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_BUILDER_H_
18#define ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
19
20#include "nodes.h"
21#include "optimization.h"
22
23namespace art {
24
25static constexpr int kDefaultNumberOfLoops = 2;
26
27/**
28 * Transforms a graph into SSA form. The liveness guarantees of
29 * this transformation are listed below. A DEX register
30 * being killed means its value at a given position in the code
31 * will not be available to its environment uses. A merge in the
32 * following text is materialized as a `HPhi`.
33 *
34 * (a) Dex registers that do not require merging (that is, they do not
35 *     have different values at a join block) are available to all their
36 *     environment uses. Note that it does not imply the instruction will
37 *     have a physical location after register allocation. See the
38 *     SsaLivenessAnalysis phase.
39 *
40 * (b) Dex registers that require merging, and the merging gives
41 *     incompatible types, will be killed for environment uses of that merge.
42 *
43 * (c) When the `debuggable` flag is passed to the compiler, Dex registers
44 *     that require merging and have a proper type after the merge, are
45 *     available to all their environment uses. If the `debuggable` flag
46 *     is not set, values of Dex registers only used by environments
47 *     are killed.
48 */
49class SsaBuilder : public HGraphVisitor {
50 public:
51  explicit SsaBuilder(HGraph* graph)
52      : HGraphVisitor(graph),
53        current_locals_(nullptr),
54        loop_headers_(graph->GetArena(), kDefaultNumberOfLoops),
55        locals_for_(graph->GetArena(), graph->GetBlocks().Size()) {
56    locals_for_.SetSize(graph->GetBlocks().Size());
57  }
58
59  void BuildSsa();
60
61  GrowableArray<HInstruction*>* GetLocalsFor(HBasicBlock* block) {
62    GrowableArray<HInstruction*>* locals = locals_for_.Get(block->GetBlockId());
63    if (locals == nullptr) {
64      locals = new (GetGraph()->GetArena()) GrowableArray<HInstruction*>(
65          GetGraph()->GetArena(), GetGraph()->GetNumberOfVRegs());
66      locals->SetSize(GetGraph()->GetNumberOfVRegs());
67      locals_for_.Put(block->GetBlockId(), locals);
68    }
69    return locals;
70  }
71
72  HInstruction* ValueOfLocal(HBasicBlock* block, size_t local);
73
74  void VisitBasicBlock(HBasicBlock* block);
75  void VisitLoadLocal(HLoadLocal* load);
76  void VisitStoreLocal(HStoreLocal* store);
77  void VisitInstruction(HInstruction* instruction);
78  void VisitTemporary(HTemporary* instruction);
79
80  static HInstruction* GetFloatOrDoubleEquivalent(HInstruction* user,
81                                                  HInstruction* instruction,
82                                                  Primitive::Type type);
83
84  static HInstruction* GetReferenceTypeEquivalent(HInstruction* instruction);
85
86  static constexpr const char* kSsaBuilderPassName = "ssa_builder";
87
88 private:
89  void FixNullConstantType();
90  void EquivalentPhisCleanup();
91
92  static HFloatConstant* GetFloatEquivalent(HIntConstant* constant);
93  static HDoubleConstant* GetDoubleEquivalent(HLongConstant* constant);
94  static HPhi* GetFloatDoubleOrReferenceEquivalentOfPhi(HPhi* phi, Primitive::Type type);
95
96  // Locals for the current block being visited.
97  GrowableArray<HInstruction*>* current_locals_;
98
99  // Keep track of loop headers found. The last phase of the analysis iterates
100  // over these blocks to set the inputs of their phis.
101  GrowableArray<HBasicBlock*> loop_headers_;
102
103  // HEnvironment for each block.
104  GrowableArray<GrowableArray<HInstruction*>*> locals_for_;
105
106  DISALLOW_COPY_AND_ASSIGN(SsaBuilder);
107};
108
109}  // namespace art
110
111#endif  // ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
112