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// Copyright (c) 2018 Google LLC
//
// 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 "source/opt/dominator_analysis.h"
#include <unordered_set>
#include "source/opt/ir_context.h"
namespace spvtools {
namespace opt {
BasicBlock* DominatorAnalysisBase::CommonDominator(BasicBlock* b1,
BasicBlock* b2) const {
if (!b1 || !b2) return nullptr;
std::unordered_set<BasicBlock*> seen;
BasicBlock* block = b1;
while (block && seen.insert(block).second) {
block = ImmediateDominator(block);
}
block = b2;
while (block && !seen.count(block)) {
block = ImmediateDominator(block);
}
return block;
}
bool DominatorAnalysisBase::Dominates(Instruction* a, Instruction* b) const {
if (!a || !b) {
return false;
}
if (a == b) {
return true;
}
BasicBlock* bb_a = a->context()->get_instr_block(a);
BasicBlock* bb_b = b->context()->get_instr_block(b);
if (bb_a != bb_b) {
return tree_.Dominates(bb_a, bb_b);
}
const Instruction* current = a;
const Instruction* other = b;
if (tree_.IsPostDominator()) {
std::swap(current, other);
}
// We handle OpLabel instructions explicitly since they are not stored in the
// instruction list.
if (current->opcode() == spv::Op::OpLabel) {
return true;
}
while ((current = current->NextNode())) {
if (current == other) {
return true;
}
}
return false;
}
} // namespace opt
} // namespace spvtools
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