Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +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/crankshaft/hydrogen-uint32-analysis.h" |
| 6 | |
| 7 | namespace v8 { |
| 8 | namespace internal { |
| 9 | |
| 10 | |
| 11 | static bool IsUnsignedLoad(HLoadKeyed* instr) { |
| 12 | switch (instr->elements_kind()) { |
| 13 | case UINT8_ELEMENTS: |
| 14 | case UINT16_ELEMENTS: |
| 15 | case UINT32_ELEMENTS: |
| 16 | case UINT8_CLAMPED_ELEMENTS: |
| 17 | return true; |
| 18 | default: |
| 19 | return false; |
| 20 | } |
| 21 | } |
| 22 | |
| 23 | |
| 24 | static bool IsUint32Operation(HValue* instr) { |
| 25 | return instr->IsShr() || |
| 26 | (instr->IsLoadKeyed() && IsUnsignedLoad(HLoadKeyed::cast(instr))) || |
| 27 | (instr->IsInteger32Constant() && instr->GetInteger32Constant() >= 0); |
| 28 | } |
| 29 | |
| 30 | |
| 31 | bool HUint32AnalysisPhase::IsSafeUint32Use(HValue* val, HValue* use) { |
| 32 | // Operations that operate on bits are safe. |
| 33 | if (use->IsBitwise() || use->IsShl() || use->IsSar() || use->IsShr()) { |
| 34 | return true; |
| 35 | } else if (use->IsSimulate() || use->IsArgumentsObject()) { |
| 36 | // Deoptimization has special support for uint32. |
| 37 | return true; |
| 38 | } else if (use->IsChange()) { |
| 39 | // Conversions have special support for uint32. |
| 40 | // This DCHECK guards that the conversion in question is actually |
| 41 | // implemented. Do not extend the whitelist without adding |
| 42 | // support to LChunkBuilder::DoChange(). |
| 43 | DCHECK(HChange::cast(use)->to().IsDouble() || |
| 44 | HChange::cast(use)->to().IsSmi() || |
| 45 | HChange::cast(use)->to().IsTagged()); |
| 46 | return true; |
| 47 | } else if (use->IsStoreKeyed()) { |
| 48 | HStoreKeyed* store = HStoreKeyed::cast(use); |
| 49 | if (store->is_fixed_typed_array()) { |
| 50 | // Storing a value into an external integer array is a bit level |
| 51 | // operation. |
| 52 | if (store->value() == val) { |
| 53 | // Clamping or a conversion to double should have beed inserted. |
| 54 | DCHECK(store->elements_kind() != UINT8_CLAMPED_ELEMENTS); |
| 55 | DCHECK(store->elements_kind() != FLOAT32_ELEMENTS); |
| 56 | DCHECK(store->elements_kind() != FLOAT64_ELEMENTS); |
| 57 | return true; |
| 58 | } |
| 59 | } |
| 60 | } else if (use->IsCompareNumericAndBranch()) { |
| 61 | HCompareNumericAndBranch* c = HCompareNumericAndBranch::cast(use); |
| 62 | return IsUint32Operation(c->left()) && IsUint32Operation(c->right()); |
| 63 | } |
| 64 | |
| 65 | return false; |
| 66 | } |
| 67 | |
| 68 | |
| 69 | // Iterate over all uses and verify that they are uint32 safe: either don't |
| 70 | // distinguish between int32 and uint32 due to their bitwise nature or |
| 71 | // have special support for uint32 values. |
| 72 | // Encountered phis are optimistically treated as safe uint32 uses, |
| 73 | // marked with kUint32 flag and collected in the phis_ list. A separate |
| 74 | // pass will be performed later by UnmarkUnsafePhis to clear kUint32 from |
| 75 | // phis that are not actually uint32-safe (it requires fix point iteration). |
| 76 | bool HUint32AnalysisPhase::Uint32UsesAreSafe(HValue* uint32val) { |
| 77 | bool collect_phi_uses = false; |
| 78 | for (HUseIterator it(uint32val->uses()); !it.Done(); it.Advance()) { |
| 79 | HValue* use = it.value(); |
| 80 | |
| 81 | if (use->IsPhi()) { |
| 82 | if (!use->CheckFlag(HInstruction::kUint32)) { |
| 83 | // There is a phi use of this value from a phi that is not yet |
| 84 | // collected in phis_ array. Separate pass is required. |
| 85 | collect_phi_uses = true; |
| 86 | } |
| 87 | |
| 88 | // Optimistically treat phis as uint32 safe. |
| 89 | continue; |
| 90 | } |
| 91 | |
| 92 | if (!IsSafeUint32Use(uint32val, use)) { |
| 93 | return false; |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | if (collect_phi_uses) { |
| 98 | for (HUseIterator it(uint32val->uses()); !it.Done(); it.Advance()) { |
| 99 | HValue* use = it.value(); |
| 100 | |
| 101 | // There is a phi use of this value from a phi that is not yet |
| 102 | // collected in phis_ array. Separate pass is required. |
| 103 | if (use->IsPhi() && !use->CheckFlag(HInstruction::kUint32)) { |
| 104 | use->SetFlag(HInstruction::kUint32); |
| 105 | phis_.Add(HPhi::cast(use), zone()); |
| 106 | } |
| 107 | } |
| 108 | } |
| 109 | |
| 110 | return true; |
| 111 | } |
| 112 | |
| 113 | |
| 114 | // Check if all operands to the given phi are marked with kUint32 flag. |
| 115 | bool HUint32AnalysisPhase::CheckPhiOperands(HPhi* phi) { |
| 116 | if (!phi->CheckFlag(HInstruction::kUint32)) { |
| 117 | // This phi is not uint32 safe. No need to check operands. |
| 118 | return false; |
| 119 | } |
| 120 | |
| 121 | for (int j = 0; j < phi->OperandCount(); j++) { |
| 122 | HValue* operand = phi->OperandAt(j); |
| 123 | if (!operand->CheckFlag(HInstruction::kUint32)) { |
| 124 | // Lazily mark constants that fit into uint32 range with kUint32 flag. |
| 125 | if (operand->IsInteger32Constant() && |
| 126 | operand->GetInteger32Constant() >= 0) { |
| 127 | operand->SetFlag(HInstruction::kUint32); |
| 128 | continue; |
| 129 | } |
| 130 | |
| 131 | // This phi is not safe, some operands are not uint32 values. |
| 132 | return false; |
| 133 | } |
| 134 | } |
| 135 | |
| 136 | return true; |
| 137 | } |
| 138 | |
| 139 | |
| 140 | // Remove kUint32 flag from the phi itself and its operands. If any operand |
| 141 | // was a phi marked with kUint32 place it into a worklist for |
| 142 | // transitive clearing of kUint32 flag. |
| 143 | void HUint32AnalysisPhase::UnmarkPhi(HPhi* phi, ZoneList<HPhi*>* worklist) { |
| 144 | phi->ClearFlag(HInstruction::kUint32); |
| 145 | for (int j = 0; j < phi->OperandCount(); j++) { |
| 146 | HValue* operand = phi->OperandAt(j); |
| 147 | if (operand->CheckFlag(HInstruction::kUint32)) { |
| 148 | operand->ClearFlag(HInstruction::kUint32); |
| 149 | if (operand->IsPhi()) { |
| 150 | worklist->Add(HPhi::cast(operand), zone()); |
| 151 | } |
| 152 | } |
| 153 | } |
| 154 | } |
| 155 | |
| 156 | |
| 157 | void HUint32AnalysisPhase::UnmarkUnsafePhis() { |
| 158 | // No phis were collected. Nothing to do. |
| 159 | if (phis_.length() == 0) return; |
| 160 | |
| 161 | // Worklist used to transitively clear kUint32 from phis that |
| 162 | // are used as arguments to other phis. |
| 163 | ZoneList<HPhi*> worklist(phis_.length(), zone()); |
| 164 | |
| 165 | // Phi can be used as a uint32 value if and only if |
| 166 | // all its operands are uint32 values and all its |
| 167 | // uses are uint32 safe. |
| 168 | |
| 169 | // Iterate over collected phis and unmark those that |
| 170 | // are unsafe. When unmarking phi unmark its operands |
| 171 | // and add it to the worklist if it is a phi as well. |
| 172 | // Phis that are still marked as safe are shifted down |
| 173 | // so that all safe phis form a prefix of the phis_ array. |
| 174 | int phi_count = 0; |
| 175 | for (int i = 0; i < phis_.length(); i++) { |
| 176 | HPhi* phi = phis_[i]; |
| 177 | |
| 178 | if (CheckPhiOperands(phi) && Uint32UsesAreSafe(phi)) { |
| 179 | phis_[phi_count++] = phi; |
| 180 | } else { |
| 181 | UnmarkPhi(phi, &worklist); |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | // Now phis array contains only those phis that have safe |
| 186 | // non-phi uses. Start transitively clearing kUint32 flag |
| 187 | // from phi operands of discovered non-safe phis until |
| 188 | // only safe phis are left. |
| 189 | while (!worklist.is_empty()) { |
| 190 | while (!worklist.is_empty()) { |
| 191 | HPhi* phi = worklist.RemoveLast(); |
| 192 | UnmarkPhi(phi, &worklist); |
| 193 | } |
| 194 | |
| 195 | // Check if any operands to safe phis were unmarked |
| 196 | // turning a safe phi into unsafe. The same value |
| 197 | // can flow into several phis. |
| 198 | int new_phi_count = 0; |
| 199 | for (int i = 0; i < phi_count; i++) { |
| 200 | HPhi* phi = phis_[i]; |
| 201 | |
| 202 | if (CheckPhiOperands(phi)) { |
| 203 | phis_[new_phi_count++] = phi; |
| 204 | } else { |
| 205 | UnmarkPhi(phi, &worklist); |
| 206 | } |
| 207 | } |
| 208 | phi_count = new_phi_count; |
| 209 | } |
| 210 | } |
| 211 | |
| 212 | |
| 213 | void HUint32AnalysisPhase::Run() { |
| 214 | if (!graph()->has_uint32_instructions()) return; |
| 215 | |
| 216 | ZoneList<HInstruction*>* uint32_instructions = graph()->uint32_instructions(); |
| 217 | for (int i = 0; i < uint32_instructions->length(); ++i) { |
| 218 | // Analyze instruction and mark it with kUint32 if all |
| 219 | // its uses are uint32 safe. |
| 220 | HInstruction* current = uint32_instructions->at(i); |
| 221 | if (current->IsLinked() && |
| 222 | current->representation().IsInteger32() && |
| 223 | Uint32UsesAreSafe(current)) { |
| 224 | current->SetFlag(HInstruction::kUint32); |
| 225 | } |
| 226 | } |
| 227 | |
| 228 | // Some phis might have been optimistically marked with kUint32 flag. |
| 229 | // Remove this flag from those phis that are unsafe and propagate |
| 230 | // this information transitively potentially clearing kUint32 flag |
| 231 | // from some non-phi operations that are used as operands to unsafe phis. |
| 232 | UnmarkUnsafePhis(); |
| 233 | } |
| 234 | |
| 235 | |
| 236 | } // namespace internal |
| 237 | } // namespace v8 |