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
21 namespace spvtools {
22 namespace opt {
23
CommonDominator(BasicBlock * b1,BasicBlock * b2) const24 BasicBlock* 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
Dominates(Instruction * a,Instruction * b) const42 bool 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 const Instruction* current = a;
59 const Instruction* other = b;
60
61 if (tree_.IsPostDominator()) {
62 std::swap(current, other);
63 }
64
65 // We handle OpLabel instructions explicitly since they are not stored in the
66 // instruction list.
67 if (current->opcode() == SpvOpLabel) {
68 return true;
69 }
70
71 while ((current = current->NextNode())) {
72 if (current == other) {
73 return true;
74 }
75 }
76
77 return false;
78 }
79
80 } // namespace opt
81 } // namespace spvtools
82