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 void 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 (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_[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
GetLoopEffects(HBasicBlock * block) const77 SideEffects SideEffectsAnalysis::GetLoopEffects(HBasicBlock* block) const {
78 DCHECK(block->IsLoopHeader());
79 return loop_effects_[block->GetBlockId()];
80 }
81
GetBlockEffects(HBasicBlock * block) const82 SideEffects SideEffectsAnalysis::GetBlockEffects(HBasicBlock* block) const {
83 return block_effects_[block->GetBlockId()];
84 }
85
UpdateLoopEffects(HLoopInformation * info,SideEffects effects)86 void SideEffectsAnalysis::UpdateLoopEffects(HLoopInformation* info, SideEffects effects) {
87 uint32_t id = info->GetHeader()->GetBlockId();
88 loop_effects_[id] = loop_effects_[id].Union(effects);
89 }
90
91 } // namespace art
92