compiler/optimizing/loop_analysis.h - platform/art - Git at Google

 /*
  * Copyright (C) 2018 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_ANALYSIS_H_
 #define ART_COMPILER_OPTIMIZING_LOOP_ANALYSIS_H_

 #include "nodes.h"

 namespace art {

 class InductionVarRange;
 class LoopAnalysis;

 // Class to hold cached information on properties of the loop.
 class LoopAnalysisInfo : public ValueObject {
  public:
   // No loop unrolling factor (just one copy of the loop-body).
   static constexpr uint32_t kNoUnrollingFactor = 1;
   // Used for unknown and non-constant trip counts (see InductionVarRange::HasKnownTripCount).
   static constexpr int64_t kUnknownTripCount = -1;

   explicit LoopAnalysisInfo(HLoopInformation* loop_info)
       : trip_count_(kUnknownTripCount),
         bb_num_(0),
         instr_num_(0),
         exits_num_(0),
         invariant_exits_num_(0),
         has_instructions_preventing_scalar_peeling_(false),
         has_instructions_preventing_scalar_unrolling_(false),
         has_long_type_instructions_(false),
         loop_info_(loop_info) {}

   int64_t GetTripCount() const { return trip_count_; }
   size_t GetNumberOfBasicBlocks() const { return bb_num_; }
   size_t GetNumberOfInstructions() const { return instr_num_; }
   size_t GetNumberOfExits() const { return exits_num_; }
   size_t GetNumberOfInvariantExits() const { return invariant_exits_num_; }

   bool HasInstructionsPreventingScalarPeeling() const {
     return has_instructions_preventing_scalar_peeling_;
   }

   bool HasInstructionsPreventingScalarUnrolling() const {
     return has_instructions_preventing_scalar_unrolling_;
   }

   bool HasInstructionsPreventingScalarOpts() const {
     return HasInstructionsPreventingScalarPeeling() || HasInstructionsPreventingScalarUnrolling();
   }

   bool HasLongTypeInstructions() const {
     return has_long_type_instructions_;
   }

   HLoopInformation* GetLoopInfo() const { return loop_info_; }

  private:
   // Trip count of the loop if known, kUnknownTripCount otherwise.
   int64_t trip_count_;
   // Number of basic blocks in the loop body.
   size_t bb_num_;
   // Number of instructions in the loop body.
   size_t instr_num_;
   // Number of loop's exits.
   size_t exits_num_;
   // Number of "if" loop exits (with HIf instruction) whose condition is loop-invariant.
   size_t invariant_exits_num_;
   // Whether the loop has instructions which make scalar loop peeling non-beneficial.
   bool has_instructions_preventing_scalar_peeling_;
   // Whether the loop has instructions which make scalar loop unrolling non-beneficial.
   bool has_instructions_preventing_scalar_unrolling_;
   // Whether the loop has instructions of primitive long type; unrolling these loop will
   // likely introduce spill/fills on 32-bit targets.
   bool has_long_type_instructions_;

   // Corresponding HLoopInformation.
   HLoopInformation* loop_info_;

   friend class LoopAnalysis;
 };

 // Placeholder class for methods and routines used to analyse loops, calculate loop properties
 // and characteristics.
 class LoopAnalysis : public ValueObject {
  public:
   // Calculates loops basic properties like body size, exits number, etc. and fills
   // 'analysis_results' with this information.
   static void CalculateLoopBasicProperties(HLoopInformation* loop_info,
                                            LoopAnalysisInfo* analysis_results,
                                            int64_t trip_count);

   // Returns the trip count of the loop if it is known and kUnknownTripCount otherwise.
   static int64_t GetLoopTripCount(HLoopInformation* loop_info,
                                   const InductionVarRange* induction_range);

  private:
   // Returns whether an instruction makes scalar loop peeling/unrolling non-beneficial.
   //
   // If in the loop body we have a dex/runtime call then its contribution to the whole
   // loop performance will probably prevail. So peeling/unrolling optimization will not bring
   // any noticeable performance improvement. It will increase the code size.
   static bool MakesScalarPeelingUnrollingNonBeneficial(HInstruction* instruction) {
     return (instruction->IsNewArray() ||
         instruction->IsNewInstance() ||
         instruction->IsUnresolvedInstanceFieldGet() ||
         instruction->IsUnresolvedInstanceFieldSet() ||
         instruction->IsUnresolvedStaticFieldGet() ||
         instruction->IsUnresolvedStaticFieldSet() ||
         // TODO: Support loops with intrinsified invokes.
         instruction->IsInvoke());
   }
 };

 //
 // Helper class which holds target-dependent methods and constants needed for loop optimizations.
 //
 // To support peeling/unrolling for a new architecture one needs to create new helper class,
 // inherit it from this and add implementation for the following methods.
 //
 class ArchNoOptsLoopHelper : public ArenaObject<kArenaAllocOptimization> {
  public:
   virtual ~ArchNoOptsLoopHelper() {}

   // Creates an instance of specialised helper for the target or default helper if the target
   // doesn't support loop peeling and unrolling.
   static ArchNoOptsLoopHelper* Create(InstructionSet isa, ArenaAllocator* allocator);

   // Returns whether the loop is not beneficial for loop peeling/unrolling.
   //
   // For example, if the loop body has too many instructions then peeling/unrolling optimization
   // will not bring any noticeable performance improvement however will increase the code size.
   //
   // Returns 'true' by default, should be overridden by particular target loop helper.
   virtual bool IsLoopNonBeneficialForScalarOpts(
       LoopAnalysisInfo* loop_analysis_info ATTRIBUTE_UNUSED) const { return true; }

   // Returns optimal scalar unrolling factor for the loop.
   //
   // Returns kNoUnrollingFactor by default, should be overridden by particular target loop helper.
   virtual uint32_t GetScalarUnrollingFactor(
       const LoopAnalysisInfo* analysis_info ATTRIBUTE_UNUSED) const {
     return LoopAnalysisInfo::kNoUnrollingFactor;
   }

   // Returns whether scalar loop peeling is enabled,
   //
   // Returns 'false' by default, should be overridden by particular target loop helper.
   virtual bool IsLoopPeelingEnabled() const { return false; }

   // Returns whether it is beneficial to fully unroll the loop.
   //
   // Returns 'false' by default, should be overridden by particular target loop helper.
   virtual bool IsFullUnrollingBeneficial(LoopAnalysisInfo* analysis_info ATTRIBUTE_UNUSED) const {
     return false;
   }

   // Returns optimal SIMD unrolling factor for the loop.
   //
   // Returns kNoUnrollingFactor by default, should be overridden by particular target loop helper.
   virtual uint32_t GetSIMDUnrollingFactor(HBasicBlock* block ATTRIBUTE_UNUSED,
                                           int64_t trip_count ATTRIBUTE_UNUSED,
                                           uint32_t max_peel ATTRIBUTE_UNUSED,
                                           uint32_t vector_length ATTRIBUTE_UNUSED) const {
     return LoopAnalysisInfo::kNoUnrollingFactor;
   }
 };

 }  // namespace art

 #endif  // ART_COMPILER_OPTIMIZING_LOOP_ANALYSIS_H_
	/*
	* Copyright (C) 2018 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_ANALYSIS_H_
	#define ART_COMPILER_OPTIMIZING_LOOP_ANALYSIS_H_

	#include "nodes.h"

	namespace art {

	class InductionVarRange;
	class LoopAnalysis;

	// Class to hold cached information on properties of the loop.
	class LoopAnalysisInfo : public ValueObject {
	public:
	// No loop unrolling factor (just one copy of the loop-body).
	static constexpr uint32_t kNoUnrollingFactor = 1;
	// Used for unknown and non-constant trip counts (see InductionVarRange::HasKnownTripCount).
	static constexpr int64_t kUnknownTripCount = -1;

	explicit LoopAnalysisInfo(HLoopInformation* loop_info)
	: trip_count_(kUnknownTripCount),
	bb_num_(0),
	instr_num_(0),
	exits_num_(0),
	invariant_exits_num_(0),
	has_instructions_preventing_scalar_peeling_(false),
	has_instructions_preventing_scalar_unrolling_(false),
	has_long_type_instructions_(false),
	loop_info_(loop_info) {}

	int64_t GetTripCount() const { return trip_count_; }
	size_t GetNumberOfBasicBlocks() const { return bb_num_; }
	size_t GetNumberOfInstructions() const { return instr_num_; }
	size_t GetNumberOfExits() const { return exits_num_; }
	size_t GetNumberOfInvariantExits() const { return invariant_exits_num_; }

	bool HasInstructionsPreventingScalarPeeling() const {
	return has_instructions_preventing_scalar_peeling_;
	}

	bool HasInstructionsPreventingScalarUnrolling() const {
	return has_instructions_preventing_scalar_unrolling_;
	}

	bool HasInstructionsPreventingScalarOpts() const {
	return HasInstructionsPreventingScalarPeeling() \|\| HasInstructionsPreventingScalarUnrolling();
	}

	bool HasLongTypeInstructions() const {
	return has_long_type_instructions_;
	}

	HLoopInformation* GetLoopInfo() const { return loop_info_; }

	private:
	// Trip count of the loop if known, kUnknownTripCount otherwise.
	int64_t trip_count_;
	// Number of basic blocks in the loop body.
	size_t bb_num_;
	// Number of instructions in the loop body.
	size_t instr_num_;
	// Number of loop's exits.
	size_t exits_num_;
	// Number of "if" loop exits (with HIf instruction) whose condition is loop-invariant.
	size_t invariant_exits_num_;
	// Whether the loop has instructions which make scalar loop peeling non-beneficial.
	bool has_instructions_preventing_scalar_peeling_;
	// Whether the loop has instructions which make scalar loop unrolling non-beneficial.
	bool has_instructions_preventing_scalar_unrolling_;
	// Whether the loop has instructions of primitive long type; unrolling these loop will
	// likely introduce spill/fills on 32-bit targets.
	bool has_long_type_instructions_;

	// Corresponding HLoopInformation.
	HLoopInformation* loop_info_;

	friend class LoopAnalysis;
	};

	// Placeholder class for methods and routines used to analyse loops, calculate loop properties
	// and characteristics.
	class LoopAnalysis : public ValueObject {
	public:
	// Calculates loops basic properties like body size, exits number, etc. and fills
	// 'analysis_results' with this information.
	static void CalculateLoopBasicProperties(HLoopInformation* loop_info,
	LoopAnalysisInfo* analysis_results,
	int64_t trip_count);

	// Returns the trip count of the loop if it is known and kUnknownTripCount otherwise.
	static int64_t GetLoopTripCount(HLoopInformation* loop_info,
	const InductionVarRange* induction_range);

	private:
	// Returns whether an instruction makes scalar loop peeling/unrolling non-beneficial.
	//
	// If in the loop body we have a dex/runtime call then its contribution to the whole
	// loop performance will probably prevail. So peeling/unrolling optimization will not bring
	// any noticeable performance improvement. It will increase the code size.
	static bool MakesScalarPeelingUnrollingNonBeneficial(HInstruction* instruction) {
	return (instruction->IsNewArray() \|\|
	instruction->IsNewInstance() \|\|
	instruction->IsUnresolvedInstanceFieldGet() \|\|
	instruction->IsUnresolvedInstanceFieldSet() \|\|
	instruction->IsUnresolvedStaticFieldGet() \|\|
	instruction->IsUnresolvedStaticFieldSet() \|\|
	// TODO: Support loops with intrinsified invokes.
	instruction->IsInvoke());
	}
	};

	//
	// Helper class which holds target-dependent methods and constants needed for loop optimizations.
	//
	// To support peeling/unrolling for a new architecture one needs to create new helper class,
	// inherit it from this and add implementation for the following methods.
	//
	class ArchNoOptsLoopHelper : public ArenaObject<kArenaAllocOptimization> {
	public:
	virtual ~ArchNoOptsLoopHelper() {}

	// Creates an instance of specialised helper for the target or default helper if the target
	// doesn't support loop peeling and unrolling.
	static ArchNoOptsLoopHelper* Create(InstructionSet isa, ArenaAllocator* allocator);

	// Returns whether the loop is not beneficial for loop peeling/unrolling.
	//
	// For example, if the loop body has too many instructions then peeling/unrolling optimization
	// will not bring any noticeable performance improvement however will increase the code size.
	//
	// Returns 'true' by default, should be overridden by particular target loop helper.
	virtual bool IsLoopNonBeneficialForScalarOpts(
	LoopAnalysisInfo* loop_analysis_info ATTRIBUTE_UNUSED) const { return true; }

	// Returns optimal scalar unrolling factor for the loop.
	//
	// Returns kNoUnrollingFactor by default, should be overridden by particular target loop helper.
	virtual uint32_t GetScalarUnrollingFactor(
	const LoopAnalysisInfo* analysis_info ATTRIBUTE_UNUSED) const {
	return LoopAnalysisInfo::kNoUnrollingFactor;
	}

	// Returns whether scalar loop peeling is enabled,
	//
	// Returns 'false' by default, should be overridden by particular target loop helper.
	virtual bool IsLoopPeelingEnabled() const { return false; }

	// Returns whether it is beneficial to fully unroll the loop.
	//
	// Returns 'false' by default, should be overridden by particular target loop helper.
	virtual bool IsFullUnrollingBeneficial(LoopAnalysisInfo* analysis_info ATTRIBUTE_UNUSED) const {
	return false;
	}

	// Returns optimal SIMD unrolling factor for the loop.
	//
	// Returns kNoUnrollingFactor by default, should be overridden by particular target loop helper.
	virtual uint32_t GetSIMDUnrollingFactor(HBasicBlock* block ATTRIBUTE_UNUSED,
	int64_t trip_count ATTRIBUTE_UNUSED,
	uint32_t max_peel ATTRIBUTE_UNUSED,
	uint32_t vector_length ATTRIBUTE_UNUSED) const {
	return LoopAnalysisInfo::kNoUnrollingFactor;
	}
	};

	} // namespace art

	#endif // ART_COMPILER_OPTIMIZING_LOOP_ANALYSIS_H_