1 // Copyright 2013 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #include "hydrogen-canonicalize.h" 29 #include "hydrogen-redundant-phi.h" 30 31 namespace v8 { 32 namespace internal { 33 34 void HCanonicalizePhase::Run() { 35 const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); 36 // Before removing no-op instructions, save their semantic value. 37 // We must be careful not to set the flag unnecessarily, because GVN 38 // cannot identify two instructions when their flag value differs. 39 for (int i = 0; i < blocks->length(); ++i) { 40 for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) { 41 HInstruction* instr = it.Current(); 42 if (instr->IsArithmeticBinaryOperation()) { 43 if (instr->representation().IsInteger32()) { 44 if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( 45 HInstruction::kTruncatingToInt32)) { 46 instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32); 47 } 48 } else if (instr->representation().IsSmi()) { 49 if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( 50 HInstruction::kTruncatingToSmi)) { 51 instr->SetFlag(HInstruction::kAllUsesTruncatingToSmi); 52 } else if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( 53 HInstruction::kTruncatingToInt32)) { 54 // Avoid redundant minus zero check 55 instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32); 56 } 57 } 58 } 59 } 60 } 61 62 // Perform actual Canonicalization pass. 63 HRedundantPhiEliminationPhase redundant_phi_eliminator(graph()); 64 for (int i = 0; i < blocks->length(); ++i) { 65 // Eliminate redundant phis in the block first; changes to their inputs 66 // might have made them redundant, and eliminating them creates more 67 // opportunities for constant folding and strength reduction. 68 redundant_phi_eliminator.ProcessBlock(blocks->at(i)); 69 // Now canonicalize each instruction. 70 for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) { 71 HInstruction* instr = it.Current(); 72 HValue* value = instr->Canonicalize(); 73 if (value != instr) instr->DeleteAndReplaceWith(value); 74 } 75 } 76 } 77 78 } } // namespace v8::internal 79
