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#ifndef SOURCE_OPT_REDUNDANCY_ELIMINATION_H_
16#define SOURCE_OPT_REDUNDANCY_ELIMINATION_H_
17
18#include <map>
19
20#include "source/opt/ir_context.h"
21#include "source/opt/local_redundancy_elimination.h"
22#include "source/opt/pass.h"
23#include "source/opt/value_number_table.h"
24
25namespace spvtools {
26namespace opt {
27
28// This pass implements total redundancy elimination. This is the same as
29// local redundancy elimination except it looks across basic block boundaries.
30// An instruction, inst, is totally redundant if there is another instruction
31// that dominates inst, and also computes the same value.
32class RedundancyEliminationPass : public LocalRedundancyEliminationPass {
33 public:
34 const char* name() const override { return "redundancy-elimination"; }
35 Status Process() override;
36
37 protected:
38 // Removes for all total redundancies in the function starting at |bb|.
39 //
40 // |vnTable| must have computed a value number for every result id defined
41 // in the function containing |bb|.
42 //
43 // |value_to_ids| is a map from value number to ids. If {vn, id} is in
44 // |value_to_ids| then vn is the value number of id, and the defintion of id
45 // dominates |bb|.
46 //
47 // Returns true if at least one instruction is deleted.
48 bool EliminateRedundanciesFrom(DominatorTreeNode* bb,
49 const ValueNumberTable& vnTable,
50 std::map<uint32_t, uint32_t> value_to_ids);
51};
52
53} // namespace opt
54} // namespace spvtools
55
56#endif // SOURCE_OPT_REDUNDANCY_ELIMINATION_H_
57