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/*
* Copyright (C) 2017 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.
*/
#ifndef ART_COMPILER_OPTIMIZING_CONSTRUCTOR_FENCE_REDUNDANCY_ELIMINATION_H_
#define ART_COMPILER_OPTIMIZING_CONSTRUCTOR_FENCE_REDUNDANCY_ELIMINATION_H_
#include "base/macros.h"
#include "optimization.h"
namespace art HIDDEN {
/*
* Constructor Fence Redundancy Elimination (CFRE).
*
* A local optimization pass that merges redundant constructor fences
* together within the same basic block.
*
* Abbreviations:
* - CF: Constructor Fence
* - CFS: Constructor Fence Set
* - CFTargets: The unique set of the inputs of all the instructions in CFS.
*
* Given any CFS = { CF(x), CF(y), CF(z), ... }, define CFTargets = { x, y, z, ... }.
* - Publish(R) must not exist for any R in CFTargets if this Publish(R) is between any CF in CFS.
* - This type of Publish(R) is called an "interesting publish".
*
* A Publish(R) is considered any instruction at which the reference to "R"
* may escape (e.g. invoke, store, return, etc) to another thread.
*
* Starting at the beginning of the block:
* - Find the largest contiguous CFS.
* - If we see an interesting publish, merge all instructions in CFS into a single CF(CFTargets).
* - Repeat until the block is fully visited.
* - At the end of the block, merge all instructions in CFS into a single CF(CFTargets).
*/
class ConstructorFenceRedundancyElimination : public HOptimization {
public:
ConstructorFenceRedundancyElimination(HGraph* graph,
OptimizingCompilerStats* stats,
const char* name = kCFREPassName)
: HOptimization(graph, name, stats) {}
bool Run() override;
static constexpr const char* kCFREPassName = "constructor_fence_redundancy_elimination";
private:
DISALLOW_COPY_AND_ASSIGN(ConstructorFenceRedundancyElimination);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_CONSTRUCTOR_FENCE_REDUNDANCY_ELIMINATION_H_
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