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// 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.h"
#include "src/lithium.h"
namespace v8 {
namespace internal {
class LCodeGen;
class LGapResolver;
class DelayedGapMasm : public DelayedMasm {
DelayedGapMasm(LCodeGen* owner, MacroAssembler* masm)
: DelayedMasm(owner, masm, root) {
// We use the root register as an extra scratch register.
// The root register has two advantages:
// - It is not in crankshaft allocatable registers list, so it can't
// interfere with the allocatable registers.
// - We don't need to push it on the stack, as we can reload it with its
// value once we have finish.
void EndDelayedUse();
class LGapResolver BASE_EMBEDDED {
explicit LGapResolver(LCodeGen* owner);
// Resolve a set of parallel moves, emitting assembler instructions.
void Resolve(LParallelMove* parallel_move);
// Build the initial list of moves.
void BuildInitialMoveList(LParallelMove* parallel_move);
// Perform the move at the moves_ index in question (possibly requiring
// other moves to satisfy dependencies).
void PerformMove(int index);
// If a cycle is found in the series of moves, save the blocking value to
// a scratch register. The cycle must be found by hitting the root of the
// depth-first search.
void BreakCycle(int index);
// After a cycle has been resolved, restore the value from the scratch
// register to its proper destination.
void RestoreValue();
// Emit a move and remove it from the move graph.
void EmitMove(int index);
// Emit a move from one stack slot to another.
void EmitStackSlotMove(int index) {
masm_.StackSlotMove(moves_[index].source(), moves_[index].destination());
// Verify the move list before performing moves.
void Verify();
// Registers used to solve cycles.
const Register& SavedValueRegister() {
return masm_.ScratchRegister();
// The scratch register is used to break cycles and to store constant.
// These two methods switch from one mode to the other.
void AcquireSavedValueRegister() { masm_.AcquireScratchRegister(); }
void ReleaseSavedValueRegister() { masm_.ReleaseScratchRegister(); }
const FPRegister& SavedFPValueRegister() {
// We use the Crankshaft floating-point scratch register to break a cycle
// involving double values as the MacroAssembler will not need it for the
// operations performed by the gap resolver.
return crankshaft_fp_scratch;
LCodeGen* cgen_;
DelayedGapMasm masm_;
// List of moves not yet resolved.
ZoneList<LMoveOperands> moves_;
int root_index_;
bool in_cycle_;
LOperand* saved_destination_;
} } // namespace v8::internal