Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/crankshaft/hydrogen-redundant-phi.h" |
| 6 | |
| 7 | namespace v8 { |
| 8 | namespace internal { |
| 9 | |
| 10 | void HRedundantPhiEliminationPhase::Run() { |
| 11 | // Gather all phis from all blocks first. |
| 12 | const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); |
| 13 | ZoneList<HPhi*> all_phis(blocks->length(), zone()); |
| 14 | for (int i = 0; i < blocks->length(); ++i) { |
| 15 | HBasicBlock* block = blocks->at(i); |
| 16 | for (int j = 0; j < block->phis()->length(); j++) { |
| 17 | all_phis.Add(block->phis()->at(j), zone()); |
| 18 | } |
| 19 | } |
| 20 | |
| 21 | // Iteratively reduce all phis in the list. |
| 22 | ProcessPhis(&all_phis); |
| 23 | |
| 24 | #if DEBUG |
| 25 | // Make sure that we *really* removed all redundant phis. |
| 26 | for (int i = 0; i < blocks->length(); ++i) { |
| 27 | for (int j = 0; j < blocks->at(i)->phis()->length(); j++) { |
| 28 | DCHECK(blocks->at(i)->phis()->at(j)->GetRedundantReplacement() == NULL); |
| 29 | } |
| 30 | } |
| 31 | #endif |
| 32 | } |
| 33 | |
| 34 | |
| 35 | void HRedundantPhiEliminationPhase::ProcessBlock(HBasicBlock* block) { |
| 36 | ProcessPhis(block->phis()); |
| 37 | } |
| 38 | |
| 39 | |
| 40 | void HRedundantPhiEliminationPhase::ProcessPhis(const ZoneList<HPhi*>* phis) { |
| 41 | bool updated; |
| 42 | do { |
| 43 | // Iterately replace all redundant phis in the given list. |
| 44 | updated = false; |
| 45 | for (int i = 0; i < phis->length(); i++) { |
| 46 | HPhi* phi = phis->at(i); |
| 47 | if (phi->CheckFlag(HValue::kIsDead)) continue; // Already replaced. |
| 48 | |
| 49 | HValue* replacement = phi->GetRedundantReplacement(); |
| 50 | if (replacement != NULL) { |
| 51 | phi->SetFlag(HValue::kIsDead); |
| 52 | for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) { |
| 53 | HValue* value = it.value(); |
| 54 | value->SetOperandAt(it.index(), replacement); |
| 55 | // Iterate again if used in another non-dead phi. |
| 56 | updated |= value->IsPhi() && !value->CheckFlag(HValue::kIsDead); |
| 57 | } |
| 58 | phi->block()->RemovePhi(phi); |
| 59 | } |
| 60 | } |
| 61 | } while (updated); |
| 62 | } |
| 63 | |
| 64 | |
| 65 | } // namespace internal |
| 66 | } // namespace v8 |