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/*
* Copyright (C) 2014 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.
*/
#include "constant_folding.h"
namespace art {
void HConstantFolding::Run() {
// Process basic blocks in reverse post-order in the dominator tree,
// so that an instruction turned into a constant, used as input of
// another instruction, may possibly be used to turn that second
// instruction into a constant as well.
for (HReversePostOrderIterator it(*graph_); !it.Done(); it.Advance()) {
HBasicBlock* block = it.Current();
// Traverse this block's instructions in (forward) order and
// replace the ones that can be statically evaluated by a
// compile-time counterpart.
for (HInstructionIterator inst_it(block->GetInstructions());
!inst_it.Done(); inst_it.Advance()) {
HInstruction* inst = inst_it.Current();
if (inst->IsBinaryOperation()) {
// Constant folding: replace `op(a, b)' with a constant at
// compile time if `a' and `b' are both constants.
HConstant* constant =
inst->AsBinaryOperation()->TryStaticEvaluation();
if (constant != nullptr) {
inst->GetBlock()->ReplaceAndRemoveInstructionWith(inst, constant);
}
} else if (inst->IsUnaryOperation()) {
// Constant folding: replace `op(a)' with a constant at compile
// time if `a' is a constant.
HConstant* constant =
inst->AsUnaryOperation()->TryStaticEvaluation();
if (constant != nullptr) {
inst->GetBlock()->ReplaceAndRemoveInstructionWith(inst, constant);
}
}
}
}
}
} // namespace art
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