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98 lines
2.8 KiB
98 lines
2.8 KiB
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_COMPILER_OPTIMIZING_COMMON_DOMINATOR_H_
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#define ART_COMPILER_OPTIMIZING_COMMON_DOMINATOR_H_
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#include "nodes.h"
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namespace art {
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// Helper class for finding common dominators of two or more blocks in a graph.
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// The domination information of a graph must not be modified while there is
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// a CommonDominator object as it's internal state could become invalid.
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class CommonDominator {
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public:
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// Convenience function to find the common dominator of 2 blocks.
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static HBasicBlock* ForPair(HBasicBlock* block1, HBasicBlock* block2) {
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CommonDominator finder(block1);
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finder.Update(block2);
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return finder.Get();
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}
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// Create a finder starting with a given block.
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explicit CommonDominator(HBasicBlock* block)
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: dominator_(block), chain_length_(ChainLength(block)) {
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}
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// Update the common dominator with another block.
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void Update(HBasicBlock* block) {
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DCHECK(block != nullptr);
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if (dominator_ == nullptr) {
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dominator_ = block;
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chain_length_ = ChainLength(block);
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return;
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}
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HBasicBlock* block2 = dominator_;
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DCHECK(block2 != nullptr);
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if (block == block2) {
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return;
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}
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size_t chain_length = ChainLength(block);
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size_t chain_length2 = chain_length_;
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// Equalize the chain lengths
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for ( ; chain_length > chain_length2; --chain_length) {
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block = block->GetDominator();
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DCHECK(block != nullptr);
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}
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for ( ; chain_length2 > chain_length; --chain_length2) {
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block2 = block2->GetDominator();
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DCHECK(block2 != nullptr);
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}
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// Now run up the chain until we hit the common dominator.
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while (block != block2) {
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--chain_length;
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block = block->GetDominator();
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DCHECK(block != nullptr);
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block2 = block2->GetDominator();
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DCHECK(block2 != nullptr);
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}
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dominator_ = block;
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chain_length_ = chain_length;
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}
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HBasicBlock* Get() const {
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return dominator_;
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}
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private:
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static size_t ChainLength(HBasicBlock* block) {
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size_t result = 0;
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while (block != nullptr) {
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++result;
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block = block->GetDominator();
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}
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return result;
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}
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HBasicBlock* dominator_;
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size_t chain_length_;
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};
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} // namespace art
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#endif // ART_COMPILER_OPTIMIZING_COMMON_DOMINATOR_H_
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