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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 "dead_code_elimination.h"
#include "base/bit_vector-inl.h"
namespace art {
void HDeadCodeElimination::Run() {
// Process basic blocks in post-order in the dominator tree, so that
// a dead instruction depending on another dead instruction is
// removed.
for (HPostOrderIterator b(*graph_); !b.Done(); b.Advance()) {
HBasicBlock* block = b.Current();
// Traverse this block's instructions in backward order and remove
// the unused ones.
HBackwardInstructionIterator i(block->GetInstructions());
// Skip the first iteration, as the last instruction of a block is
// a branching instruction.
DCHECK(i.Current()->IsControlFlow());
for (i.Advance(); !i.Done(); i.Advance()) {
HInstruction* inst = i.Current();
DCHECK(!inst->IsControlFlow());
if (!inst->HasSideEffects()
&& !inst->CanThrow()
&& !inst->IsSuspendCheck()
&& !inst->HasUses()) {
block->RemoveInstruction(inst);
}
}
}
}
} // namespace art
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