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/*
* Copyright (C) 2014 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 "side_effects_analysis.h"
namespace art HIDDEN {
bool SideEffectsAnalysis::Run() {
// Inlining might have created more blocks, so we need to increase the size
// if needed.
block_effects_.resize(graph_->GetBlocks().size());
loop_effects_.resize(graph_->GetBlocks().size());
// In DEBUG mode, ensure side effects are properly initialized to empty.
if (kIsDebugBuild) {
for (HBasicBlock* block : graph_->GetReversePostOrder()) {
SideEffects effects = GetBlockEffects(block);
DCHECK(effects.DoesNothing());
if (block->IsLoopHeader()) {
effects = GetLoopEffects(block);
DCHECK(effects.DoesNothing());
}
}
}
// Do a post order visit to ensure we visit a loop header after its loop body.
for (HBasicBlock* block : graph_->GetPostOrder()) {
SideEffects effects = SideEffects::None();
// Update `effects` with the side effects of all instructions in this block.
for (HInstructionIterator inst_it(block->GetInstructions()); !inst_it.Done();
inst_it.Advance()) {
HInstruction* instruction = inst_it.Current();
effects = effects.Union(instruction->GetSideEffects());
// If all side effects are represented, scanning further will not add any
// more information to side-effects of this block.
if (effects.DoesAll()) {
break;
}
}
block_effects_[block->GetBlockId()] = effects;
if (block->IsLoopHeader()) {
// The side effects of the loop header are part of the loop.
UpdateLoopEffects(block->GetLoopInformation(), effects);
HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader();
if (pre_header->IsInLoop()) {
// Update the side effects of the outer loop with the side effects of the inner loop.
// Note that this works because we know all the blocks of the inner loop are visited
// before the loop header of the outer loop.
UpdateLoopEffects(pre_header->GetLoopInformation(), GetLoopEffects(block));
}
} else if (block->IsInLoop()) {
// Update the side effects of the loop with the side effects of this block.
UpdateLoopEffects(block->GetLoopInformation(), effects);
}
}
has_run_ = true;
return true;
}
SideEffects SideEffectsAnalysis::GetLoopEffects(HBasicBlock* block) const {
DCHECK(block->IsLoopHeader());
return loop_effects_[block->GetBlockId()];
}
SideEffects SideEffectsAnalysis::GetBlockEffects(HBasicBlock* block) const {
return block_effects_[block->GetBlockId()];
}
void SideEffectsAnalysis::UpdateLoopEffects(HLoopInformation* info, SideEffects effects) {
uint32_t id = info->GetHeader()->GetBlockId();
loop_effects_[id] = loop_effects_[id].Union(effects);
}
} // namespace art