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
19 namespace art {
20
Run()21 bool SideEffectsAnalysis::Run() {
22 // Inlining might have created more blocks, so we need to increase the size
23 // if needed.
24 block_effects_.resize(graph_->GetBlocks().size());
25 loop_effects_.resize(graph_->GetBlocks().size());
26
27 // In DEBUG mode, ensure side effects are properly initialized to empty.
28 if (kIsDebugBuild) {
29 for (HBasicBlock* block : graph_->GetReversePostOrder()) {
30 SideEffects effects = GetBlockEffects(block);
31 DCHECK(effects.DoesNothing());
32 if (block->IsLoopHeader()) {
33 effects = GetLoopEffects(block);
34 DCHECK(effects.DoesNothing());
35 }
36 }
37 }
38
39 // Do a post order visit to ensure we visit a loop header after its loop body.
40 for (HBasicBlock* block : graph_->GetPostOrder()) {
41 SideEffects effects = SideEffects::None();
42 // Update `effects` with the side effects of all instructions in this block.
43 for (HInstructionIterator inst_it(block->GetInstructions()); !inst_it.Done();
44 inst_it.Advance()) {
45 HInstruction* instruction = inst_it.Current();
46 effects = effects.Union(instruction->GetSideEffects());
47 // If all side effects are represented, scanning further will not add any
48 // more information to side-effects of this block.
49 if (effects.DoesAll()) {
50 break;
51 }
52 }
53
54 block_effects_[block->GetBlockId()] = effects;
55
56 if (block->IsLoopHeader()) {
57 // The side effects of the loop header are part of the loop.
58 UpdateLoopEffects(block->GetLoopInformation(), effects);
59 HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader();
60 if (pre_header->IsInLoop()) {
61 // Update the side effects of the outer loop with the side effects of the inner loop.
62 // Note that this works because we know all the blocks of the inner loop are visited
63 // before the loop header of the outer loop.
64 UpdateLoopEffects(pre_header->GetLoopInformation(), GetLoopEffects(block));
65 }
66 } else if (block->IsInLoop()) {
67 // Update the side effects of the loop with the side effects of this block.
68 UpdateLoopEffects(block->GetLoopInformation(), effects);
69 }
70 }
71 has_run_ = true;
72 return true;
73 }
74
GetLoopEffects(HBasicBlock * block) const75 SideEffects SideEffectsAnalysis::GetLoopEffects(HBasicBlock* block) const {
76 DCHECK(block->IsLoopHeader());
77 return loop_effects_[block->GetBlockId()];
78 }
79
GetBlockEffects(HBasicBlock * block) const80 SideEffects SideEffectsAnalysis::GetBlockEffects(HBasicBlock* block) const {
81 return block_effects_[block->GetBlockId()];
82 }
83
UpdateLoopEffects(HLoopInformation * info,SideEffects effects)84 void SideEffectsAnalysis::UpdateLoopEffects(HLoopInformation* info, SideEffects effects) {
85 uint32_t id = info->GetHeader()->GetBlockId();
86 loop_effects_[id] = loop_effects_[id].Union(effects);
87 }
88
89 } // namespace art
90