673 lines
27 KiB
C++
673 lines
27 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "load_store_analysis.h"
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#include "load_store_elimination.h"
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#include "escape.h"
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#include "side_effects_analysis.h"
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#include <iostream>
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namespace art {
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// An unknown heap value. Loads with such a value in the heap location cannot be eliminated.
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// A heap location can be set to kUnknownHeapValue when:
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// - initially set a value.
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// - killed due to aliasing, merging, invocation, or loop side effects.
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static HInstruction* const kUnknownHeapValue =
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reinterpret_cast<HInstruction*>(static_cast<uintptr_t>(-1));
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// Default heap value after an allocation.
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// A heap location can be set to that value right after an allocation.
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static HInstruction* const kDefaultHeapValue =
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reinterpret_cast<HInstruction*>(static_cast<uintptr_t>(-2));
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class LSEVisitor : public HGraphVisitor {
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public:
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LSEVisitor(HGraph* graph,
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const HeapLocationCollector& heap_locations_collector,
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const SideEffectsAnalysis& side_effects)
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: HGraphVisitor(graph),
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heap_location_collector_(heap_locations_collector),
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side_effects_(side_effects),
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heap_values_for_(graph->GetBlocks().size(),
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ArenaVector<HInstruction*>(heap_locations_collector.
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GetNumberOfHeapLocations(),
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kUnknownHeapValue,
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graph->GetArena()->Adapter(kArenaAllocLSE)),
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graph->GetArena()->Adapter(kArenaAllocLSE)),
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removed_loads_(graph->GetArena()->Adapter(kArenaAllocLSE)),
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substitute_instructions_for_loads_(graph->GetArena()->Adapter(kArenaAllocLSE)),
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possibly_removed_stores_(graph->GetArena()->Adapter(kArenaAllocLSE)),
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singleton_new_instances_(graph->GetArena()->Adapter(kArenaAllocLSE)),
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singleton_new_arrays_(graph->GetArena()->Adapter(kArenaAllocLSE)) {
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}
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void VisitBasicBlock(HBasicBlock* block) OVERRIDE {
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// Populate the heap_values array for this block.
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// TODO: try to reuse the heap_values array from one predecessor if possible.
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if (block->IsLoopHeader()) {
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HandleLoopSideEffects(block);
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} else {
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MergePredecessorValues(block);
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}
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HGraphVisitor::VisitBasicBlock(block);
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}
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// Remove recorded instructions that should be eliminated.
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void RemoveInstructions() {
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size_t size = removed_loads_.size();
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DCHECK_EQ(size, substitute_instructions_for_loads_.size());
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for (size_t i = 0; i < size; i++) {
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HInstruction* load = removed_loads_[i];
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DCHECK(load != nullptr);
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DCHECK(load->IsInstanceFieldGet() ||
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load->IsStaticFieldGet() ||
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load->IsArrayGet());
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HInstruction* substitute = substitute_instructions_for_loads_[i];
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DCHECK(substitute != nullptr);
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// Keep tracing substitute till one that's not removed.
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HInstruction* sub_sub = FindSubstitute(substitute);
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while (sub_sub != substitute) {
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substitute = sub_sub;
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sub_sub = FindSubstitute(substitute);
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}
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load->ReplaceWith(substitute);
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load->GetBlock()->RemoveInstruction(load);
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}
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// At this point, stores in possibly_removed_stores_ can be safely removed.
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for (HInstruction* store : possibly_removed_stores_) {
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DCHECK(store->IsInstanceFieldSet() || store->IsStaticFieldSet() || store->IsArraySet());
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store->GetBlock()->RemoveInstruction(store);
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}
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// Eliminate singleton-classified instructions:
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// * - Constructor fences (they never escape this thread).
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// * - Allocations (if they are unused).
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for (HInstruction* new_instance : singleton_new_instances_) {
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HConstructorFence::RemoveConstructorFences(new_instance);
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if (!new_instance->HasNonEnvironmentUses()) {
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new_instance->RemoveEnvironmentUsers();
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new_instance->GetBlock()->RemoveInstruction(new_instance);
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}
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}
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for (HInstruction* new_array : singleton_new_arrays_) {
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HConstructorFence::RemoveConstructorFences(new_array);
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if (!new_array->HasNonEnvironmentUses()) {
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new_array->RemoveEnvironmentUsers();
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new_array->GetBlock()->RemoveInstruction(new_array);
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}
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}
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}
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private:
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// If heap_values[index] is an instance field store, need to keep the store.
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// This is necessary if a heap value is killed due to merging, or loop side
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// effects (which is essentially merging also), since a load later from the
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// location won't be eliminated.
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void KeepIfIsStore(HInstruction* heap_value) {
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if (heap_value == kDefaultHeapValue ||
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heap_value == kUnknownHeapValue ||
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!(heap_value->IsInstanceFieldSet() || heap_value->IsArraySet())) {
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return;
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}
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auto idx = std::find(possibly_removed_stores_.begin(),
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possibly_removed_stores_.end(), heap_value);
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if (idx != possibly_removed_stores_.end()) {
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// Make sure the store is kept.
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possibly_removed_stores_.erase(idx);
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}
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}
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void HandleLoopSideEffects(HBasicBlock* block) {
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DCHECK(block->IsLoopHeader());
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int block_id = block->GetBlockId();
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ArenaVector<HInstruction*>& heap_values = heap_values_for_[block_id];
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// Don't eliminate loads in irreducible loops. This is safe for singletons, because
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// they are always used by the non-eliminated loop-phi.
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if (block->GetLoopInformation()->IsIrreducible()) {
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if (kIsDebugBuild) {
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for (size_t i = 0; i < heap_values.size(); i++) {
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DCHECK_EQ(heap_values[i], kUnknownHeapValue);
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}
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}
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return;
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}
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HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader();
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ArenaVector<HInstruction*>& pre_header_heap_values =
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heap_values_for_[pre_header->GetBlockId()];
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// Inherit the values from pre-header.
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for (size_t i = 0; i < heap_values.size(); i++) {
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heap_values[i] = pre_header_heap_values[i];
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}
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// We do a single pass in reverse post order. For loops, use the side effects as a hint
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// to see if the heap values should be killed.
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if (side_effects_.GetLoopEffects(block).DoesAnyWrite()) {
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for (size_t i = 0; i < heap_values.size(); i++) {
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HeapLocation* location = heap_location_collector_.GetHeapLocation(i);
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ReferenceInfo* ref_info = location->GetReferenceInfo();
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if (ref_info->IsSingletonAndRemovable() &&
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!location->IsValueKilledByLoopSideEffects()) {
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// A removable singleton's field that's not stored into inside a loop is
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// invariant throughout the loop. Nothing to do.
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DCHECK(ref_info->IsSingletonAndRemovable());
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} else {
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// heap value is killed by loop side effects (stored into directly, or
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// due to aliasing). Or the heap value may be needed after method return
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// or deoptimization.
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KeepIfIsStore(pre_header_heap_values[i]);
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heap_values[i] = kUnknownHeapValue;
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}
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}
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}
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}
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void MergePredecessorValues(HBasicBlock* block) {
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const ArenaVector<HBasicBlock*>& predecessors = block->GetPredecessors();
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if (predecessors.size() == 0) {
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return;
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}
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ArenaVector<HInstruction*>& heap_values = heap_values_for_[block->GetBlockId()];
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for (size_t i = 0; i < heap_values.size(); i++) {
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HInstruction* merged_value = nullptr;
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// Whether merged_value is a result that's merged from all predecessors.
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bool from_all_predecessors = true;
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ReferenceInfo* ref_info = heap_location_collector_.GetHeapLocation(i)->GetReferenceInfo();
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HInstruction* singleton_ref = nullptr;
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if (ref_info->IsSingleton()) {
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// We do more analysis of liveness when merging heap values for such
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// cases since stores into such references may potentially be eliminated.
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singleton_ref = ref_info->GetReference();
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}
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for (HBasicBlock* predecessor : predecessors) {
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HInstruction* pred_value = heap_values_for_[predecessor->GetBlockId()][i];
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if ((singleton_ref != nullptr) &&
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!singleton_ref->GetBlock()->Dominates(predecessor)) {
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// singleton_ref is not live in this predecessor. Skip this predecessor since
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// it does not really have the location.
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DCHECK_EQ(pred_value, kUnknownHeapValue);
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from_all_predecessors = false;
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continue;
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}
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if (merged_value == nullptr) {
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// First seen heap value.
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merged_value = pred_value;
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} else if (pred_value != merged_value) {
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// There are conflicting values.
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merged_value = kUnknownHeapValue;
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break;
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}
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}
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if (merged_value == kUnknownHeapValue || ref_info->IsSingletonAndNonRemovable()) {
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// There are conflicting heap values from different predecessors,
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// or the heap value may be needed after method return or deoptimization.
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// Keep the last store in each predecessor since future loads cannot be eliminated.
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for (HBasicBlock* predecessor : predecessors) {
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ArenaVector<HInstruction*>& pred_values = heap_values_for_[predecessor->GetBlockId()];
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KeepIfIsStore(pred_values[i]);
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}
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}
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if ((merged_value == nullptr) || !from_all_predecessors) {
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DCHECK(singleton_ref != nullptr);
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DCHECK((singleton_ref->GetBlock() == block) ||
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!singleton_ref->GetBlock()->Dominates(block));
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// singleton_ref is not defined before block or defined only in some of its
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// predecessors, so block doesn't really have the location at its entry.
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heap_values[i] = kUnknownHeapValue;
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} else {
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heap_values[i] = merged_value;
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}
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}
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}
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// `instruction` is being removed. Try to see if the null check on it
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// can be removed. This can happen if the same value is set in two branches
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// but not in dominators. Such as:
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// int[] a = foo();
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// if () {
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// a[0] = 2;
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// } else {
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// a[0] = 2;
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// }
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// // a[0] can now be replaced with constant 2, and the null check on it can be removed.
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void TryRemovingNullCheck(HInstruction* instruction) {
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HInstruction* prev = instruction->GetPrevious();
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if ((prev != nullptr) && prev->IsNullCheck() && (prev == instruction->InputAt(0))) {
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// Previous instruction is a null check for this instruction. Remove the null check.
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prev->ReplaceWith(prev->InputAt(0));
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prev->GetBlock()->RemoveInstruction(prev);
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}
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}
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HInstruction* GetDefaultValue(Primitive::Type type) {
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switch (type) {
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case Primitive::kPrimNot:
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return GetGraph()->GetNullConstant();
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case Primitive::kPrimBoolean:
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case Primitive::kPrimByte:
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case Primitive::kPrimChar:
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case Primitive::kPrimShort:
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case Primitive::kPrimInt:
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return GetGraph()->GetIntConstant(0);
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case Primitive::kPrimLong:
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return GetGraph()->GetLongConstant(0);
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case Primitive::kPrimFloat:
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return GetGraph()->GetFloatConstant(0);
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case Primitive::kPrimDouble:
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return GetGraph()->GetDoubleConstant(0);
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default:
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UNREACHABLE();
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}
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}
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void VisitGetLocation(HInstruction* instruction,
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HInstruction* ref,
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size_t offset,
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HInstruction* index,
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int16_t declaring_class_def_index) {
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HInstruction* original_ref = heap_location_collector_.HuntForOriginalReference(ref);
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ReferenceInfo* ref_info = heap_location_collector_.FindReferenceInfoOf(original_ref);
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size_t idx = heap_location_collector_.FindHeapLocationIndex(
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ref_info, offset, index, declaring_class_def_index);
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DCHECK_NE(idx, HeapLocationCollector::kHeapLocationNotFound);
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ArenaVector<HInstruction*>& heap_values =
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heap_values_for_[instruction->GetBlock()->GetBlockId()];
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HInstruction* heap_value = heap_values[idx];
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if (heap_value == kDefaultHeapValue) {
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HInstruction* constant = GetDefaultValue(instruction->GetType());
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removed_loads_.push_back(instruction);
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substitute_instructions_for_loads_.push_back(constant);
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heap_values[idx] = constant;
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return;
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}
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if (heap_value != kUnknownHeapValue) {
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if (heap_value->IsInstanceFieldSet() || heap_value->IsArraySet()) {
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HInstruction* store = heap_value;
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// This load must be from a singleton since it's from the same
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// field/element that a "removed" store puts the value. That store
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// must be to a singleton's field/element.
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DCHECK(ref_info->IsSingleton());
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// Get the real heap value of the store.
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heap_value = heap_value->IsInstanceFieldSet() ? store->InputAt(1) : store->InputAt(2);
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}
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}
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if (heap_value == kUnknownHeapValue) {
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// Load isn't eliminated. Put the load as the value into the HeapLocation.
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// This acts like GVN but with better aliasing analysis.
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heap_values[idx] = instruction;
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} else {
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if (Primitive::PrimitiveKind(heap_value->GetType())
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!= Primitive::PrimitiveKind(instruction->GetType())) {
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// The only situation where the same heap location has different type is when
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// we do an array get on an instruction that originates from the null constant
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// (the null could be behind a field access, an array access, a null check or
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// a bound type).
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// In order to stay properly typed on primitive types, we do not eliminate
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// the array gets.
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if (kIsDebugBuild) {
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DCHECK(heap_value->IsArrayGet()) << heap_value->DebugName();
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DCHECK(instruction->IsArrayGet()) << instruction->DebugName();
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}
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return;
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}
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removed_loads_.push_back(instruction);
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substitute_instructions_for_loads_.push_back(heap_value);
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TryRemovingNullCheck(instruction);
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}
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}
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bool Equal(HInstruction* heap_value, HInstruction* value) {
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if (heap_value == value) {
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return true;
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}
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if (heap_value == kDefaultHeapValue && GetDefaultValue(value->GetType()) == value) {
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return true;
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}
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return false;
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}
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void VisitSetLocation(HInstruction* instruction,
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HInstruction* ref,
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size_t offset,
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HInstruction* index,
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int16_t declaring_class_def_index,
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HInstruction* value) {
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HInstruction* original_ref = heap_location_collector_.HuntForOriginalReference(ref);
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ReferenceInfo* ref_info = heap_location_collector_.FindReferenceInfoOf(original_ref);
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size_t idx = heap_location_collector_.FindHeapLocationIndex(
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ref_info, offset, index, declaring_class_def_index);
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DCHECK_NE(idx, HeapLocationCollector::kHeapLocationNotFound);
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ArenaVector<HInstruction*>& heap_values =
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heap_values_for_[instruction->GetBlock()->GetBlockId()];
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HInstruction* heap_value = heap_values[idx];
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bool same_value = false;
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bool possibly_redundant = false;
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if (Equal(heap_value, value)) {
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// Store into the heap location with the same value.
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same_value = true;
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} else if (index != nullptr && ref_info->HasIndexAliasing()) {
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// For array element, don't eliminate stores if the index can be aliased.
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} else if (ref_info->IsSingleton()) {
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// Store into a field of a singleton. The value cannot be killed due to
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// aliasing/invocation. It can be redundant since future loads can
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// directly get the value set by this instruction. The value can still be killed due to
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// merging or loop side effects. Stores whose values are killed due to merging/loop side
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// effects later will be removed from possibly_removed_stores_ when that is detected.
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// Stores whose values may be needed after method return or deoptimization
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// are also removed from possibly_removed_stores_ when that is detected.
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possibly_redundant = true;
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HNewInstance* new_instance = ref_info->GetReference()->AsNewInstance();
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if (new_instance != nullptr && new_instance->IsFinalizable()) {
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// Finalizable objects escape globally. Need to keep the store.
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possibly_redundant = false;
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} else {
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HLoopInformation* loop_info = instruction->GetBlock()->GetLoopInformation();
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if (loop_info != nullptr) {
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// instruction is a store in the loop so the loop must does write.
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DCHECK(side_effects_.GetLoopEffects(loop_info->GetHeader()).DoesAnyWrite());
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if (loop_info->IsDefinedOutOfTheLoop(original_ref)) {
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DCHECK(original_ref->GetBlock()->Dominates(loop_info->GetPreHeader()));
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// Keep the store since its value may be needed at the loop header.
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possibly_redundant = false;
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} else {
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// The singleton is created inside the loop. Value stored to it isn't needed at
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// the loop header. This is true for outer loops also.
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}
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}
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}
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}
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if (same_value || possibly_redundant) {
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possibly_removed_stores_.push_back(instruction);
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}
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if (!same_value) {
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if (possibly_redundant) {
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DCHECK(instruction->IsInstanceFieldSet() || instruction->IsArraySet());
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// Put the store as the heap value. If the value is loaded from heap
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// by a load later, this store isn't really redundant.
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heap_values[idx] = instruction;
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} else {
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heap_values[idx] = value;
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}
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}
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// This store may kill values in other heap locations due to aliasing.
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for (size_t i = 0; i < heap_values.size(); i++) {
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if (i == idx) {
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continue;
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}
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if (heap_values[i] == value) {
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// Same value should be kept even if aliasing happens.
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continue;
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}
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if (heap_values[i] == kUnknownHeapValue) {
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// Value is already unknown, no need for aliasing check.
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continue;
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}
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if (heap_location_collector_.MayAlias(i, idx)) {
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// Kill heap locations that may alias.
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heap_values[i] = kUnknownHeapValue;
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}
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}
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}
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void VisitInstanceFieldGet(HInstanceFieldGet* instruction) OVERRIDE {
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HInstruction* obj = instruction->InputAt(0);
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size_t offset = instruction->GetFieldInfo().GetFieldOffset().SizeValue();
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int16_t declaring_class_def_index = instruction->GetFieldInfo().GetDeclaringClassDefIndex();
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VisitGetLocation(instruction, obj, offset, nullptr, declaring_class_def_index);
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}
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void VisitInstanceFieldSet(HInstanceFieldSet* instruction) OVERRIDE {
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HInstruction* obj = instruction->InputAt(0);
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size_t offset = instruction->GetFieldInfo().GetFieldOffset().SizeValue();
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int16_t declaring_class_def_index = instruction->GetFieldInfo().GetDeclaringClassDefIndex();
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HInstruction* value = instruction->InputAt(1);
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VisitSetLocation(instruction, obj, offset, nullptr, declaring_class_def_index, value);
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}
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void VisitStaticFieldGet(HStaticFieldGet* instruction) OVERRIDE {
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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, 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, 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::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::kDeclaringClassDefIndexForArrays,
|
|
value);
|
|
}
|
|
|
|
void VisitDeoptimize(HDeoptimize* instruction) {
|
|
const ArenaVector<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()) {
|
|
// 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* invoke) {
|
|
ArenaVector<HInstruction*>& heap_values =
|
|
heap_values_for_[invoke->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 {
|
|
heap_values[i] = kUnknownHeapValue;
|
|
}
|
|
}
|
|
}
|
|
|
|
void VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) OVERRIDE {
|
|
HandleInvoke(invoke);
|
|
}
|
|
|
|
void VisitInvokeVirtual(HInvokeVirtual* invoke) OVERRIDE {
|
|
HandleInvoke(invoke);
|
|
}
|
|
|
|
void VisitInvokeInterface(HInvokeInterface* invoke) OVERRIDE {
|
|
HandleInvoke(invoke);
|
|
}
|
|
|
|
void VisitInvokeUnresolved(HInvokeUnresolved* invoke) OVERRIDE {
|
|
HandleInvoke(invoke);
|
|
}
|
|
|
|
void VisitInvokePolymorphic(HInvokePolymorphic* 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->IsFinalizable() &&
|
|
!new_instance->NeedsChecks()) {
|
|
singleton_new_instances_.push_back(new_instance);
|
|
}
|
|
ArenaVector<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);
|
|
}
|
|
ArenaVector<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_;
|
|
|
|
// One array of heap values for each block.
|
|
ArenaVector<ArenaVector<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.
|
|
ArenaVector<HInstruction*> removed_loads_;
|
|
ArenaVector<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.
|
|
ArenaVector<HInstruction*> possibly_removed_stores_;
|
|
|
|
ArenaVector<HInstruction*> singleton_new_instances_;
|
|
ArenaVector<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_);
|
|
for (HBasicBlock* block : graph_->GetReversePostOrder()) {
|
|
lse_visitor.VisitBasicBlock(block);
|
|
}
|
|
lse_visitor.RemoveInstructions();
|
|
}
|
|
|
|
} // namespace art
|