1 // Copyright (c) 2017 Google Inc.
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/redundancy_elimination.h"
16
17 #include "source/opt/value_number_table.h"
18
19 namespace spvtools {
20 namespace opt {
21
Process()22 Pass::Status RedundancyEliminationPass::Process() {
23 bool modified = false;
24 ValueNumberTable vnTable(context());
25
26 for (auto& func : *get_module()) {
27 if (func.IsDeclaration()) {
28 continue;
29 }
30
31 // Build the dominator tree for this function. It is how the code is
32 // traversed.
33 DominatorTree& dom_tree =
34 context()->GetDominatorAnalysis(&func)->GetDomTree();
35
36 // Keeps track of all ids that contain a given value number. We keep
37 // track of multiple values because they could have the same value, but
38 // different decorations.
39 std::map<uint32_t, uint32_t> value_to_ids;
40
41 if (EliminateRedundanciesFrom(dom_tree.GetRoot(), vnTable, value_to_ids)) {
42 modified = true;
43 }
44 }
45 return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
46 }
47
EliminateRedundanciesFrom(DominatorTreeNode * bb,const ValueNumberTable & vnTable,std::map<uint32_t,uint32_t> value_to_ids)48 bool RedundancyEliminationPass::EliminateRedundanciesFrom(
49 DominatorTreeNode* bb, const ValueNumberTable& vnTable,
50 std::map<uint32_t, uint32_t> value_to_ids) {
51 bool modified = EliminateRedundanciesInBB(bb->bb_, vnTable, &value_to_ids);
52
53 for (auto dominated_bb : bb->children_) {
54 modified |= EliminateRedundanciesFrom(dominated_bb, vnTable, value_to_ids);
55 }
56
57 return modified;
58 }
59 } // namespace opt
60 } // namespace spvtools
61