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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/crankshaft/hydrogen-redundant-phi.h"
#include "src/objects-inl.h"
namespace v8 {
namespace internal {
void HRedundantPhiEliminationPhase::Run() {
// Gather all phis from all blocks first.
const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
ZoneList<HPhi*> all_phis(blocks->length(), zone());
for (int i = 0; i < blocks->length(); ++i) {
HBasicBlock* block = blocks->at(i);
for (int j = 0; j < block->phis()->length(); j++) {
all_phis.Add(block->phis()->at(j), zone());
}
}
// Iteratively reduce all phis in the list.
ProcessPhis(&all_phis);
#if DEBUG
// Make sure that we *really* removed all redundant phis.
for (int i = 0; i < blocks->length(); ++i) {
for (int j = 0; j < blocks->at(i)->phis()->length(); j++) {
DCHECK(blocks->at(i)->phis()->at(j)->GetRedundantReplacement() == NULL);
}
}
#endif
}
void HRedundantPhiEliminationPhase::ProcessBlock(HBasicBlock* block) {
ProcessPhis(block->phis());
}
void HRedundantPhiEliminationPhase::ProcessPhis(const ZoneList<HPhi*>* phis) {
bool updated;
do {
// Iterately replace all redundant phis in the given list.
updated = false;
for (int i = 0; i < phis->length(); i++) {
HPhi* phi = phis->at(i);
if (phi->CheckFlag(HValue::kIsDead)) continue; // Already replaced.
HValue* replacement = phi->GetRedundantReplacement();
if (replacement != NULL) {
phi->SetFlag(HValue::kIsDead);
for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
HValue* value = it.value();
value->SetOperandAt(it.index(), replacement);
// Iterate again if used in another non-dead phi.
updated |= value->IsPhi() && !value->CheckFlag(HValue::kIsDead);
}
phi->block()->RemovePhi(phi);
}
}
} while (updated);
}
} // namespace internal
} // namespace v8
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