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-representation-changes.h" 29 30 namespace v8 { 31 namespace internal { 32 33 void HRepresentationChangesPhase::InsertRepresentationChangeForUse( 34 HValue* value, HValue* use_value, int use_index, Representation to) { 35 // Insert the representation change right before its use. For phi-uses we 36 // insert at the end of the corresponding predecessor. 37 HInstruction* next = NULL; 38 if (use_value->IsPhi()) { 39 next = use_value->block()->predecessors()->at(use_index)->end(); 40 } else { 41 next = HInstruction::cast(use_value); 42 } 43 // For constants we try to make the representation change at compile 44 // time. When a representation change is not possible without loss of 45 // information we treat constants like normal instructions and insert the 46 // change instructions for them. 47 HInstruction* new_value = NULL; 48 bool is_truncating_to_smi = use_value->CheckFlag(HValue::kTruncatingToSmi); 49 bool is_truncating_to_int = use_value->CheckFlag(HValue::kTruncatingToInt32); 50 if (value->IsConstant()) { 51 HConstant* constant = HConstant::cast(value); 52 // Try to create a new copy of the constant with the new representation. 53 if (is_truncating_to_int && to.IsInteger32()) { 54 Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone()); 55 if (res.has_value) new_value = res.value; 56 } else { 57 new_value = constant->CopyToRepresentation(to, graph()->zone()); 58 } 59 } 60 61 if (new_value == NULL) { 62 new_value = new(graph()->zone()) HChange( 63 value, to, is_truncating_to_smi, is_truncating_to_int); 64 } 65 66 new_value->InsertBefore(next); 67 use_value->SetOperandAt(use_index, new_value); 68 } 69 70 71 void HRepresentationChangesPhase::InsertRepresentationChangesForValue( 72 HValue* value) { 73 Representation r = value->representation(); 74 if (r.IsNone()) return; 75 if (value->HasNoUses()) return; 76 77 for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) { 78 HValue* use_value = it.value(); 79 int use_index = it.index(); 80 Representation req = use_value->RequiredInputRepresentation(use_index); 81 if (req.IsNone() || req.Equals(r)) continue; 82 InsertRepresentationChangeForUse(value, use_value, use_index, req); 83 } 84 if (value->HasNoUses()) { 85 ASSERT(value->IsConstant()); 86 value->DeleteAndReplaceWith(NULL); 87 } 88 89 // The only purpose of a HForceRepresentation is to represent the value 90 // after the (possible) HChange instruction. We make it disappear. 91 if (value->IsForceRepresentation()) { 92 value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value()); 93 } 94 } 95 96 97 void HRepresentationChangesPhase::Run() { 98 // Compute truncation flag for phis: Initially assume that all 99 // int32-phis allow truncation and iteratively remove the ones that 100 // are used in an operation that does not allow a truncating 101 // conversion. 102 ZoneList<HPhi*> worklist(8, zone()); 103 104 const ZoneList<HPhi*>* phi_list(graph()->phi_list()); 105 for (int i = 0; i < phi_list->length(); i++) { 106 HPhi* phi = phi_list->at(i); 107 if (phi->representation().IsInteger32()) { 108 phi->SetFlag(HValue::kTruncatingToInt32); 109 } else if (phi->representation().IsSmi()) { 110 phi->SetFlag(HValue::kTruncatingToSmi); 111 } 112 } 113 114 for (int i = 0; i < phi_list->length(); i++) { 115 HPhi* phi = phi_list->at(i); 116 for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) { 117 // If a Phi is used as a non-truncating int32 or as a double, 118 // clear its "truncating" flag. 119 HValue* use = it.value(); 120 Representation input_representation = 121 use->RequiredInputRepresentation(it.index()); 122 if ((phi->representation().IsInteger32() && 123 !(input_representation.IsInteger32() && 124 use->CheckFlag(HValue::kTruncatingToInt32))) || 125 (phi->representation().IsSmi() && 126 !(input_representation.IsSmi() && 127 use->CheckFlag(HValue::kTruncatingToSmi)))) { 128 if (FLAG_trace_representation) { 129 PrintF("#%d Phi is not truncating because of #%d %s\n", 130 phi->id(), it.value()->id(), it.value()->Mnemonic()); 131 } 132 phi->ClearFlag(HValue::kTruncatingToInt32); 133 phi->ClearFlag(HValue::kTruncatingToSmi); 134 worklist.Add(phi, zone()); 135 break; 136 } 137 } 138 } 139 140 while (!worklist.is_empty()) { 141 HPhi* current = worklist.RemoveLast(); 142 for (int i = 0; i < current->OperandCount(); ++i) { 143 HValue* input = current->OperandAt(i); 144 if (input->IsPhi() && 145 ((input->representation().IsInteger32() && 146 input->CheckFlag(HValue::kTruncatingToInt32)) || 147 (input->representation().IsSmi() && 148 input->CheckFlag(HValue::kTruncatingToSmi)))) { 149 if (FLAG_trace_representation) { 150 PrintF("#%d Phi is not truncating because of #%d %s\n", 151 input->id(), current->id(), current->Mnemonic()); 152 } 153 input->ClearFlag(HValue::kTruncatingToInt32); 154 input->ClearFlag(HValue::kTruncatingToSmi); 155 worklist.Add(HPhi::cast(input), zone()); 156 } 157 } 158 } 159 160 const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); 161 for (int i = 0; i < blocks->length(); ++i) { 162 // Process phi instructions first. 163 const HBasicBlock* block(blocks->at(i)); 164 const ZoneList<HPhi*>* phis = block->phis(); 165 for (int j = 0; j < phis->length(); j++) { 166 InsertRepresentationChangesForValue(phis->at(j)); 167 } 168 169 // Process normal instructions. 170 for (HInstruction* current = block->first(); current != NULL; ) { 171 HInstruction* next = current->next(); 172 InsertRepresentationChangesForValue(current); 173 current = next; 174 } 175 } 176 } 177 178 } } // namespace v8::internal 179
