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 56
