Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +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/hydrogen-canonicalize.h" |
| 6 | #include "src/hydrogen-redundant-phi.h" |
| 7 | |
| 8 | namespace v8 { |
| 9 | namespace internal { |
| 10 | |
| 11 | void HCanonicalizePhase::Run() { |
| 12 | const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); |
| 13 | // Before removing no-op instructions, save their semantic value. |
| 14 | // We must be careful not to set the flag unnecessarily, because GVN |
| 15 | // cannot identify two instructions when their flag value differs. |
| 16 | for (int i = 0; i < blocks->length(); ++i) { |
| 17 | for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) { |
| 18 | HInstruction* instr = it.Current(); |
| 19 | if (instr->IsArithmeticBinaryOperation()) { |
| 20 | if (instr->representation().IsInteger32()) { |
| 21 | if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( |
| 22 | HInstruction::kTruncatingToInt32)) { |
| 23 | instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32); |
| 24 | } |
| 25 | } else if (instr->representation().IsSmi()) { |
| 26 | if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( |
| 27 | HInstruction::kTruncatingToSmi)) { |
| 28 | instr->SetFlag(HInstruction::kAllUsesTruncatingToSmi); |
| 29 | } else if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( |
| 30 | HInstruction::kTruncatingToInt32)) { |
| 31 | // Avoid redundant minus zero check |
| 32 | instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32); |
| 33 | } |
| 34 | } |
| 35 | } |
| 36 | } |
| 37 | } |
| 38 | |
| 39 | // Perform actual Canonicalization pass. |
| 40 | HRedundantPhiEliminationPhase redundant_phi_eliminator(graph()); |
| 41 | for (int i = 0; i < blocks->length(); ++i) { |
| 42 | // Eliminate redundant phis in the block first; changes to their inputs |
| 43 | // might have made them redundant, and eliminating them creates more |
| 44 | // opportunities for constant folding and strength reduction. |
| 45 | redundant_phi_eliminator.ProcessBlock(blocks->at(i)); |
| 46 | // Now canonicalize each instruction. |
| 47 | for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) { |
| 48 | HInstruction* instr = it.Current(); |
| 49 | HValue* value = instr->Canonicalize(); |
| 50 | if (value != instr) instr->DeleteAndReplaceWith(value); |
| 51 | } |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | } } // namespace v8::internal |