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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 "nodes.h"
#include "utils/growable_array.h"
namespace art {
void HGraph::AddBlock(HBasicBlock* block) {
block->set_block_id(blocks_.Size());
blocks_.Add(block);
}
void HGraph::FindBackEdges(ArenaBitVector* visited) const {
ArenaBitVector visiting(arena_, blocks_.Size(), false);
VisitBlockForBackEdges(entry_block_, visited, &visiting);
}
void HGraph::RemoveDeadBlocks(const ArenaBitVector& visited) const {
for (size_t i = 0; i < blocks_.Size(); i++) {
if (!visited.IsBitSet(i)) {
HBasicBlock* block = blocks_.Get(i);
for (size_t j = 0; j < block->successors()->Size(); j++) {
block->successors()->Get(j)->RemovePredecessor(block);
}
}
}
}
void HGraph::VisitBlockForBackEdges(HBasicBlock* block,
ArenaBitVector* visited,
ArenaBitVector* visiting) const {
int id = block->block_id();
if (visited->IsBitSet(id)) return;
visited->SetBit(id);
visiting->SetBit(id);
for (size_t i = 0; i < block->successors()->Size(); i++) {
HBasicBlock* successor = block->successors()->Get(i);
if (visiting->IsBitSet(successor->block_id())) {
successor->AddBackEdge(block);
} else {
VisitBlockForBackEdges(successor, visited, visiting);
}
}
visiting->ClearBit(id);
}
void HGraph::BuildDominatorTree() {
ArenaBitVector visited(arena_, blocks_.Size(), false);
// (1) Find the back edges in the graph doing a DFS traversal.
FindBackEdges(&visited);
// (2) Remove blocks not visited during the initial DFS.
// Step (3) requires dead blocks to be removed from the
// predecessors list of live blocks.
RemoveDeadBlocks(visited);
// (3) Compute the immediate dominator of each block. We visit
// the successors of a block only when all its forward branches
// have been processed.
GrowableArray<size_t> visits(arena_, blocks_.Size());
visits.SetSize(blocks_.Size());
dominator_order_.Add(entry_block_);
for (size_t i = 0; i < entry_block_->successors()->Size(); i++) {
VisitBlockForDominatorTree(entry_block_->successors()->Get(i), entry_block_, &visits);
}
}
HBasicBlock* HGraph::FindCommonDominator(HBasicBlock* first, HBasicBlock* second) const {
ArenaBitVector visited(arena_, blocks_.Size(), false);
// Walk the dominator tree of the first block and mark the visited blocks.
while (first != nullptr) {
visited.SetBit(first->block_id());
first = first->dominator();
}
// Walk the dominator tree of the second block until a marked block is found.
while (second != nullptr) {
if (visited.IsBitSet(second->block_id())) {
return second;
}
second = second->dominator();
}
LOG(ERROR) << "Could not find common dominator";
return nullptr;
}
void HGraph::VisitBlockForDominatorTree(HBasicBlock* block,
HBasicBlock* predecessor,
GrowableArray<size_t>* visits) {
if (block->dominator() == nullptr) {
block->set_dominator(predecessor);
} else {
block->set_dominator(FindCommonDominator(block->dominator(), predecessor));
}
visits->Increment(block->block_id());
// Once all the forward edges have been visited, we know the immediate
// dominator of the block. We can then start visiting its successors.
if (visits->Get(block->block_id()) ==
block->predecessors()->Size() - block->NumberOfBackEdges()) {
dominator_order_.Add(block);
for (size_t i = 0; i < block->successors()->Size(); i++) {
VisitBlockForDominatorTree(block->successors()->Get(i), block, visits);
}
}
}
void HBasicBlock::AddInstruction(HInstruction* instruction) {
instruction->set_block(this);
instruction->set_id(graph()->GetNextInstructionId());
if (first_instruction_ == nullptr) {
DCHECK(last_instruction_ == nullptr);
first_instruction_ = last_instruction_ = instruction;
} else {
last_instruction_->next_ = instruction;
instruction->previous_ = last_instruction_;
last_instruction_ = instruction;
}
for (int i = 0; i < instruction->InputCount(); i++) {
instruction->InputAt(i)->AddUse(instruction);
}
}
#define DEFINE_ACCEPT(name) \
void H##name::Accept(HGraphVisitor* visitor) { \
visitor->Visit##name(this); \
}
FOR_EACH_INSTRUCTION(DEFINE_ACCEPT)
#undef DEFINE_ACCEPT
void HGraphVisitor::VisitInsertionOrder() {
const GrowableArray<HBasicBlock*>* blocks = graph_->blocks();
for (size_t i = 0 ; i < blocks->Size(); i++) {
VisitBasicBlock(blocks->Get(i));
}
}
void HGraphVisitor::VisitBasicBlock(HBasicBlock* block) {
for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
it.Current()->Accept(this);
}
}
} // namespace art
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