| /* |
| * Copyright (C) 2015 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "load_store_elimination.h" |
| |
| #include "base/array_ref.h" |
| #include "base/scoped_arena_allocator.h" |
| #include "base/scoped_arena_containers.h" |
| #include "escape.h" |
| #include "load_store_analysis.h" |
| #include "side_effects_analysis.h" |
| |
| #include <iostream> |
| |
| namespace art { |
| |
| // An unknown heap value. Loads with such a value in the heap location cannot be eliminated. |
| // A heap location can be set to kUnknownHeapValue when: |
| // - initially set a value. |
| // - killed due to aliasing, merging, invocation, or loop side effects. |
| static HInstruction* const kUnknownHeapValue = |
| reinterpret_cast<HInstruction*>(static_cast<uintptr_t>(-1)); |
| |
| // Default heap value after an allocation. |
| // A heap location can be set to that value right after an allocation. |
| static HInstruction* const kDefaultHeapValue = |
| reinterpret_cast<HInstruction*>(static_cast<uintptr_t>(-2)); |
| |
| // Use HGraphDelegateVisitor for which all VisitInvokeXXX() delegate to VisitInvoke(). |
| class LSEVisitor : public HGraphDelegateVisitor { |
| public: |
| LSEVisitor(HGraph* graph, |
| const HeapLocationCollector& heap_locations_collector, |
| const SideEffectsAnalysis& side_effects, |
| OptimizingCompilerStats* stats) |
| : HGraphDelegateVisitor(graph, stats), |
| heap_location_collector_(heap_locations_collector), |
| side_effects_(side_effects), |
| allocator_(graph->GetArenaStack()), |
| heap_values_for_(graph->GetBlocks().size(), |
| ScopedArenaVector<HInstruction*>(heap_locations_collector. |
| GetNumberOfHeapLocations(), |
| kUnknownHeapValue, |
| allocator_.Adapter(kArenaAllocLSE)), |
| allocator_.Adapter(kArenaAllocLSE)), |
| removed_loads_(allocator_.Adapter(kArenaAllocLSE)), |
| substitute_instructions_for_loads_(allocator_.Adapter(kArenaAllocLSE)), |
| possibly_removed_stores_(allocator_.Adapter(kArenaAllocLSE)), |
| singleton_new_instances_(allocator_.Adapter(kArenaAllocLSE)), |
| singleton_new_arrays_(allocator_.Adapter(kArenaAllocLSE)) { |
| } |
| |
| void VisitBasicBlock(HBasicBlock* block) OVERRIDE { |
| // Populate the heap_values array for this block. |
| // TODO: try to reuse the heap_values array from one predecessor if possible. |
| if (block->IsLoopHeader()) { |
| HandleLoopSideEffects(block); |
| } else { |
| MergePredecessorValues(block); |
| } |
| HGraphVisitor::VisitBasicBlock(block); |
| } |
| |
| // Remove recorded instructions that should be eliminated. |
| void RemoveInstructions() { |
| size_t size = removed_loads_.size(); |
| DCHECK_EQ(size, substitute_instructions_for_loads_.size()); |
| for (size_t i = 0; i < size; i++) { |
| HInstruction* load = removed_loads_[i]; |
| DCHECK(load != nullptr); |
| DCHECK(load->IsInstanceFieldGet() || |
| load->IsStaticFieldGet() || |
| load->IsArrayGet() || |
| load->IsVecLoad()); |
| HInstruction* substitute = substitute_instructions_for_loads_[i]; |
| DCHECK(substitute != nullptr); |
| // Keep tracing substitute till one that's not removed. |
| HInstruction* sub_sub = FindSubstitute(substitute); |
| while (sub_sub != substitute) { |
| substitute = sub_sub; |
| sub_sub = FindSubstitute(substitute); |
| } |
| load->ReplaceWith(substitute); |
| load->GetBlock()->RemoveInstruction(load); |
| } |
| |
| // At this point, stores in possibly_removed_stores_ can be safely removed. |
| for (HInstruction* store : possibly_removed_stores_) { |
| DCHECK(store->IsInstanceFieldSet() || |
| store->IsStaticFieldSet() || |
| store->IsArraySet() || |
| store->IsVecStore()); |
| store->GetBlock()->RemoveInstruction(store); |
| } |
| |
| // Eliminate singleton-classified instructions: |
| // * - Constructor fences (they never escape this thread). |
| // * - Allocations (if they are unused). |
| for (HInstruction* new_instance : singleton_new_instances_) { |
| size_t removed = HConstructorFence::RemoveConstructorFences(new_instance); |
| MaybeRecordStat(stats_, |
| MethodCompilationStat::kConstructorFenceRemovedLSE, |
| removed); |
| |
| if (!new_instance->HasNonEnvironmentUses()) { |
| new_instance->RemoveEnvironmentUsers(); |
| new_instance->GetBlock()->RemoveInstruction(new_instance); |
| } |
| } |
| for (HInstruction* new_array : singleton_new_arrays_) { |
| size_t removed = HConstructorFence::RemoveConstructorFences(new_array); |
| MaybeRecordStat(stats_, |
| MethodCompilationStat::kConstructorFenceRemovedLSE, |
| removed); |
| |
| if (!new_array->HasNonEnvironmentUses()) { |
| new_array->RemoveEnvironmentUsers(); |
| new_array->GetBlock()->RemoveInstruction(new_array); |
| } |
| } |
| } |
| |
| private: |
| // If heap_values[index] is an instance field store, need to keep the store. |
| // This is necessary if a heap value is killed due to merging, or loop side |
| // effects (which is essentially merging also), since a load later from the |
| // location won't be eliminated. |
| void KeepIfIsStore(HInstruction* heap_value) { |
| if (heap_value == kDefaultHeapValue || |
| heap_value == kUnknownHeapValue || |
| !(heap_value->IsInstanceFieldSet() || |
| heap_value->IsArraySet() || |
| heap_value->IsVecStore())) { |
| return; |
| } |
| auto idx = std::find(possibly_removed_stores_.begin(), |
| possibly_removed_stores_.end(), heap_value); |
| if (idx != possibly_removed_stores_.end()) { |
| // Make sure the store is kept. |
| possibly_removed_stores_.erase(idx); |
| } |
| } |
| |
| void HandleLoopSideEffects(HBasicBlock* block) { |
| DCHECK(block->IsLoopHeader()); |
| int block_id = block->GetBlockId(); |
| ScopedArenaVector<HInstruction*>& heap_values = heap_values_for_[block_id]; |
| |
| // Don't eliminate loads in irreducible loops. This is safe for singletons, because |
| // they are always used by the non-eliminated loop-phi. |
| if (block->GetLoopInformation()->IsIrreducible()) { |
| if (kIsDebugBuild) { |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| DCHECK_EQ(heap_values[i], kUnknownHeapValue); |
| } |
| } |
| return; |
| } |
| |
| HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader(); |
| ScopedArenaVector<HInstruction*>& pre_header_heap_values = |
| heap_values_for_[pre_header->GetBlockId()]; |
| |
| // Inherit the values from pre-header. |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| heap_values[i] = pre_header_heap_values[i]; |
| } |
| |
| // We do a single pass in reverse post order. For loops, use the side effects as a hint |
| // to see if the heap values should be killed. |
| if (side_effects_.GetLoopEffects(block).DoesAnyWrite()) { |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| HeapLocation* location = heap_location_collector_.GetHeapLocation(i); |
| ReferenceInfo* ref_info = location->GetReferenceInfo(); |
| if (ref_info->IsSingletonAndRemovable() && |
| !location->IsValueKilledByLoopSideEffects()) { |
| // A removable singleton's field that's not stored into inside a loop is |
| // invariant throughout the loop. Nothing to do. |
| } else { |
| // heap value is killed by loop side effects (stored into directly, or |
| // due to aliasing). Or the heap value may be needed after method return |
| // or deoptimization. |
| KeepIfIsStore(pre_header_heap_values[i]); |
| heap_values[i] = kUnknownHeapValue; |
| } |
| } |
| } |
| } |
| |
| void MergePredecessorValues(HBasicBlock* block) { |
| ArrayRef<HBasicBlock* const> predecessors(block->GetPredecessors()); |
| if (predecessors.size() == 0) { |
| return; |
| } |
| |
| ScopedArenaVector<HInstruction*>& heap_values = heap_values_for_[block->GetBlockId()]; |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| HInstruction* merged_value = nullptr; |
| // Whether merged_value is a result that's merged from all predecessors. |
| bool from_all_predecessors = true; |
| ReferenceInfo* ref_info = heap_location_collector_.GetHeapLocation(i)->GetReferenceInfo(); |
| HInstruction* singleton_ref = nullptr; |
| if (ref_info->IsSingleton()) { |
| // We do more analysis of liveness when merging heap values for such |
| // cases since stores into such references may potentially be eliminated. |
| singleton_ref = ref_info->GetReference(); |
| } |
| |
| for (HBasicBlock* predecessor : predecessors) { |
| HInstruction* pred_value = heap_values_for_[predecessor->GetBlockId()][i]; |
| if ((singleton_ref != nullptr) && |
| !singleton_ref->GetBlock()->Dominates(predecessor)) { |
| // singleton_ref is not live in this predecessor. Skip this predecessor since |
| // it does not really have the location. |
| DCHECK_EQ(pred_value, kUnknownHeapValue); |
| from_all_predecessors = false; |
| continue; |
| } |
| if (merged_value == nullptr) { |
| // First seen heap value. |
| merged_value = pred_value; |
| } else if (pred_value != merged_value) { |
| // There are conflicting values. |
| merged_value = kUnknownHeapValue; |
| break; |
| } |
| } |
| |
| if (merged_value == kUnknownHeapValue || ref_info->IsSingletonAndNonRemovable()) { |
| // There are conflicting heap values from different predecessors, |
| // or the heap value may be needed after method return or deoptimization. |
| // Keep the last store in each predecessor since future loads cannot be eliminated. |
| for (HBasicBlock* predecessor : predecessors) { |
| ScopedArenaVector<HInstruction*>& pred_values = |
| heap_values_for_[predecessor->GetBlockId()]; |
| KeepIfIsStore(pred_values[i]); |
| } |
| } |
| |
| if ((merged_value == nullptr) || !from_all_predecessors) { |
| DCHECK(singleton_ref != nullptr); |
| DCHECK((singleton_ref->GetBlock() == block) || |
| !singleton_ref->GetBlock()->Dominates(block)); |
| // singleton_ref is not defined before block or defined only in some of its |
| // predecessors, so block doesn't really have the location at its entry. |
| heap_values[i] = kUnknownHeapValue; |
| } else { |
| heap_values[i] = merged_value; |
| } |
| } |
| } |
| |
| // `instruction` is being removed. Try to see if the null check on it |
| // can be removed. This can happen if the same value is set in two branches |
| // but not in dominators. Such as: |
| // int[] a = foo(); |
| // if () { |
| // a[0] = 2; |
| // } else { |
| // a[0] = 2; |
| // } |
| // // a[0] can now be replaced with constant 2, and the null check on it can be removed. |
| void TryRemovingNullCheck(HInstruction* instruction) { |
| HInstruction* prev = instruction->GetPrevious(); |
| if ((prev != nullptr) && prev->IsNullCheck() && (prev == instruction->InputAt(0))) { |
| // Previous instruction is a null check for this instruction. Remove the null check. |
| prev->ReplaceWith(prev->InputAt(0)); |
| prev->GetBlock()->RemoveInstruction(prev); |
| } |
| } |
| |
| HInstruction* GetDefaultValue(DataType::Type type) { |
| switch (type) { |
| case DataType::Type::kReference: |
| return GetGraph()->GetNullConstant(); |
| case DataType::Type::kBool: |
| case DataType::Type::kUint8: |
| case DataType::Type::kInt8: |
| case DataType::Type::kUint16: |
| case DataType::Type::kInt16: |
| case DataType::Type::kInt32: |
| return GetGraph()->GetIntConstant(0); |
| case DataType::Type::kInt64: |
| return GetGraph()->GetLongConstant(0); |
| case DataType::Type::kFloat32: |
| return GetGraph()->GetFloatConstant(0); |
| case DataType::Type::kFloat64: |
| return GetGraph()->GetDoubleConstant(0); |
| default: |
| UNREACHABLE(); |
| } |
| } |
| |
| void VisitGetLocation(HInstruction* instruction, |
| HInstruction* ref, |
| size_t offset, |
| HInstruction* index, |
| size_t vector_length, |
| int16_t declaring_class_def_index) { |
| HInstruction* original_ref = heap_location_collector_.HuntForOriginalReference(ref); |
| ReferenceInfo* ref_info = heap_location_collector_.FindReferenceInfoOf(original_ref); |
| size_t idx = heap_location_collector_.FindHeapLocationIndex( |
| ref_info, offset, index, vector_length, declaring_class_def_index); |
| DCHECK_NE(idx, HeapLocationCollector::kHeapLocationNotFound); |
| ScopedArenaVector<HInstruction*>& heap_values = |
| heap_values_for_[instruction->GetBlock()->GetBlockId()]; |
| HInstruction* heap_value = heap_values[idx]; |
| if (heap_value == kDefaultHeapValue) { |
| HInstruction* constant = GetDefaultValue(instruction->GetType()); |
| removed_loads_.push_back(instruction); |
| substitute_instructions_for_loads_.push_back(constant); |
| heap_values[idx] = constant; |
| return; |
| } |
| if (heap_value != kUnknownHeapValue) { |
| if (heap_value->IsInstanceFieldSet() || |
| heap_value->IsArraySet() || |
| heap_value->IsVecStore()) { |
| HInstruction* store = heap_value; |
| // This load must be from a singleton since it's from the same |
| // field/element that a "removed" store puts the value. That store |
| // must be to a singleton's field/element. |
| DCHECK(ref_info->IsSingleton()); |
| // Get the real heap value of the store. |
| heap_value = heap_value->IsInstanceFieldSet() ? store->InputAt(1) : store->InputAt(2); |
| } |
| } |
| if (heap_value == kUnknownHeapValue) { |
| // Load isn't eliminated. Put the load as the value into the HeapLocation. |
| // This acts like GVN but with better aliasing analysis. |
| heap_values[idx] = instruction; |
| } else { |
| if (DataType::Kind(heap_value->GetType()) != DataType::Kind(instruction->GetType())) { |
| // The only situation where the same heap location has different type is when |
| // we do an array get on an instruction that originates from the null constant |
| // (the null could be behind a field access, an array access, a null check or |
| // a bound type). |
| // In order to stay properly typed on primitive types, we do not eliminate |
| // the array gets. |
| if (kIsDebugBuild) { |
| DCHECK(heap_value->IsArrayGet()) << heap_value->DebugName(); |
| DCHECK(instruction->IsArrayGet()) << instruction->DebugName(); |
| } |
| return; |
| } |
| removed_loads_.push_back(instruction); |
| substitute_instructions_for_loads_.push_back(heap_value); |
| TryRemovingNullCheck(instruction); |
| } |
| } |
| |
| bool Equal(HInstruction* heap_value, HInstruction* value) { |
| if (heap_value == value) { |
| return true; |
| } |
| if (heap_value == kDefaultHeapValue && GetDefaultValue(value->GetType()) == value) { |
| return true; |
| } |
| return false; |
| } |
| |
| void VisitSetLocation(HInstruction* instruction, |
| HInstruction* ref, |
| size_t offset, |
| HInstruction* index, |
| size_t vector_length, |
| int16_t declaring_class_def_index, |
| HInstruction* value) { |
| HInstruction* original_ref = heap_location_collector_.HuntForOriginalReference(ref); |
| ReferenceInfo* ref_info = heap_location_collector_.FindReferenceInfoOf(original_ref); |
| size_t idx = heap_location_collector_.FindHeapLocationIndex( |
| ref_info, offset, index, vector_length, declaring_class_def_index); |
| DCHECK_NE(idx, HeapLocationCollector::kHeapLocationNotFound); |
| ScopedArenaVector<HInstruction*>& heap_values = |
| heap_values_for_[instruction->GetBlock()->GetBlockId()]; |
| HInstruction* heap_value = heap_values[idx]; |
| bool same_value = false; |
| bool possibly_redundant = false; |
| if (Equal(heap_value, value)) { |
| // Store into the heap location with the same value. |
| same_value = true; |
| } else if (index != nullptr && ref_info->HasIndexAliasing()) { |
| // For array element, don't eliminate stores if the index can be aliased. |
| } else if (ref_info->IsSingleton()) { |
| // Store into a field/element of a singleton. The value cannot be killed due to |
| // aliasing/invocation. It can be redundant since future loads can |
| // directly get the value set by this instruction. The value can still be killed due to |
| // merging or loop side effects. Stores whose values are killed due to merging/loop side |
| // effects later will be removed from possibly_removed_stores_ when that is detected. |
| // Stores whose values may be needed after method return or deoptimization |
| // are also removed from possibly_removed_stores_ when that is detected. |
| possibly_redundant = true; |
| HLoopInformation* loop_info = instruction->GetBlock()->GetLoopInformation(); |
| if (loop_info != nullptr) { |
| // instruction is a store in the loop so the loop must does write. |
| DCHECK(side_effects_.GetLoopEffects(loop_info->GetHeader()).DoesAnyWrite()); |
| |
| if (loop_info->IsDefinedOutOfTheLoop(original_ref)) { |
| DCHECK(original_ref->GetBlock()->Dominates(loop_info->GetPreHeader())); |
| // Keep the store since its value may be needed at the loop header. |
| possibly_redundant = false; |
| } else { |
| // The singleton is created inside the loop. Value stored to it isn't needed at |
| // the loop header. This is true for outer loops also. |
| } |
| } |
| } |
| if (same_value || possibly_redundant) { |
| possibly_removed_stores_.push_back(instruction); |
| } |
| |
| if (!same_value) { |
| if (possibly_redundant) { |
| DCHECK(instruction->IsInstanceFieldSet() || |
| instruction->IsArraySet() || |
| instruction->IsVecStore()); |
| // Put the store as the heap value. If the value is loaded from heap |
| // by a load later, this store isn't really redundant. |
| heap_values[idx] = instruction; |
| } else { |
| heap_values[idx] = value; |
| } |
| } |
| // This store may kill values in other heap locations due to aliasing. |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| if (i == idx) { |
| continue; |
| } |
| if (heap_values[i] == value && !instruction->IsVecOperation()) { |
| // For field/array, same value should be kept even if aliasing happens. |
| // |
| // For vector values , this is NOT safe. For example: |
| // packed_data = [0xA, 0xB, 0xC, 0xD]; <-- Different values in each lane. |
| // VecStore array[i ,i+1,i+2,i+3] = packed_data; |
| // VecStore array[i+1,i+2,i+3,i+4] = packed_data; <-- We are here (partial overlap). |
| // VecLoad vx = array[i,i+1,i+2,i+3]; <-- Cannot be eliminated. |
| // |
| // TODO: to allow such 'same value' optimization on vector data, |
| // LSA needs to report more fine-grain MAY alias information: |
| // (1) May alias due to two vector data partial overlap. |
| // e.g. a[i..i+3] and a[i+1,..,i+4]. |
| // (2) May alias due to two vector data may complete overlap each other. |
| // e.g. a[i..i+3] and b[i..i+3]. |
| // (3) May alias but the exact relationship between two locations is unknown. |
| // e.g. a[i..i+3] and b[j..j+3], where values of a,b,i,j are all unknown. |
| // This 'same value' optimization can apply only on case (2). |
| continue; |
| } |
| if (heap_values[i] == kUnknownHeapValue) { |
| // Value is already unknown, no need for aliasing check. |
| continue; |
| } |
| if (heap_location_collector_.MayAlias(i, idx)) { |
| // Kill heap locations that may alias. |
| heap_values[i] = kUnknownHeapValue; |
| } |
| } |
| } |
| |
| void VisitInstanceFieldGet(HInstanceFieldGet* instruction) OVERRIDE { |
| HInstruction* obj = instruction->InputAt(0); |
| size_t offset = instruction->GetFieldInfo().GetFieldOffset().SizeValue(); |
| int16_t declaring_class_def_index = instruction->GetFieldInfo().GetDeclaringClassDefIndex(); |
| VisitGetLocation(instruction, |
| obj, |
| offset, |
| nullptr, |
| HeapLocation::kScalar, |
| declaring_class_def_index); |
| } |
| |
| void VisitInstanceFieldSet(HInstanceFieldSet* instruction) OVERRIDE { |
| HInstruction* obj = instruction->InputAt(0); |
| size_t offset = instruction->GetFieldInfo().GetFieldOffset().SizeValue(); |
| int16_t declaring_class_def_index = instruction->GetFieldInfo().GetDeclaringClassDefIndex(); |
| HInstruction* value = instruction->InputAt(1); |
| VisitSetLocation(instruction, |
| obj, |
| offset, |
| nullptr, |
| HeapLocation::kScalar, |
| declaring_class_def_index, |
| value); |
| } |
| |
| void VisitStaticFieldGet(HStaticFieldGet* instruction) OVERRIDE { |
| HInstruction* cls = instruction->InputAt(0); |
| size_t offset = instruction->GetFieldInfo().GetFieldOffset().SizeValue(); |
| int16_t declaring_class_def_index = instruction->GetFieldInfo().GetDeclaringClassDefIndex(); |
| VisitGetLocation(instruction, |
| cls, |
| offset, |
| nullptr, |
| HeapLocation::kScalar, |
| declaring_class_def_index); |
| } |
| |
| void VisitStaticFieldSet(HStaticFieldSet* instruction) OVERRIDE { |
| HInstruction* cls = instruction->InputAt(0); |
| size_t offset = instruction->GetFieldInfo().GetFieldOffset().SizeValue(); |
| int16_t declaring_class_def_index = instruction->GetFieldInfo().GetDeclaringClassDefIndex(); |
| HInstruction* value = instruction->InputAt(1); |
| VisitSetLocation(instruction, |
| cls, |
| offset, |
| nullptr, |
| HeapLocation::kScalar, |
| declaring_class_def_index, |
| value); |
| } |
| |
| void VisitArrayGet(HArrayGet* instruction) OVERRIDE { |
| HInstruction* array = instruction->InputAt(0); |
| HInstruction* index = instruction->InputAt(1); |
| VisitGetLocation(instruction, |
| array, |
| HeapLocation::kInvalidFieldOffset, |
| index, |
| HeapLocation::kScalar, |
| HeapLocation::kDeclaringClassDefIndexForArrays); |
| } |
| |
| void VisitArraySet(HArraySet* instruction) OVERRIDE { |
| HInstruction* array = instruction->InputAt(0); |
| HInstruction* index = instruction->InputAt(1); |
| HInstruction* value = instruction->InputAt(2); |
| VisitSetLocation(instruction, |
| array, |
| HeapLocation::kInvalidFieldOffset, |
| index, |
| HeapLocation::kScalar, |
| HeapLocation::kDeclaringClassDefIndexForArrays, |
| value); |
| } |
| |
| void VisitVecLoad(HVecLoad* instruction) OVERRIDE { |
| HInstruction* array = instruction->InputAt(0); |
| HInstruction* index = instruction->InputAt(1); |
| size_t vector_length = instruction->GetVectorLength(); |
| VisitGetLocation(instruction, |
| array, |
| HeapLocation::kInvalidFieldOffset, |
| index, |
| vector_length, |
| HeapLocation::kDeclaringClassDefIndexForArrays); |
| } |
| |
| void VisitVecStore(HVecStore* instruction) OVERRIDE { |
| HInstruction* array = instruction->InputAt(0); |
| HInstruction* index = instruction->InputAt(1); |
| HInstruction* value = instruction->InputAt(2); |
| size_t vector_length = instruction->GetVectorLength(); |
| VisitSetLocation(instruction, |
| array, |
| HeapLocation::kInvalidFieldOffset, |
| index, |
| vector_length, |
| HeapLocation::kDeclaringClassDefIndexForArrays, |
| value); |
| } |
| |
| void VisitDeoptimize(HDeoptimize* instruction) { |
| const ScopedArenaVector<HInstruction*>& heap_values = |
| heap_values_for_[instruction->GetBlock()->GetBlockId()]; |
| for (HInstruction* heap_value : heap_values) { |
| // Filter out fake instructions before checking instruction kind below. |
| if (heap_value == kUnknownHeapValue || heap_value == kDefaultHeapValue) { |
| continue; |
| } |
| // A store is kept as the heap value for possibly removed stores. |
| if (heap_value->IsInstanceFieldSet() || |
| heap_value->IsArraySet() || |
| heap_value->IsVecStore()) { |
| // Check whether the reference for a store is used by an environment local of |
| // HDeoptimize. |
| HInstruction* reference = heap_value->InputAt(0); |
| DCHECK(heap_location_collector_.FindReferenceInfoOf(reference)->IsSingleton()); |
| for (const HUseListNode<HEnvironment*>& use : reference->GetEnvUses()) { |
| HEnvironment* user = use.GetUser(); |
| if (user->GetHolder() == instruction) { |
| // The singleton for the store is visible at this deoptimization |
| // point. Need to keep the store so that the heap value is |
| // seen by the interpreter. |
| KeepIfIsStore(heap_value); |
| } |
| } |
| } |
| } |
| } |
| |
| void HandleInvoke(HInstruction* instruction) { |
| SideEffects side_effects = instruction->GetSideEffects(); |
| ScopedArenaVector<HInstruction*>& heap_values = |
| heap_values_for_[instruction->GetBlock()->GetBlockId()]; |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| ReferenceInfo* ref_info = heap_location_collector_.GetHeapLocation(i)->GetReferenceInfo(); |
| if (ref_info->IsSingleton()) { |
| // Singleton references cannot be seen by the callee. |
| } else { |
| if (side_effects.DoesAnyRead()) { |
| KeepIfIsStore(heap_values[i]); |
| } |
| if (side_effects.DoesAnyWrite()) { |
| heap_values[i] = kUnknownHeapValue; |
| } |
| } |
| } |
| } |
| |
| void VisitInvoke(HInvoke* invoke) OVERRIDE { |
| HandleInvoke(invoke); |
| } |
| |
| void VisitClinitCheck(HClinitCheck* clinit) OVERRIDE { |
| HandleInvoke(clinit); |
| } |
| |
| void VisitUnresolvedInstanceFieldGet(HUnresolvedInstanceFieldGet* instruction) OVERRIDE { |
| // Conservatively treat it as an invocation. |
| HandleInvoke(instruction); |
| } |
| |
| void VisitUnresolvedInstanceFieldSet(HUnresolvedInstanceFieldSet* instruction) OVERRIDE { |
| // Conservatively treat it as an invocation. |
| HandleInvoke(instruction); |
| } |
| |
| void VisitUnresolvedStaticFieldGet(HUnresolvedStaticFieldGet* instruction) OVERRIDE { |
| // Conservatively treat it as an invocation. |
| HandleInvoke(instruction); |
| } |
| |
| void VisitUnresolvedStaticFieldSet(HUnresolvedStaticFieldSet* instruction) OVERRIDE { |
| // Conservatively treat it as an invocation. |
| HandleInvoke(instruction); |
| } |
| |
| void VisitNewInstance(HNewInstance* new_instance) OVERRIDE { |
| ReferenceInfo* ref_info = heap_location_collector_.FindReferenceInfoOf(new_instance); |
| if (ref_info == nullptr) { |
| // new_instance isn't used for field accesses. No need to process it. |
| return; |
| } |
| if (ref_info->IsSingletonAndRemovable() && !new_instance->NeedsChecks()) { |
| DCHECK(!new_instance->IsFinalizable()); |
| singleton_new_instances_.push_back(new_instance); |
| } |
| ScopedArenaVector<HInstruction*>& heap_values = |
| heap_values_for_[new_instance->GetBlock()->GetBlockId()]; |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| HInstruction* ref = |
| heap_location_collector_.GetHeapLocation(i)->GetReferenceInfo()->GetReference(); |
| size_t offset = heap_location_collector_.GetHeapLocation(i)->GetOffset(); |
| if (ref == new_instance && offset >= mirror::kObjectHeaderSize) { |
| // Instance fields except the header fields are set to default heap values. |
| heap_values[i] = kDefaultHeapValue; |
| } |
| } |
| } |
| |
| void VisitNewArray(HNewArray* new_array) OVERRIDE { |
| ReferenceInfo* ref_info = heap_location_collector_.FindReferenceInfoOf(new_array); |
| if (ref_info == nullptr) { |
| // new_array isn't used for array accesses. No need to process it. |
| return; |
| } |
| if (ref_info->IsSingletonAndRemovable()) { |
| singleton_new_arrays_.push_back(new_array); |
| } |
| ScopedArenaVector<HInstruction*>& heap_values = |
| heap_values_for_[new_array->GetBlock()->GetBlockId()]; |
| for (size_t i = 0; i < heap_values.size(); i++) { |
| HeapLocation* location = heap_location_collector_.GetHeapLocation(i); |
| HInstruction* ref = location->GetReferenceInfo()->GetReference(); |
| if (ref == new_array && location->GetIndex() != nullptr) { |
| // Array elements are set to default heap values. |
| heap_values[i] = kDefaultHeapValue; |
| } |
| } |
| } |
| |
| // Find an instruction's substitute if it should be removed. |
| // Return the same instruction if it should not be removed. |
| HInstruction* FindSubstitute(HInstruction* instruction) { |
| size_t size = removed_loads_.size(); |
| for (size_t i = 0; i < size; i++) { |
| if (removed_loads_[i] == instruction) { |
| return substitute_instructions_for_loads_[i]; |
| } |
| } |
| return instruction; |
| } |
| |
| const HeapLocationCollector& heap_location_collector_; |
| const SideEffectsAnalysis& side_effects_; |
| |
| // Use local allocator for allocating memory. |
| ScopedArenaAllocator allocator_; |
| |
| // One array of heap values for each block. |
| ScopedArenaVector<ScopedArenaVector<HInstruction*>> heap_values_for_; |
| |
| // We record the instructions that should be eliminated but may be |
| // used by heap locations. They'll be removed in the end. |
| ScopedArenaVector<HInstruction*> removed_loads_; |
| ScopedArenaVector<HInstruction*> substitute_instructions_for_loads_; |
| |
| // Stores in this list may be removed from the list later when it's |
| // found that the store cannot be eliminated. |
| ScopedArenaVector<HInstruction*> possibly_removed_stores_; |
| |
| ScopedArenaVector<HInstruction*> singleton_new_instances_; |
| ScopedArenaVector<HInstruction*> singleton_new_arrays_; |
| |
| DISALLOW_COPY_AND_ASSIGN(LSEVisitor); |
| }; |
| |
| void LoadStoreElimination::Run() { |
| if (graph_->IsDebuggable() || graph_->HasTryCatch()) { |
| // Debugger may set heap values or trigger deoptimization of callers. |
| // Try/catch support not implemented yet. |
| // Skip this optimization. |
| return; |
| } |
| const HeapLocationCollector& heap_location_collector = lsa_.GetHeapLocationCollector(); |
| if (heap_location_collector.GetNumberOfHeapLocations() == 0) { |
| // No HeapLocation information from LSA, skip this optimization. |
| return; |
| } |
| |
| LSEVisitor lse_visitor(graph_, heap_location_collector, side_effects_, stats_); |
| for (HBasicBlock* block : graph_->GetReversePostOrder()) { |
| lse_visitor.VisitBasicBlock(block); |
| } |
| lse_visitor.RemoveInstructions(); |
| } |
| |
| } // namespace art |