instruction_simplifier.cc revision 5e6916cea259897baaca019c5c7a5d05746306ed 
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#include "instruction_simplifier.h"
18
19namespace art {
20
21class InstructionSimplifierVisitor : public HGraphVisitor {
22 public:
23  explicit InstructionSimplifierVisitor(HGraph* graph) : HGraphVisitor(graph) {}
24
25 private:
26  void VisitSuspendCheck(HSuspendCheck* check) OVERRIDE;
27  void VisitEqual(HEqual* equal) OVERRIDE;
28  void VisitArraySet(HArraySet* equal) OVERRIDE;
29};
30
31void InstructionSimplifier::Run() {
32  InstructionSimplifierVisitor visitor(graph_);
33  visitor.VisitInsertionOrder();
34}
35
36void InstructionSimplifierVisitor::VisitSuspendCheck(HSuspendCheck* check) {
37  HBasicBlock* block = check->GetBlock();
38  // Currently always keep the suspend check at entry.
39  if (block->IsEntryBlock()) return;
40
41  // Currently always keep suspend checks at loop entry.
42  if (block->IsLoopHeader() && block->GetFirstInstruction() == check) {
43    DCHECK(block->GetLoopInformation()->GetSuspendCheck() == check);
44    return;
45  }
46
47  // Remove the suspend check that was added at build time for the baseline
48  // compiler.
49  block->RemoveInstruction(check);
50}
51
52void InstructionSimplifierVisitor::VisitEqual(HEqual* equal) {
53  HInstruction* input1 = equal->InputAt(0);
54  HInstruction* input2 = equal->InputAt(1);
55  if (input1->GetType() == Primitive::kPrimBoolean && input2->IsIntConstant()) {
56    if (input2->AsIntConstant()->GetValue() == 1) {
57      // Replace (bool_value == 1) with bool_value
58      equal->ReplaceWith(equal->InputAt(0));
59      equal->GetBlock()->RemoveInstruction(equal);
60    } else {
61      // Replace (bool_value == 0) with !bool_value
62      DCHECK_EQ(input2->AsIntConstant()->GetValue(), 0);
63      equal->GetBlock()->ReplaceAndRemoveInstructionWith(
64          equal, new (GetGraph()->GetArena()) HNot(Primitive::kPrimBoolean, input1));
65    }
66  }
67}
68
69void InstructionSimplifierVisitor::VisitArraySet(HArraySet* instruction) {
70  HInstruction* value = instruction->GetValue();
71  if (value->GetType() != Primitive::kPrimNot) return;
72
73  if (value->IsArrayGet()) {
74    if (value->AsArrayGet()->GetArray() == instruction->GetArray()) {
75      // If the code is just swapping elements in the array, no need for a type check.
76      instruction->ClearNeedsTypeCheck();
77    }
78  }
79}
80
81}  // namespace art
82