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

 /*
  * Copyright (C) 2015 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_INDUCTION_VAR_ANALYSIS_H_
 #define ART_COMPILER_OPTIMIZING_INDUCTION_VAR_ANALYSIS_H_

 #include <string>

 #include "nodes.h"
 #include "optimization.h"

 namespace art {

 /**
  * Induction variable analysis. This class does not have a direct public API.
  * Instead, the results of induction variable analysis can be queried through
  * friend classes, such as InductionVarRange.
  *
  * The analysis implementation is based on the paper by M. Gerlek et al.
  * "Beyond Induction Variables: Detecting and Classifying Sequences Using a Demand-Driven SSA Form"
  * (ACM Transactions on Programming Languages and Systems, Volume 17 Issue 1, Jan. 1995).
  */
 class HInductionVarAnalysis : public HOptimization {
  public:
   explicit HInductionVarAnalysis(HGraph* graph, const char* name = kInductionPassName);

   bool Run() override;

   static constexpr const char* kInductionPassName = "induction_var_analysis";

  private:
   struct NodeInfo {
     explicit NodeInfo(uint32_t d) : depth(d), done(false) {}
     uint32_t depth;
     bool done;
   };

   enum InductionClass {
     kInvariant,
     kLinear,
     kPolynomial,
     kGeometric,
     kWrapAround,
     kPeriodic
   };

   enum InductionOp {
     // Operations.
     kNop,
     kAdd,
     kSub,
     kNeg,
     kMul,
     kDiv,
     kRem,
     kXor,
     kFetch,
     // Trip-counts.
     kTripCountInLoop,        // valid in full loop; loop is finite
     kTripCountInBody,        // valid in body only; loop is finite
     kTripCountInLoopUnsafe,  // valid in full loop; loop may be infinite
     kTripCountInBodyUnsafe,  // valid in body only; loop may be infinite
     // Comparisons for trip-count tests.
     kLT,
     kLE,
     kGT,
     kGE
   };

   /**
    * Defines a detected induction as:
    *   (1) invariant:
    *         op: a + b, a - b, -b, a * b, a / b, a % b, a ^ b, fetch
    *   (2) linear:
    *         nop: a * i + b
    *   (3) polynomial:
    *         nop: sum_lt(a) + b, for linear a
    *   (4) geometric:
    *         op: a * fetch^i + b, a * fetch^-i + b
    *   (5) wrap-around
    *         nop: a, then defined by b
    *   (6) periodic
    *         nop: a, then defined by b (repeated when exhausted)
    *   (7) trip-count:
    *         tc: defined by a, taken-test in b
    */
   struct InductionInfo : public ArenaObject<kArenaAllocInductionVarAnalysis> {
     InductionInfo(InductionClass ic,
                   InductionOp op,
                   InductionInfo* a,
                   InductionInfo* b,
                   HInstruction* f,
                   DataType::Type t)
         : induction_class(ic),
           operation(op),
           op_a(a),
           op_b(b),
           fetch(f),
           type(t) {}
     InductionClass induction_class;
     InductionOp operation;
     InductionInfo* op_a;
     InductionInfo* op_b;
     HInstruction* fetch;
     DataType::Type type;  // precision of operation
   };

   bool IsVisitedNode(HInstruction* instruction) const {
     return map_.find(instruction) != map_.end();
   }

   InductionInfo* CreateInvariantOp(InductionOp op, InductionInfo* a, InductionInfo* b) {
     DCHECK(((op != kNeg && a != nullptr) || (op == kNeg && a == nullptr)) && b != nullptr);
     return CreateSimplifiedInvariant(op, a, b);
   }

   InductionInfo* CreateInvariantFetch(HInstruction* f) {
     DCHECK(f != nullptr);
     return new (graph_->GetAllocator())
         InductionInfo(kInvariant, kFetch, nullptr, nullptr, f, f->GetType());
   }

   InductionInfo* CreateTripCount(InductionOp op,
                                  InductionInfo* a,
                                  InductionInfo* b,
                                  DataType::Type type) {
     DCHECK(a != nullptr && b != nullptr);
     return new (graph_->GetAllocator()) InductionInfo(kInvariant, op, a, b, nullptr, type);
   }

   InductionInfo* CreateInduction(InductionClass ic,
                                  InductionOp op,
                                  InductionInfo* a,
                                  InductionInfo* b,
                                  HInstruction* f,
                                  DataType::Type type) {
     DCHECK(a != nullptr && b != nullptr);
     return new (graph_->GetAllocator()) InductionInfo(ic, op, a, b, f, type);
   }

   // Methods for analysis.
   void VisitLoop(HLoopInformation* loop);
   void VisitNode(HLoopInformation* loop, HInstruction* instruction);
   uint32_t VisitDescendant(HLoopInformation* loop, HInstruction* instruction);
   void ClassifyTrivial(HLoopInformation* loop, HInstruction* instruction);
   void ClassifyNonTrivial(HLoopInformation* loop);
   InductionInfo* RotatePeriodicInduction(InductionInfo* induction, InductionInfo* last);

   // Transfer operations.
   InductionInfo* TransferPhi(HLoopInformation* loop,
                              HInstruction* phi,
                              size_t input_index,
                              size_t adjust_input_size);
   InductionInfo* TransferAddSub(InductionInfo* a, InductionInfo* b, InductionOp op);
   InductionInfo* TransferNeg(InductionInfo* a);
   InductionInfo* TransferMul(InductionInfo* a, InductionInfo* b);
   InductionInfo* TransferConversion(InductionInfo* a, DataType::Type from, DataType::Type to);

   // Solvers.
   InductionInfo* SolvePhi(HInstruction* phi, size_t input_index, size_t adjust_input_size);
   InductionInfo* SolvePhiAllInputs(HLoopInformation* loop,
                                    HInstruction* entry_phi,
                                    HInstruction* phi);
   InductionInfo* SolveAddSub(HLoopInformation* loop,
                              HInstruction* entry_phi,
                              HInstruction* instruction,
                              HInstruction* x,
                              HInstruction* y,
                              InductionOp op,
                              bool is_first_call);  // possibly swaps x and y to try again
   InductionInfo* SolveOp(HLoopInformation* loop,
                          HInstruction* entry_phi,
                          HInstruction* instruction,
                          HInstruction* x,
                          HInstruction* y,
                          InductionOp op);
   InductionInfo* SolveTest(HLoopInformation* loop,
                            HInstruction* entry_phi,
                            HInstruction* instruction,
                            int64_t oppositive_value);
   InductionInfo* SolveConversion(HLoopInformation* loop,
                                  HInstruction* entry_phi,
                                  HTypeConversion* conversion);

   //
   // Loop trip count analysis methods.
   //

   // Trip count information.
   void VisitControl(HLoopInformation* loop);
   void VisitCondition(HLoopInformation* loop,
                       HBasicBlock* body,
                       InductionInfo* a,
                       InductionInfo* b,
                       DataType::Type type,
                       IfCondition cmp);
   void VisitTripCount(HLoopInformation* loop,
                       InductionInfo* lower_expr,
                       InductionInfo* upper_expr,
                       InductionInfo* stride,
                       int64_t stride_value,
                       DataType::Type type,
                       IfCondition cmp);
   bool IsTaken(InductionInfo* lower_expr, InductionInfo* upper_expr, IfCondition cmp);
   bool IsFinite(InductionInfo* upper_expr,
                 int64_t stride_value,
                 DataType::Type type,
                 IfCondition cmp);
   bool FitsNarrowerControl(InductionInfo* lower_expr,
                            InductionInfo* upper_expr,
                            int64_t stride_value,
                            DataType::Type type,
                            IfCondition cmp);
   bool RewriteBreakLoop(HLoopInformation* loop,
                         HBasicBlock* body,
                         int64_t stride_value,
                         DataType::Type type);

   //
   // Helper methods.
   //

   // Assign and lookup.
   void AssignInfo(HLoopInformation* loop, HInstruction* instruction, InductionInfo* info);
   InductionInfo* LookupInfo(HLoopInformation* loop, HInstruction* instruction);
   InductionInfo* CreateConstant(int64_t value, DataType::Type type);
   InductionInfo* CreateSimplifiedInvariant(InductionOp op, InductionInfo* a, InductionInfo* b);
   HInstruction* GetShiftConstant(HLoopInformation* loop,
                                  HInstruction* instruction,
                                  InductionInfo* initial);
   void AssignCycle(HPhi* phi);
   ArenaSet<HInstruction*>* LookupCycle(HPhi* phi);

   // Constants.
   bool IsExact(InductionInfo* info, /*out*/ int64_t* value);
   bool IsAtMost(InductionInfo* info, /*out*/ int64_t* value);
   bool IsAtLeast(InductionInfo* info, /*out*/ int64_t* value);

   // Helpers.
   static bool IsNarrowingLinear(InductionInfo* info);
   static bool InductionEqual(InductionInfo* info1, InductionInfo* info2);
   static std::string FetchToString(HInstruction* fetch);
   static std::string InductionToString(InductionInfo* info);

   // TODO: fine tune the following data structures, only keep relevant data.

   // Temporary book-keeping during the analysis.
   uint32_t global_depth_;
   ArenaVector<HInstruction*> stack_;
   ArenaSafeMap<HInstruction*, NodeInfo> map_;
   ArenaVector<HInstruction*> scc_;
   ArenaSafeMap<HInstruction*, InductionInfo*> cycle_;
   DataType::Type type_;

   /**
    * Maintains the results of the analysis as a mapping from loops to a mapping from instructions
    * to the induction information for that instruction in that loop.
    */
   ArenaSafeMap<HLoopInformation*, ArenaSafeMap<HInstruction*, InductionInfo*>> induction_;

   /**
    * Preserves induction cycle information for each loop-phi.
    */
   ArenaSafeMap<HPhi*, ArenaSet<HInstruction*>> cycles_;

   friend class InductionVarAnalysisTest;
   friend class InductionVarRange;
   friend class InductionVarRangeTest;

   DISALLOW_COPY_AND_ASSIGN(HInductionVarAnalysis);
 };

 }  // namespace art

 #endif  // ART_COMPILER_OPTIMIZING_INDUCTION_VAR_ANALYSIS_H_
	/*
	* Copyright (C) 2015 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_INDUCTION_VAR_ANALYSIS_H_
	#define ART_COMPILER_OPTIMIZING_INDUCTION_VAR_ANALYSIS_H_

	#include <string>

	#include "nodes.h"
	#include "optimization.h"

	namespace art {

	/**
	* Induction variable analysis. This class does not have a direct public API.
	* Instead, the results of induction variable analysis can be queried through
	* friend classes, such as InductionVarRange.
	*
	* The analysis implementation is based on the paper by M. Gerlek et al.
	* "Beyond Induction Variables: Detecting and Classifying Sequences Using a Demand-Driven SSA Form"
	* (ACM Transactions on Programming Languages and Systems, Volume 17 Issue 1, Jan. 1995).
	*/
	class HInductionVarAnalysis : public HOptimization {
	public:
	explicit HInductionVarAnalysis(HGraph* graph, const char* name = kInductionPassName);

	bool Run() override;

	static constexpr const char* kInductionPassName = "induction_var_analysis";

	private:
	struct NodeInfo {
	explicit NodeInfo(uint32_t d) : depth(d), done(false) {}
	uint32_t depth;
	bool done;
	};

	enum InductionClass {
	kInvariant,
	kLinear,
	kPolynomial,
	kGeometric,
	kWrapAround,
	kPeriodic
	};

	enum InductionOp {
	// Operations.
	kNop,
	kAdd,
	kSub,
	kNeg,
	kMul,
	kDiv,
	kRem,
	kXor,
	kFetch,
	// Trip-counts.
	kTripCountInLoop, // valid in full loop; loop is finite
	kTripCountInBody, // valid in body only; loop is finite
	kTripCountInLoopUnsafe, // valid in full loop; loop may be infinite
	kTripCountInBodyUnsafe, // valid in body only; loop may be infinite
	// Comparisons for trip-count tests.
	kLT,
	kLE,
	kGT,
	kGE
	};

	/**
	* Defines a detected induction as:
	* (1) invariant:
	* op: a + b, a - b, -b, a * b, a / b, a % b, a ^ b, fetch
	* (2) linear:
	* nop: a * i + b
	* (3) polynomial:
	* nop: sum_lt(a) + b, for linear a
	* (4) geometric:
	* op: a * fetch^i + b, a * fetch^-i + b
	* (5) wrap-around
	* nop: a, then defined by b
	* (6) periodic
	* nop: a, then defined by b (repeated when exhausted)
	* (7) trip-count:
	* tc: defined by a, taken-test in b
	*/
	struct InductionInfo : public ArenaObject<kArenaAllocInductionVarAnalysis> {
	InductionInfo(InductionClass ic,
	InductionOp op,
	InductionInfo* a,
	InductionInfo* b,
	HInstruction* f,
	DataType::Type t)
	: induction_class(ic),
	operation(op),
	op_a(a),
	op_b(b),
	fetch(f),
	type(t) {}
	InductionClass induction_class;
	InductionOp operation;
	InductionInfo* op_a;
	InductionInfo* op_b;
	HInstruction* fetch;
	DataType::Type type; // precision of operation
	};

	bool IsVisitedNode(HInstruction* instruction) const {
	return map_.find(instruction) != map_.end();
	}

	InductionInfo* CreateInvariantOp(InductionOp op, InductionInfo* a, InductionInfo* b) {
	DCHECK(((op != kNeg && a != nullptr) \|\| (op == kNeg && a == nullptr)) && b != nullptr);
	return CreateSimplifiedInvariant(op, a, b);
	}

	InductionInfo* CreateInvariantFetch(HInstruction* f) {
	DCHECK(f != nullptr);
	return new (graph_->GetAllocator())
	InductionInfo(kInvariant, kFetch, nullptr, nullptr, f, f->GetType());
	}

	InductionInfo* CreateTripCount(InductionOp op,
	InductionInfo* a,
	InductionInfo* b,
	DataType::Type type) {
	DCHECK(a != nullptr && b != nullptr);
	return new (graph_->GetAllocator()) InductionInfo(kInvariant, op, a, b, nullptr, type);
	}

	InductionInfo* CreateInduction(InductionClass ic,
	InductionOp op,
	InductionInfo* a,
	InductionInfo* b,
	HInstruction* f,
	DataType::Type type) {
	DCHECK(a != nullptr && b != nullptr);
	return new (graph_->GetAllocator()) InductionInfo(ic, op, a, b, f, type);
	}

	// Methods for analysis.
	void VisitLoop(HLoopInformation* loop);
	void VisitNode(HLoopInformation* loop, HInstruction* instruction);
	uint32_t VisitDescendant(HLoopInformation* loop, HInstruction* instruction);
	void ClassifyTrivial(HLoopInformation* loop, HInstruction* instruction);
	void ClassifyNonTrivial(HLoopInformation* loop);
	InductionInfo* RotatePeriodicInduction(InductionInfo* induction, InductionInfo* last);

	// Transfer operations.
	InductionInfo* TransferPhi(HLoopInformation* loop,
	HInstruction* phi,
	size_t input_index,
	size_t adjust_input_size);
	InductionInfo* TransferAddSub(InductionInfo* a, InductionInfo* b, InductionOp op);
	InductionInfo* TransferNeg(InductionInfo* a);
	InductionInfo* TransferMul(InductionInfo* a, InductionInfo* b);
	InductionInfo* TransferConversion(InductionInfo* a, DataType::Type from, DataType::Type to);

	// Solvers.
	InductionInfo* SolvePhi(HInstruction* phi, size_t input_index, size_t adjust_input_size);
	InductionInfo* SolvePhiAllInputs(HLoopInformation* loop,
	HInstruction* entry_phi,
	HInstruction* phi);
	InductionInfo* SolveAddSub(HLoopInformation* loop,
	HInstruction* entry_phi,
	HInstruction* instruction,
	HInstruction* x,
	HInstruction* y,
	InductionOp op,
	bool is_first_call); // possibly swaps x and y to try again
	InductionInfo* SolveOp(HLoopInformation* loop,
	HInstruction* entry_phi,
	HInstruction* instruction,
	HInstruction* x,
	HInstruction* y,
	InductionOp op);
	InductionInfo* SolveTest(HLoopInformation* loop,
	HInstruction* entry_phi,
	HInstruction* instruction,
	int64_t oppositive_value);
	InductionInfo* SolveConversion(HLoopInformation* loop,
	HInstruction* entry_phi,
	HTypeConversion* conversion);

	//
	// Loop trip count analysis methods.
	//

	// Trip count information.
	void VisitControl(HLoopInformation* loop);
	void VisitCondition(HLoopInformation* loop,
	HBasicBlock* body,
	InductionInfo* a,
	InductionInfo* b,
	DataType::Type type,
	IfCondition cmp);
	void VisitTripCount(HLoopInformation* loop,
	InductionInfo* lower_expr,
	InductionInfo* upper_expr,
	InductionInfo* stride,
	int64_t stride_value,
	DataType::Type type,
	IfCondition cmp);
	bool IsTaken(InductionInfo* lower_expr, InductionInfo* upper_expr, IfCondition cmp);
	bool IsFinite(InductionInfo* upper_expr,
	int64_t stride_value,
	DataType::Type type,
	IfCondition cmp);
	bool FitsNarrowerControl(InductionInfo* lower_expr,
	InductionInfo* upper_expr,
	int64_t stride_value,
	DataType::Type type,
	IfCondition cmp);
	bool RewriteBreakLoop(HLoopInformation* loop,
	HBasicBlock* body,
	int64_t stride_value,
	DataType::Type type);

	//
	// Helper methods.
	//

	// Assign and lookup.
	void AssignInfo(HLoopInformation* loop, HInstruction* instruction, InductionInfo* info);
	InductionInfo* LookupInfo(HLoopInformation* loop, HInstruction* instruction);
	InductionInfo* CreateConstant(int64_t value, DataType::Type type);
	InductionInfo* CreateSimplifiedInvariant(InductionOp op, InductionInfo* a, InductionInfo* b);
	HInstruction* GetShiftConstant(HLoopInformation* loop,
	HInstruction* instruction,
	InductionInfo* initial);
	void AssignCycle(HPhi* phi);
	ArenaSet<HInstruction> LookupCycle(HPhi* phi);

	// Constants.
	bool IsExact(InductionInfo* info, /out/ int64_t* value);
	bool IsAtMost(InductionInfo* info, /out/ int64_t* value);
	bool IsAtLeast(InductionInfo* info, /out/ int64_t* value);

	// Helpers.
	static bool IsNarrowingLinear(InductionInfo* info);
	static bool InductionEqual(InductionInfo* info1, InductionInfo* info2);
	static std::string FetchToString(HInstruction* fetch);
	static std::string InductionToString(InductionInfo* info);

	// TODO: fine tune the following data structures, only keep relevant data.

	// Temporary book-keeping during the analysis.
	uint32_t global_depth_;
	ArenaVector<HInstruction*> stack_;
	ArenaSafeMap<HInstruction*, NodeInfo> map_;
	ArenaVector<HInstruction*> scc_;
	ArenaSafeMap<HInstruction, InductionInfo> cycle_;
	DataType::Type type_;

	/**
	* Maintains the results of the analysis as a mapping from loops to a mapping from instructions
	* to the induction information for that instruction in that loop.
	*/
	ArenaSafeMap<HLoopInformation, ArenaSafeMap<HInstruction, InductionInfo*>> induction_;

	/**
	* Preserves induction cycle information for each loop-phi.
	*/
	ArenaSafeMap<HPhi, ArenaSet<HInstruction>> cycles_;

	friend class InductionVarAnalysisTest;
	friend class InductionVarRange;
	friend class InductionVarRangeTest;

	DISALLOW_COPY_AND_ASSIGN(HInductionVarAnalysis);
	};

	} // namespace art

	#endif // ART_COMPILER_OPTIMIZING_INDUCTION_VAR_ANALYSIS_H_