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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.
*/
// This optimization recognizes two common patterns:
// (a) Boolean selection: Casting a boolean to an integer or negating it is
// carried out with an If statement selecting from zero/one integer
// constants. Because Boolean values are represented as zero/one, the
// pattern can be replaced with the condition instruction itself or its
// negation, depending on the layout.
// (b) Negated condition: Instruction simplifier may replace an If's condition
// with a boolean value. If this value is the result of a Boolean negation,
// the true/false branches can be swapped and negation removed.
// Example: Negating a boolean value
// B1:
// z1 ParameterValue
// i2 IntConstant 0
// i3 IntConstant 1
// v4 Goto B2
// B2:
// z5 NotEquals [ z1 i2 ]
// v6 If [ z5 ] then B3 else B4
// B3:
// v7 Goto B5
// B4:
// v8 Goto B5
// B5:
// i9 Phi [ i3 i2 ]
// v10 Return [ i9 ]
// turns into
// B1:
// z1 ParameterValue
// i2 IntConstant 0
// v4 Goto B2
// B2:
// z11 Equals [ z1 i2 ]
// v10 Return [ z11 ]
// B3, B4, B5: removed
// Note: in order to recognize empty blocks, this optimization must be run
// after the instruction simplifier has removed redundant suspend checks.
#ifndef ART_COMPILER_OPTIMIZING_BOOLEAN_SIMPLIFIER_H_
#define ART_COMPILER_OPTIMIZING_BOOLEAN_SIMPLIFIER_H_
#include "optimization.h"
namespace art {
class HBooleanSimplifier : public HOptimization {
public:
explicit HBooleanSimplifier(HGraph* graph)
: HOptimization(graph, true, kBooleanSimplifierPassName) {}
void Run() OVERRIDE;
static constexpr const char* kBooleanSimplifierPassName = "boolean_simplifier";
private:
void TryRemovingNegatedCondition(HBasicBlock* block);
void TryRemovingBooleanSelection(HBasicBlock* block);
DISALLOW_COPY_AND_ASSIGN(HBooleanSimplifier);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_BOOLEAN_SIMPLIFIER_H_
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