side_effects_analysis.cc revision fa6b93c4b69e6d7ddfa2a4ed0aff01b0608c5a3a 
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 "side_effects_analysis.h"
18
19namespace art {
20
21void SideEffectsAnalysis::Run() {
22  // Inlining might have created more blocks, so we need to increase the size
23  // if needed.
24  block_effects_.SetSize(graph_->GetBlocks().size());
25  loop_effects_.SetSize(graph_->GetBlocks().size());
26
27  // In DEBUG mode, ensure side effects are properly initialized to empty.
28  if (kIsDebugBuild) {
29    for (HReversePostOrderIterator it(*graph_); !it.Done(); it.Advance()) {
30      HBasicBlock* block = it.Current();
31      SideEffects effects = GetBlockEffects(block);
32      DCHECK(effects.DoesNothing());
33      if (block->IsLoopHeader()) {
34        effects = GetLoopEffects(block);
35        DCHECK(effects.DoesNothing());
36      }
37    }
38  }
39
40  // Do a post order visit to ensure we visit a loop header after its loop body.
41  for (HPostOrderIterator it(*graph_); !it.Done(); it.Advance()) {
42    HBasicBlock* block = it.Current();
43
44    SideEffects effects = SideEffects::None();
45    // Update `effects` with the side effects of all instructions in this block.
46    for (HInstructionIterator inst_it(block->GetInstructions()); !inst_it.Done();
47         inst_it.Advance()) {
48      HInstruction* instruction = inst_it.Current();
49      effects = effects.Union(instruction->GetSideEffects());
50      // If all side effects are represented, scanning further will not add any
51      // more information to side-effects of this block.
52      if (effects.DoesAll()) {
53        break;
54      }
55    }
56
57    block_effects_.Put(block->GetBlockId(), effects);
58
59    if (block->IsLoopHeader()) {
60      // The side effects of the loop header are part of the loop.
61      UpdateLoopEffects(block->GetLoopInformation(), effects);
62      HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader();
63      if (pre_header->IsInLoop()) {
64        // Update the side effects of the outer loop with the side effects of the inner loop.
65        // Note that this works because we know all the blocks of the inner loop are visited
66        // before the loop header of the outer loop.
67        UpdateLoopEffects(pre_header->GetLoopInformation(), GetLoopEffects(block));
68      }
69    } else if (block->IsInLoop()) {
70      // Update the side effects of the loop with the side effects of this block.
71      UpdateLoopEffects(block->GetLoopInformation(), effects);
72    }
73  }
74  has_run_ = true;
75}
76
77SideEffects SideEffectsAnalysis::GetLoopEffects(HBasicBlock* block) const {
78  DCHECK(block->IsLoopHeader());
79  return loop_effects_.Get(block->GetBlockId());
80}
81
82SideEffects SideEffectsAnalysis::GetBlockEffects(HBasicBlock* block) const {
83  return block_effects_.Get(block->GetBlockId());
84}
85
86void SideEffectsAnalysis::UpdateLoopEffects(HLoopInformation* info, SideEffects effects) {
87  int id = info->GetHeader()->GetBlockId();
88  loop_effects_.Put(id, loop_effects_.Get(id).Union(effects));
89}
90
91}  // namespace art
92