1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_COMPILER_OPTIMIZING_SSA_PHI_ELIMINATION_H_
18#define ART_COMPILER_OPTIMIZING_SSA_PHI_ELIMINATION_H_
19
20#include "base/arena_containers.h"
21#include "nodes.h"
22#include "optimization.h"
23
24namespace art {
25
26/**
27 * Optimization phase that removes dead phis from the graph. Dead phis are unused
28 * phis, or phis only used by other phis.
29 */
30class SsaDeadPhiElimination : public HOptimization {
31 public:
32  explicit SsaDeadPhiElimination(HGraph* graph)
33      : HOptimization(graph, kSsaDeadPhiEliminationPassName),
34        worklist_(graph->GetArena()->Adapter(kArenaAllocSsaPhiElimination)) {
35    worklist_.reserve(kDefaultWorklistSize);
36  }
37
38  void Run() OVERRIDE;
39
40  void MarkDeadPhis();
41  void EliminateDeadPhis();
42
43  static constexpr const char* kSsaDeadPhiEliminationPassName = "dead_phi_elimination";
44
45 private:
46  ArenaVector<HPhi*> worklist_;
47
48  static constexpr size_t kDefaultWorklistSize = 8;
49
50  DISALLOW_COPY_AND_ASSIGN(SsaDeadPhiElimination);
51};
52
53/**
54 * Removes redundant phis that may have been introduced when doing SSA conversion.
55 * For example, when entering a loop, we create phis for all live registers. These
56 * registers might be updated with the same value, or not updated at all. We can just
57 * replace the phi with the value when entering the loop.
58 */
59class SsaRedundantPhiElimination : public HOptimization {
60 public:
61  explicit SsaRedundantPhiElimination(HGraph* graph)
62      : HOptimization(graph, kSsaRedundantPhiEliminationPassName),
63        worklist_(graph->GetArena()->Adapter(kArenaAllocSsaPhiElimination)) {
64    worklist_.reserve(kDefaultWorklistSize);
65  }
66
67  void Run() OVERRIDE;
68
69  static constexpr const char* kSsaRedundantPhiEliminationPassName = "redundant_phi_elimination";
70
71 private:
72  ArenaVector<HPhi*> worklist_;
73
74  static constexpr size_t kDefaultWorklistSize = 8;
75
76  DISALLOW_COPY_AND_ASSIGN(SsaRedundantPhiElimination);
77};
78
79}  // namespace art
80
81#endif  // ART_COMPILER_OPTIMIZING_SSA_PHI_ELIMINATION_H_
82