instruction_simplifier.cc revision 01fcc9ee556f98d0163cc9b524e989760826926f 
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  void VisitTypeConversion(HTypeConversion* instruction) OVERRIDE;
30};
31
32void InstructionSimplifier::Run() {
33  InstructionSimplifierVisitor visitor(graph_);
34  visitor.VisitInsertionOrder();
35}
36
37void InstructionSimplifierVisitor::VisitSuspendCheck(HSuspendCheck* check) {
38  HBasicBlock* block = check->GetBlock();
39  // Currently always keep the suspend check at entry.
40  if (block->IsEntryBlock()) return;
41
42  // Currently always keep suspend checks at loop entry.
43  if (block->IsLoopHeader() && block->GetFirstInstruction() == check) {
44    DCHECK(block->GetLoopInformation()->GetSuspendCheck() == check);
45    return;
46  }
47
48  // Remove the suspend check that was added at build time for the baseline
49  // compiler.
50  block->RemoveInstruction(check);
51}
52
53void InstructionSimplifierVisitor::VisitEqual(HEqual* equal) {
54  HInstruction* input1 = equal->InputAt(0);
55  HInstruction* input2 = equal->InputAt(1);
56  if (input1->GetType() == Primitive::kPrimBoolean && input2->IsIntConstant()) {
57    if (input2->AsIntConstant()->GetValue() == 1) {
58      // Replace (bool_value == 1) with bool_value
59      equal->ReplaceWith(equal->InputAt(0));
60      equal->GetBlock()->RemoveInstruction(equal);
61    } else {
62      // Replace (bool_value == 0) with !bool_value
63      DCHECK_EQ(input2->AsIntConstant()->GetValue(), 0);
64      equal->GetBlock()->ReplaceAndRemoveInstructionWith(
65          equal, new (GetGraph()->GetArena()) HNot(Primitive::kPrimBoolean, input1));
66    }
67  }
68}
69
70void InstructionSimplifierVisitor::VisitArraySet(HArraySet* instruction) {
71  HInstruction* value = instruction->GetValue();
72  if (value->GetType() != Primitive::kPrimNot) return;
73
74  if (value->IsArrayGet()) {
75    if (value->AsArrayGet()->GetArray() == instruction->GetArray()) {
76      // If the code is just swapping elements in the array, no need for a type check.
77      instruction->ClearNeedsTypeCheck();
78    }
79  }
80}
81
82void InstructionSimplifierVisitor::VisitTypeConversion(HTypeConversion* instruction) {
83  if (instruction->GetResultType() == instruction->GetInputType()) {
84    // Remove the instruction if it's converting to the same type.
85    instruction->ReplaceWith(instruction->GetInput());
86    instruction->GetBlock()->RemoveInstruction(instruction);
87  }
88}
89
90}  // namespace art
91