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/*
* 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);
void Run() OVERRIDE;
private:
static constexpr const char* kInductionPassName = "induction_var_analysis";
struct NodeInfo {
explicit NodeInfo(uint32_t d) : depth(d), done(false) {}
uint32_t depth;
bool done;
};
enum InductionClass {
kInvariant,
kLinear,
kWrapAround,
kPeriodic
};
enum InductionOp {
kNop, // no-operation: a true induction
kAdd,
kSub,
kNeg,
kMul,
kDiv,
kFetch
};
/**
* Defines a detected induction as:
* (1) invariant:
* operation: a + b, a - b, -b, a * b, a / b
* or:
* fetch: fetch from HIR
* (2) linear:
* nop: a * i + b
* (3) wrap-around
* nop: a, then defined by b
* (4) periodic
* nop: a, then defined by b (repeated when exhausted)
*/
struct InductionInfo : public ArenaObject<kArenaAllocMisc> {
InductionInfo(InductionClass ic,
InductionOp op,
InductionInfo* a,
InductionInfo* b,
HInstruction* f)
: induction_class(ic),
operation(op),
op_a(a),
op_b(b),
fetch(f) {}
InductionClass induction_class;
InductionOp operation;
InductionInfo* op_a;
InductionInfo* op_b;
HInstruction* fetch;
};
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_->GetArena()) InductionInfo(kInvariant, kFetch, nullptr, nullptr, f);
}
InductionInfo* CreateInduction(InductionClass ic, InductionInfo* a, InductionInfo* b) {
DCHECK(a != nullptr && b != nullptr);
return new (graph_->GetArena()) InductionInfo(ic, kNop, a, b, nullptr);
}
// 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);
// Transfer operations.
InductionInfo* TransferPhi(InductionInfo* a, InductionInfo* b);
InductionInfo* TransferAddSub(InductionInfo* a, InductionInfo* b, InductionOp op);
InductionInfo* TransferMul(InductionInfo* a, InductionInfo* b);
InductionInfo* TransferShl(InductionInfo* a, InductionInfo* b, Primitive::Type t);
InductionInfo* TransferNeg(InductionInfo* a);
// Solvers.
InductionInfo* SolvePhi(HLoopInformation* loop,
HInstruction* phi,
HInstruction* instruction);
InductionInfo* SolveAddSub(HLoopInformation* loop,
HInstruction* phi,
HInstruction* instruction,
HInstruction* x,
HInstruction* y,
InductionOp op,
bool is_first_call);
InductionInfo* RotatePeriodicInduction(InductionInfo* induction, InductionInfo* last);
// Assign and lookup.
void AssignInfo(HLoopInformation* loop, HInstruction* instruction, InductionInfo* info);
InductionInfo* LookupInfo(HLoopInformation* loop, HInstruction* instruction);
InductionInfo* CreateSimplifiedInvariant(InductionOp op, InductionInfo* a, InductionInfo* b);
// Helpers.
static bool InductionEqual(InductionInfo* info1, InductionInfo* info2);
static bool IsIntAndGet(InductionInfo* info, int64_t* value);
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_;
ArenaVector<HInstruction*> scc_;
ArenaSafeMap<HInstruction*, NodeInfo> map_;
ArenaSafeMap<HInstruction*, InductionInfo*> cycle_;
/**
* 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_;
friend class InductionVarAnalysisTest;
DISALLOW_COPY_AND_ASSIGN(HInductionVarAnalysis);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_INDUCTION_VAR_ANALYSIS_H_
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