1// Copyright (c) 2018 Google LLC
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15#include "source/opt/dominator_analysis.h"
16
17#include <unordered_set>
18
19#include "source/opt/ir_context.h"
20
21namespace spvtools {
22namespace opt {
23
24BasicBlock* DominatorAnalysisBase::CommonDominator(BasicBlock* b1,
25 BasicBlock* b2) const {
26 if (!b1 || !b2) return nullptr;
27
28 std::unordered_set<BasicBlock*> seen;
29 BasicBlock* block = b1;
30 while (block && seen.insert(block).second) {
31 block = ImmediateDominator(block);
32 }
33
34 block = b2;
35 while (block && !seen.count(block)) {
36 block = ImmediateDominator(block);
37 }
38
39 return block;
40}
41
42bool DominatorAnalysisBase::Dominates(Instruction* a, Instruction* b) const {
43 if (!a || !b) {
44 return false;
45 }
46
47 if (a == b) {
48 return true;
49 }
50
51 BasicBlock* bb_a = a->context()->get_instr_block(a);
52 BasicBlock* bb_b = b->context()->get_instr_block(b);
53
54 if (bb_a != bb_b) {
55 return tree_.Dominates(bb_a, bb_b);
56 }
57
58 Instruction* current_inst = a;
59 while ((current_inst = current_inst->NextNode())) {
60 if (current_inst == b) {
61 return true;
62 }
63 }
64 return false;
65}
66
67} // namespace opt
68} // namespace spvtools
69