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/*
* Copyright (C) 2016 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_LOOP_OPTIMIZATION_H_
#define ART_COMPILER_OPTIMIZING_LOOP_OPTIMIZATION_H_
#include "induction_var_range.h"
#include "nodes.h"
#include "optimization.h"
namespace art {
/**
* Loop optimizations. Builds a loop hierarchy and applies optimizations to
* the detected nested loops, such as removal of dead induction and empty loops.
*/
class HLoopOptimization : public HOptimization {
public:
HLoopOptimization(HGraph* graph, HInductionVarAnalysis* induction_analysis);
void Run() OVERRIDE;
static constexpr const char* kLoopOptimizationPassName = "loop_optimization";
private:
/**
* A single loop inside the loop hierarchy representation.
*/
struct LoopNode : public ArenaObject<kArenaAllocLoopOptimization> {
explicit LoopNode(HLoopInformation* lp_info)
: loop_info(lp_info),
outer(nullptr),
inner(nullptr),
previous(nullptr),
next(nullptr) {}
HLoopInformation* const loop_info;
LoopNode* outer;
LoopNode* inner;
LoopNode* previous;
LoopNode* next;
};
void LocalRun();
void AddLoop(HLoopInformation* loop_info);
void RemoveLoop(LoopNode* node);
void TraverseLoopsInnerToOuter(LoopNode* node);
void SimplifyInduction(LoopNode* node);
void SimplifyBlocks(LoopNode* node);
void RemoveIfEmptyInnerLoop(LoopNode* node);
bool IsPhiInduction(HPhi* phi);
bool IsEmptyHeader(HBasicBlock* block);
bool IsEmptyBody(HBasicBlock* block);
bool IsOnlyUsedAfterLoop(HLoopInformation* loop_info,
HInstruction* instruction,
/*out*/ int32_t* use_count);
void ReplaceAllUses(HInstruction* instruction, HInstruction* replacement);
bool TryReplaceWithLastValue(HInstruction* instruction, HBasicBlock* block);
// Range information based on prior induction variable analysis.
InductionVarRange induction_range_;
// Phase-local heap memory allocator for the loop optimizer. Storage obtained
// through this allocator is immediately released when the loop optimizer is done.
ArenaAllocator* loop_allocator_;
// Entries into the loop hierarchy representation. The hierarchy resides
// in phase-local heap memory.
LoopNode* top_loop_;
LoopNode* last_loop_;
// Temporary bookkeeping of a set of instructions.
// Contents reside in phase-local heap memory.
ArenaSet<HInstruction*>* iset_;
// Counter that tracks how many induction cycles have been simplified. Useful
// to trigger incremental updates of induction variable analysis of outer loops
// when the induction of inner loops has changed.
int32_t induction_simplication_count_;
// Flag that tracks if any simplifications have occurred.
bool simplified_;
friend class LoopOptimizationTest;
DISALLOW_COPY_AND_ASSIGN(HLoopOptimization);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_LOOP_OPTIMIZATION_H_
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