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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_RANGE_H_
#define ART_COMPILER_OPTIMIZING_INDUCTION_VAR_RANGE_H_
#include "induction_var_analysis.h"
namespace art {
/**
* This class implements induction variable based range analysis on expressions within loops.
* It takes the results of induction variable analysis in the constructor and provides a public
* API to obtain a conservative lower and upper bound value on each instruction in the HIR.
*
* For example, given a linear induction 2 * i + x where 0 <= i <= 10, range analysis yields lower
* bound value x and upper bound value x + 20 for the expression, thus, the range [x, x + 20].
*/
class InductionVarRange {
public:
/*
* A value that can be represented as "a * instruction + b" for 32-bit constants, where
* Value(INT_MIN) and Value(INT_MAX) denote an unknown lower and upper bound, respectively.
* Although range analysis could yield more complex values, the format is sufficiently powerful
* to represent useful cases and feeds directly into optimizations like bounds check elimination.
*/
struct Value {
Value(HInstruction* i, int32_t a, int32_t b)
: instruction(a != 0 ? i : nullptr),
a_constant(a),
b_constant(b) {}
explicit Value(int32_t b) : Value(nullptr, 0, b) {}
HInstruction* instruction;
int32_t a_constant;
int32_t b_constant;
};
explicit InductionVarRange(HInductionVarAnalysis* induction);
/**
* Given a context denoted by the first instruction, returns a,
* possibly conservative, lower bound on the instruction's value.
*/
Value GetMinInduction(HInstruction* context, HInstruction* instruction);
/**
* Given a context denoted by the first instruction, returns a,
* possibly conservative, upper bound on the instruction's value.
*/
Value GetMaxInduction(HInstruction* context, HInstruction* instruction);
private:
//
// Private helper methods.
//
HInductionVarAnalysis::InductionInfo* GetTripCount(HLoopInformation* loop,
HInstruction* context);
static Value GetFetch(HInstruction* instruction,
HInductionVarAnalysis::InductionInfo* trip,
int32_t fail_value);
static Value GetMin(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip);
static Value GetMax(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip);
static Value GetMul(HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
int32_t fail_value);
static Value GetDiv(HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
int32_t fail_value);
static Value AddValue(Value v1, Value v2, int32_t fail_value);
static Value SubValue(Value v1, Value v2, int32_t fail_value);
static Value MulValue(Value v1, Value v2, int32_t fail_value);
static Value DivValue(Value v1, Value v2, int32_t fail_value);
static Value MinValue(Value v1, Value v2);
static Value MaxValue(Value v1, Value v2);
/** Results of prior induction variable analysis. */
HInductionVarAnalysis *induction_analysis_;
friend class HInductionVarAnalysis;
friend class InductionVarRangeTest;
DISALLOW_COPY_AND_ASSIGN(InductionVarRange);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_INDUCTION_VAR_RANGE_H_
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