 2. We may have a free register that we can use without spilling.
Register free = GetFreeRegisterNot(no_reg);
if (!free.is(no_reg)) return free;
// 3. Prefer to spill a register that is not used in any remaining move
// because it will not need to be restored until the end.
for (int i = 0; i < Register::NumAllocatableRegisters(); ++i) {
if (source_uses_[i] == 0 && destination_uses_[i] == 0) {
Register scratch = Register::FromAllocationIndex(i);
__ push(scratch);
spilled_register_ = i;
return scratch;
}
}
// 4. Use an arbitrary register. Register 0 is as arbitrary as any other.
Register scratch = Register::FromAllocationIndex(0);
__ push(scratch);
spilled_register_ = 0;
return scratch;
}
void LGapResolver::EmitMove(int index) {
LOperand* source = moves_[index].source();
LOperand* destination = moves_[index].destination();
EnsureRestored(source);
EnsureRestored(destination);
// Dispatch on the source and destination operand kinds. Not all
// combinations are possible.
if (source->IsRegister()) {
DCHECK(destination->IsRegister() || destination->IsStackSlot());
Register src = cgen_->ToRegister(source);
Operand dst = cgen_->ToOperand(destination);
__ mov(dst, src);
} else if (source->IsStackSlot()) {
DCHECK(destination->IsRegister() || destination->IsStackSlot());
Operand src = cgen_->ToOperand(source);
if (destination->IsRegister()) {
Register dst = cgen_->ToRegister(destination);
__ mov(dst, src);
} else {
// Spill on demand to use a temporary register for memory-to-memory
// moves.
Register tmp = EnsureTempRegister();
Operand dst = cgen_->ToOperand(destination);
__ mov(tmp, src);
__ mov(dst, tmp);
}
} 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)) {
__ Move(dst, cgen_->ToImmediate(constant_source, r));
} else {
__ LoadObject(dst, cgen_->ToHandle(constant_source));
}
} else if (destination->IsDoubleRegister()) {
double v = cgen_->ToDouble(constant_source);
uint64_t int_val = BitCast<uint64_t, double>(v);
int32_t lower = static_cast<int32_t>(int_val);
int32_t upper = static_cast<int32_t>(int_val >> kBitsPerInt);
XMMRegister dst = cgen_->ToDoubleRegister(destination);
if (int_val == 0) {
__ xorps(dst, dst);
} else {
__ push(Immediate(upper));
__ push(Immediate(lower));
__ movsd(dst, Operand(esp, 0));
__ add(esp, Immediate(kDoubleSize));
}
} else {
DCHECK(destination->IsStackSlot());
Operand dst = cgen_->ToOperand(destination);
Representation r = cgen_->IsSmi(constant_source)
? Representation::Smi() : Representation::Integer32();
if (cgen_->IsInteger32(constant_source)) {
__ Move(dst, cgen_->ToImmediate(constant_source, r));
} else {
Register tmp = EnsureTempRegister();
__ LoadObject(tmp, cgen_->ToHandle(constant_source));
__ mov(dst, tmp);
}
}
} else if (source->IsDoubleRegister()) {
XMMRegister src = cgen_->ToDoubleRegister(source);
if (destination->IsDoubleRegister()) {
XMMRegister dst = cgen_->ToDoubleRegister(destination);
__ movaps(dst, src);
} else {
DCHECK(destination->IsDoubleStackSlot());
Operand dst = cgen_->ToOperand(destination);
__ movsd(dst, src);
}
} else if (source->IsDoubleStackSlot()) {
DCHECK(destination->IsDoubleRegister() ||
destination->IsDoubleStackSlot());
Operand src = cgen_->ToOperand(source);
if (destination->IsDoubleRegister()) {
XMMRegister dst = cgen_->ToDoubleRegister(destination);
__ movsd(dst, src);
} else {
// We rely on having xmm0 available as a fixed scratch register.
Operand dst = cgen_->ToOperand(destination);
__ movsd(xmm0, src);
__ movsd(dst, xmm0);
}
} else {
UNREACHABLE();
}
RemoveMove(index);
}
void LGapResolver::EmitSwap(int index) {
LOperand* source = moves_[index].source();
LOperand* destination = moves_[index].destination();
EnsureRestored(source);
EnsureRestored(destination);
// Dispatch on the source and destination operand kinds. Not all
// combinations are possible.
if (source->IsRegister() && destination->IsRegister()) {
// Register-register.
Register src = cgen_->ToRegister(source);
Register dst = cgen_->ToRegister(destination);
__ xchg(dst, src);
} else if ((source->IsRegister() && destination->IsStackSlot()) ||
(source->IsStackSlot() && destination->IsRegister())) {
// Register-memory. Use a free register as a temp if possible. Do not
// spill on demand because the simple spill implementation cannot avoid
// spilling src at this point.
Register tmp = GetFreeRegisterNot(no_reg);
Register reg =
cgen_->ToRegister(source->IsRegister() ? source : destination);
Operand mem =
cgen_->ToOperand(source->IsRegister() ? destination : source);
if (tmp.is(no_reg)) {
__ xor_(reg, mem);
__ xor_(mem, reg);
__ xor_(reg, mem);
} else {
__ mov(tmp, mem);
__ mov(mem, reg);
__ mov(reg, tmp);
}
} else if (source->IsStackSlot() && destination->IsStackSlot()) {
// Memory-memory. Spill on demand to use a temporary. If there is a
// free register after that, use it as a second temporary.
Register tmp0 = EnsureTempRegister();
Register tmp1 = GetFreeRegisterNot(tmp0);
Operand src = cgen_->ToOperand(source);
Operand dst = cgen_->ToOperand(destination);
if (tmp1.is(no_reg)) {
// Only one temp register available to us.
__ mov(tmp0, dst);
__ xor_(tmp0, src);
__ xor_(src, tmp0);
__ xor_(tmp0, src);
__ mov(dst, tmp0);
} else {
__ mov(tmp0, dst);
__ mov(tmp1, src);
__ mov(dst, tmp1);
__ mov(src, tmp0);
}
} else if (source->IsDoubleRegister() && destination->IsDoubleRegister()) {
// XMM register-register swap. We rely on having xmm0
// available as a fixed scratch register.
XMMRegister src = cgen_->ToDoubleRegister(source);
XMMRegister dst = cgen_->ToDoubleRegister(destination);
__ movaps(xmm0, src);
__ movaps(src, dst);
__ movaps(dst, xmm0);
} else if (source->IsDoubleRegister() || destination->IsDoubleRegister()) {
// XMM register-memory swap. We rely on having xmm0
// available as a fixed scratch register.
DCHECK(source->IsDoubleStackSlot() || destination->IsDoubleStackSlot());
XMMRegister reg = cgen_->ToDoubleRegister(source->IsDoubleRegister()
? source
: destination);
Operand other =
cgen_->ToOperand(source->IsDoubleRegister() ? destination : source);
__ movsd(xmm0, other);
__ movsd(other, reg);
__ movaps(reg, xmm0);
} else if (source->IsDoubleStackSlot() && destination->IsDoubleStackSlot()) {
// Double-width memory-to-memory. Spill on demand to use a general
// purpose temporary register and also rely on having xmm0 available as
// a fixed scratch register.
Register tmp = EnsureTempRegister();
Operand src0 = cgen_->ToOperand(source);
Operand src1 = cgen_->HighOperand(source);
Operand dst0 = cgen_->ToOperand(destination);
Operand dst1 = cgen_->HighOperand(destination);
__ movsd(xmm0, dst0); // Save destination in xmm0.
__ mov(tmp, src0); // Then use tmp to copy source to destination.
__ mov(dst0, tmp);
__ mov(tmp, src1);
__ mov(dst1, tmp);
__ movsd(src0, xmm0);
} else {
// No other combinations are possible.
UNREACHABLE();
}
// The swap of source and destination has executed a move from source to
// destination.
RemoveMove(index);
// Any unperformed (including pending) move with a source of either
// this move's source or destination needs to have their source
// changed to reflect the state of affairs after the swap.
for (int i = 0; i < moves_.length(); ++i) {
LMoveOperands other_move = moves_[i];
if (other_move.Blocks(source)) {
moves_[i].set_source(destination);
} else if (other_move.Blocks(destination)) {
moves_[i].set_source(source);
}
}
// In addition to swapping the actual uses as sources, we need to update
// the use counts.
if (source->IsRegister() && destination->IsRegister()) {
int temp = source_uses_[source->index()];
source_uses_[source->index()] = source_uses_[destination->index()];
source_uses_[destination->index()] = temp;
} else if (source->IsRegister()) {
// We don't have use counts for non-register operands like destination.
// Compute those counts now.
source_uses_[source->index()] = CountSourceUses(source);
} else if (destination->IsRegister()) {
source_uses_[destination->index()] = CountSourceUses(destination);
}
}
#undef __
} } // namespace v8::internal
#endif // V8_TARGET_ARCH_IA32