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 if (use_value->operand_position(use_index) != RelocInfo::kNoPosition) { 65 new_value->set_position(use_value->operand_position(use_index)); 66 } else { 67 ASSERT(!FLAG_emit_opt_code_positions || !graph()->info()->IsOptimizing()); 68 } 69 } 70 71 new_value->InsertBefore(next); 72 use_value->SetOperandAt(use_index, new_value); 73 } 74 75 76 void HRepresentationChangesPhase::InsertRepresentationChangesForValue( 77 HValue* value) { 78 Representation r = value->representation(); 79 if (r.IsNone()) return; 80 if (value->HasNoUses()) return; 81 82 for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) { 83 HValue* use_value = it.value(); 84 int use_index = it.index(); 85 Representation req = use_value->RequiredInputRepresentation(use_index); 86 if (req.IsNone() || req.Equals(r)) continue; 87 InsertRepresentationChangeForUse(value, use_value, use_index, req); 88 } 89 if (value->HasNoUses()) { 90 ASSERT(value->IsConstant()); 91 value->DeleteAndReplaceWith(NULL); 92 } 93 94 // The only purpose of a HForceRepresentation is to represent the value 95 // after the (possible) HChange instruction. We make it disappear. 96 if (value->IsForceRepresentation()) { 97 value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value()); 98 } 99 } 100 101 102 void HRepresentationChangesPhase::Run() { 103 // Compute truncation flag for phis: Initially assume that all 104 // int32-phis allow truncation and iteratively remove the ones that 105 // are used in an operation that does not allow a truncating 106 // conversion. 107 ZoneList<HPhi*> int_worklist(8, zone()); 108 ZoneList<HPhi*> smi_worklist(8, zone()); 109 110 const ZoneList<HPhi*>* phi_list(graph()->phi_list()); 111 for (int i = 0; i < phi_list->length(); i++) { 112 HPhi* phi = phi_list->at(i); 113 if (phi->representation().IsInteger32()) { 114 phi->SetFlag(HValue::kTruncatingToInt32); 115 } else if (phi->representation().IsSmi()) { 116 phi->SetFlag(HValue::kTruncatingToSmi); 117 phi->SetFlag(HValue::kTruncatingToInt32); 118 } 119 } 120 121 for (int i = 0; i < phi_list->length(); i++) { 122 HPhi* phi = phi_list->at(i); 123 HValue* value = NULL; 124 if (phi->representation().IsSmiOrInteger32() && 125 !phi->CheckUsesForFlag(HValue::kTruncatingToInt32, &value)) { 126 int_worklist.Add(phi, zone()); 127 phi->ClearFlag(HValue::kTruncatingToInt32); 128 if (FLAG_trace_representation) { 129 PrintF("#%d Phi is not truncating Int32 because of #%d %s\n", 130 phi->id(), value->id(), value->Mnemonic()); 131 } 132 } 133 134 if (phi->representation().IsSmi() && 135 !phi->CheckUsesForFlag(HValue::kTruncatingToSmi, &value)) { 136 smi_worklist.Add(phi, zone()); 137 phi->ClearFlag(HValue::kTruncatingToSmi); 138 if (FLAG_trace_representation) { 139 PrintF("#%d Phi is not truncating Smi because of #%d %s\n", 140 phi->id(), value->id(), value->Mnemonic()); 141 } 142 } 143 } 144 145 while (!int_worklist.is_empty()) { 146 HPhi* current = int_worklist.RemoveLast(); 147 for (int i = 0; i < current->OperandCount(); ++i) { 148 HValue* input = current->OperandAt(i); 149 if (input->IsPhi() && 150 input->representation().IsSmiOrInteger32() && 151 input->CheckFlag(HValue::kTruncatingToInt32)) { 152 if (FLAG_trace_representation) { 153 PrintF("#%d Phi is not truncating Int32 because of #%d %s\n", 154 input->id(), current->id(), current->Mnemonic()); 155 } 156 input->ClearFlag(HValue::kTruncatingToInt32); 157 int_worklist.Add(HPhi::cast(input), zone()); 158 } 159 } 160 } 161 162 while (!smi_worklist.is_empty()) { 163 HPhi* current = smi_worklist.RemoveLast(); 164 for (int i = 0; i < current->OperandCount(); ++i) { 165 HValue* input = current->OperandAt(i); 166 if (input->IsPhi() && 167 input->representation().IsSmi() && 168 input->CheckFlag(HValue::kTruncatingToSmi)) { 169 if (FLAG_trace_representation) { 170 PrintF("#%d Phi is not truncating Smi because of #%d %s\n", 171 input->id(), current->id(), current->Mnemonic()); 172 } 173 input->ClearFlag(HValue::kTruncatingToSmi); 174 smi_worklist.Add(HPhi::cast(input), zone()); 175 } 176 } 177 } 178 179 const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); 180 for (int i = 0; i < blocks->length(); ++i) { 181 // Process phi instructions first. 182 const HBasicBlock* block(blocks->at(i)); 183 const ZoneList<HPhi*>* phis = block->phis(); 184 for (int j = 0; j < phis->length(); j++) { 185 InsertRepresentationChangesForValue(phis->at(j)); 186 } 187 188 // Process normal instructions. 189 for (HInstruction* current = block->first(); current != NULL; ) { 190 HInstruction* next = current->next(); 191 InsertRepresentationChangesForValue(current); 192 current = next; 193 } 194 } 195 } 196 197 } } // namespace v8::internal 198
