// Copyright 2016 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "src/compiler/checkpoint-elimination.h"
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#include "src/compiler/node-properties.h"
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namespace v8 {
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namespace internal {
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namespace compiler {
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CheckpointElimination::CheckpointElimination(Editor* editor)
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: AdvancedReducer(editor) {}
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namespace {
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// The given checkpoint is redundant if it is effect-wise dominated by another
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// checkpoint and there is no observable write in between. For now we consider
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// a linear effect chain only instead of true effect-wise dominance.
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bool IsRedundantCheckpoint(Node* node) {
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Node* effect = NodeProperties::GetEffectInput(node);
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while (effect->op()->HasProperty(Operator::kNoWrite) &&
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effect->op()->EffectInputCount() == 1) {
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if (effect->opcode() == IrOpcode::kCheckpoint) return true;
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effect = NodeProperties::GetEffectInput(effect);
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}
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return false;
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}
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} // namespace
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Reduction CheckpointElimination::ReduceCheckpoint(Node* node) {
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DCHECK_EQ(IrOpcode::kCheckpoint, node->opcode());
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if (IsRedundantCheckpoint(node)) {
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return Replace(NodeProperties::GetEffectInput(node));
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}
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return NoChange();
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}
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Reduction CheckpointElimination::Reduce(Node* node) {
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DisallowHeapAccess no_heap_access;
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switch (node->opcode()) {
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case IrOpcode::kCheckpoint:
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return ReduceCheckpoint(node);
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default:
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break;
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}
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return NoChange();
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}
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} // namespace compiler
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} // namespace internal
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} // namespace v8
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