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Unified Diff: src/hydrogen-redundant-phi.cc

Issue 25896006: Simplify redundant phi elimination and use during canonicalization too. (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: Created 7 years, 2 months ago
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Index: src/hydrogen-redundant-phi.cc
diff --git a/src/hydrogen-redundant-phi.cc b/src/hydrogen-redundant-phi.cc
index 9c38200577d4994e79f5e1925039ca10a8c8a8c2..753da01897a856f69cdfcf094fb378a38f381144 100644
--- a/src/hydrogen-redundant-phi.cc
+++ b/src/hydrogen-redundant-phi.cc
@@ -31,37 +31,18 @@ namespace v8 {
namespace internal {
void HRedundantPhiEliminationPhase::Run() {
- // We do a simple fixed point iteration without any work list, because
- // machine-generated JavaScript can lead to a very dense Hydrogen graph with
- // an enormous work list and will consequently result in OOM. Experiments
- // showed that this simple algorithm is good enough, and even e.g. tracking
- // the set or range of blocks to consider is not a real improvement.
- bool need_another_iteration;
+ // Gather all phis from all blocks first.
const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
- ZoneList<HPhi*> redundant_phis(blocks->length(), zone());
- do {
- need_another_iteration = false;
- for (int i = 0; i < blocks->length(); ++i) {
- HBasicBlock* block = blocks->at(i);
- for (int j = 0; j < block->phis()->length(); j++) {
- HPhi* phi = block->phis()->at(j);
- HValue* replacement = phi->GetRedundantReplacement();
- if (replacement != NULL) {
- // Remember phi to avoid concurrent modification of the block's phis.
- redundant_phis.Add(phi, zone());
- for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
- HValue* value = it.value();
- value->SetOperandAt(it.index(), replacement);
- need_another_iteration |= value->IsPhi();
- }
- }
- }
- for (int i = 0; i < redundant_phis.length(); i++) {
- block->RemovePhi(redundant_phis[i]);
- }
- redundant_phis.Clear();
+ 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());
}
- } while (need_another_iteration);
+ }
+
+ // Iteratively reduce all phis in the list.
+ ProcessPhis(&all_phis);
#if DEBUG
// Make sure that we *really* removed all redundant phis.
@@ -73,4 +54,34 @@ void HRedundantPhiEliminationPhase::Run() {
#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) {
+ for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
+ HValue* value = it.value();
+ value->SetOperandAt(it.index(), replacement);
+ updated |= value->IsPhi(); // Iterate again if used in another phi.
+ }
+ phi->SetFlag(HValue::kIsDead);
+ phi->block()->RemovePhi(phi);
+ }
+ }
+ } while (updated);
+}
+
+
} } // namespace v8::internal
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