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// Copyright 2016 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/compiler/checkpoint-elimination.h"
#include "src/compiler/node-properties.h"
namespace v8 {
namespace internal {
namespace compiler {
CheckpointElimination::CheckpointElimination(Editor* editor)
: AdvancedReducer(editor) {}
namespace {
// The given checkpoint is redundant if it is effect-wise dominated by another
// checkpoint and there is no observable write in between. For now we consider
// a linear effect chain only instead of true effect-wise dominance.
bool IsRedundantCheckpoint(Node* node) {
Node* effect = NodeProperties::GetEffectInput(node);
while (effect->op()->HasProperty(Operator::kNoWrite) &&
effect->op()->EffectInputCount() == 1) {
if (effect->opcode() == IrOpcode::kCheckpoint) return true;
effect = NodeProperties::GetEffectInput(effect);
}
return false;
}
} // namespace
Reduction CheckpointElimination::ReduceCheckpoint(Node* node) {
DCHECK_EQ(IrOpcode::kCheckpoint, node->opcode());
if (IsRedundantCheckpoint(node)) {
return Replace(NodeProperties::GetEffectInput(node));
}
return NoChange();
}
Reduction CheckpointElimination::Reduce(Node* node) {
DisallowHeapAccess no_heap_access;
switch (node->opcode()) {
case IrOpcode::kCheckpoint:
return ReduceCheckpoint(node);
default:
break;
}
return NoChange();
}
} // namespace compiler
} // namespace internal
} // namespace v8