| // Copyright 2013 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/hydrogen-uint32-analysis.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| |
| static bool IsUnsignedLoad(HLoadKeyed* instr) { |
| switch (instr->elements_kind()) { |
| case EXTERNAL_UINT8_ELEMENTS: |
| case EXTERNAL_UINT16_ELEMENTS: |
| case EXTERNAL_UINT32_ELEMENTS: |
| case EXTERNAL_UINT8_CLAMPED_ELEMENTS: |
| case UINT8_ELEMENTS: |
| case UINT16_ELEMENTS: |
| case UINT32_ELEMENTS: |
| case UINT8_CLAMPED_ELEMENTS: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| |
| static bool IsUint32Operation(HValue* instr) { |
| return instr->IsShr() || |
| (instr->IsLoadKeyed() && IsUnsignedLoad(HLoadKeyed::cast(instr))) || |
| (instr->IsInteger32Constant() && instr->GetInteger32Constant() >= 0); |
| } |
| |
| |
| bool HUint32AnalysisPhase::IsSafeUint32Use(HValue* val, HValue* use) { |
| // Operations that operate on bits are safe. |
| if (use->IsBitwise() || use->IsShl() || use->IsSar() || use->IsShr()) { |
| return true; |
| } else if (use->IsSimulate()) { |
| // Deoptimization has special support for uint32. |
| return true; |
| } else if (use->IsChange()) { |
| // Conversions have special support for uint32. |
| // This DCHECK guards that the conversion in question is actually |
| // implemented. Do not extend the whitelist without adding |
| // support to LChunkBuilder::DoChange(). |
| DCHECK(HChange::cast(use)->to().IsDouble() || |
| HChange::cast(use)->to().IsSmi() || |
| HChange::cast(use)->to().IsTagged()); |
| return true; |
| } else if (use->IsStoreKeyed()) { |
| HStoreKeyed* store = HStoreKeyed::cast(use); |
| if (store->is_external()) { |
| // Storing a value into an external integer array is a bit level |
| // operation. |
| if (store->value() == val) { |
| // Clamping or a conversion to double should have beed inserted. |
| DCHECK(store->elements_kind() != EXTERNAL_UINT8_CLAMPED_ELEMENTS); |
| DCHECK(store->elements_kind() != EXTERNAL_FLOAT32_ELEMENTS); |
| DCHECK(store->elements_kind() != EXTERNAL_FLOAT64_ELEMENTS); |
| return true; |
| } |
| } |
| } else if (use->IsCompareNumericAndBranch()) { |
| HCompareNumericAndBranch* c = HCompareNumericAndBranch::cast(use); |
| return IsUint32Operation(c->left()) && IsUint32Operation(c->right()); |
| } |
| |
| return false; |
| } |
| |
| |
| // Iterate over all uses and verify that they are uint32 safe: either don't |
| // distinguish between int32 and uint32 due to their bitwise nature or |
| // have special support for uint32 values. |
| // Encountered phis are optimistically treated as safe uint32 uses, |
| // marked with kUint32 flag and collected in the phis_ list. A separate |
| // pass will be performed later by UnmarkUnsafePhis to clear kUint32 from |
| // phis that are not actually uint32-safe (it requires fix point iteration). |
| bool HUint32AnalysisPhase::Uint32UsesAreSafe(HValue* uint32val) { |
| bool collect_phi_uses = false; |
| for (HUseIterator it(uint32val->uses()); !it.Done(); it.Advance()) { |
| HValue* use = it.value(); |
| |
| if (use->IsPhi()) { |
| if (!use->CheckFlag(HInstruction::kUint32)) { |
| // There is a phi use of this value from a phi that is not yet |
| // collected in phis_ array. Separate pass is required. |
| collect_phi_uses = true; |
| } |
| |
| // Optimistically treat phis as uint32 safe. |
| continue; |
| } |
| |
| if (!IsSafeUint32Use(uint32val, use)) { |
| return false; |
| } |
| } |
| |
| if (collect_phi_uses) { |
| for (HUseIterator it(uint32val->uses()); !it.Done(); it.Advance()) { |
| HValue* use = it.value(); |
| |
| // There is a phi use of this value from a phi that is not yet |
| // collected in phis_ array. Separate pass is required. |
| if (use->IsPhi() && !use->CheckFlag(HInstruction::kUint32)) { |
| use->SetFlag(HInstruction::kUint32); |
| phis_.Add(HPhi::cast(use), zone()); |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| // Check if all operands to the given phi are marked with kUint32 flag. |
| bool HUint32AnalysisPhase::CheckPhiOperands(HPhi* phi) { |
| if (!phi->CheckFlag(HInstruction::kUint32)) { |
| // This phi is not uint32 safe. No need to check operands. |
| return false; |
| } |
| |
| for (int j = 0; j < phi->OperandCount(); j++) { |
| HValue* operand = phi->OperandAt(j); |
| if (!operand->CheckFlag(HInstruction::kUint32)) { |
| // Lazily mark constants that fit into uint32 range with kUint32 flag. |
| if (operand->IsInteger32Constant() && |
| operand->GetInteger32Constant() >= 0) { |
| operand->SetFlag(HInstruction::kUint32); |
| continue; |
| } |
| |
| // This phi is not safe, some operands are not uint32 values. |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| // Remove kUint32 flag from the phi itself and its operands. If any operand |
| // was a phi marked with kUint32 place it into a worklist for |
| // transitive clearing of kUint32 flag. |
| void HUint32AnalysisPhase::UnmarkPhi(HPhi* phi, ZoneList<HPhi*>* worklist) { |
| phi->ClearFlag(HInstruction::kUint32); |
| for (int j = 0; j < phi->OperandCount(); j++) { |
| HValue* operand = phi->OperandAt(j); |
| if (operand->CheckFlag(HInstruction::kUint32)) { |
| operand->ClearFlag(HInstruction::kUint32); |
| if (operand->IsPhi()) { |
| worklist->Add(HPhi::cast(operand), zone()); |
| } |
| } |
| } |
| } |
| |
| |
| void HUint32AnalysisPhase::UnmarkUnsafePhis() { |
| // No phis were collected. Nothing to do. |
| if (phis_.length() == 0) return; |
| |
| // Worklist used to transitively clear kUint32 from phis that |
| // are used as arguments to other phis. |
| ZoneList<HPhi*> worklist(phis_.length(), zone()); |
| |
| // Phi can be used as a uint32 value if and only if |
| // all its operands are uint32 values and all its |
| // uses are uint32 safe. |
| |
| // Iterate over collected phis and unmark those that |
| // are unsafe. When unmarking phi unmark its operands |
| // and add it to the worklist if it is a phi as well. |
| // Phis that are still marked as safe are shifted down |
| // so that all safe phis form a prefix of the phis_ array. |
| int phi_count = 0; |
| for (int i = 0; i < phis_.length(); i++) { |
| HPhi* phi = phis_[i]; |
| |
| if (CheckPhiOperands(phi) && Uint32UsesAreSafe(phi)) { |
| phis_[phi_count++] = phi; |
| } else { |
| UnmarkPhi(phi, &worklist); |
| } |
| } |
| |
| // Now phis array contains only those phis that have safe |
| // non-phi uses. Start transitively clearing kUint32 flag |
| // from phi operands of discovered non-safe phis until |
| // only safe phis are left. |
| while (!worklist.is_empty()) { |
| while (!worklist.is_empty()) { |
| HPhi* phi = worklist.RemoveLast(); |
| UnmarkPhi(phi, &worklist); |
| } |
| |
| // Check if any operands to safe phis were unmarked |
| // turning a safe phi into unsafe. The same value |
| // can flow into several phis. |
| int new_phi_count = 0; |
| for (int i = 0; i < phi_count; i++) { |
| HPhi* phi = phis_[i]; |
| |
| if (CheckPhiOperands(phi)) { |
| phis_[new_phi_count++] = phi; |
| } else { |
| UnmarkPhi(phi, &worklist); |
| } |
| } |
| phi_count = new_phi_count; |
| } |
| } |
| |
| |
| void HUint32AnalysisPhase::Run() { |
| if (!graph()->has_uint32_instructions()) return; |
| |
| ZoneList<HInstruction*>* uint32_instructions = graph()->uint32_instructions(); |
| for (int i = 0; i < uint32_instructions->length(); ++i) { |
| // Analyze instruction and mark it with kUint32 if all |
| // its uses are uint32 safe. |
| HInstruction* current = uint32_instructions->at(i); |
| if (current->IsLinked() && |
| current->representation().IsInteger32() && |
| Uint32UsesAreSafe(current)) { |
| current->SetFlag(HInstruction::kUint32); |
| } |
| } |
| |
| // Some phis might have been optimistically marked with kUint32 flag. |
| // Remove this flag from those phis that are unsafe and propagate |
| // this information transitively potentially clearing kUint32 flag |
| // from some non-phi operations that are used as operands to unsafe phis. |
| UnmarkUnsafePhis(); |
| } |
| |
| |
| } } // namespace v8::internal |