1 /*
2 * Copyright (C) 2015 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 "dex_cache_array_fixups_arm.h"
18
19 #include "base/arena_containers.h"
20 #include "utils/dex_cache_arrays_layout-inl.h"
21
22 namespace art {
23 namespace arm {
24
25 /**
26 * Finds instructions that need the dex cache arrays base as an input.
27 */
28 class DexCacheArrayFixupsVisitor : public HGraphVisitor {
29 public:
DexCacheArrayFixupsVisitor(HGraph * graph)30 explicit DexCacheArrayFixupsVisitor(HGraph* graph)
31 : HGraphVisitor(graph),
32 dex_cache_array_bases_(std::less<const DexFile*>(),
33 // Attribute memory use to code generator.
34 graph->GetArena()->Adapter(kArenaAllocCodeGenerator)) {}
35
MoveBasesIfNeeded()36 void MoveBasesIfNeeded() {
37 for (const auto& entry : dex_cache_array_bases_) {
38 // Bring the base closer to the first use (previously, it was in the
39 // entry block) and relieve some pressure on the register allocator
40 // while avoiding recalculation of the base in a loop.
41 HArmDexCacheArraysBase* base = entry.second;
42 base->MoveBeforeFirstUserAndOutOfLoops();
43 }
44 }
45
46 private:
VisitLoadString(HLoadString * load_string)47 void VisitLoadString(HLoadString* load_string) OVERRIDE {
48 // If this is a load with PC-relative access to the dex cache methods array,
49 // we need to add the dex cache arrays base as the special input.
50 if (load_string->GetLoadKind() == HLoadString::LoadKind::kDexCachePcRelative) {
51 // Initialize base for target dex file if needed.
52 const DexFile& dex_file = load_string->GetDexFile();
53 HArmDexCacheArraysBase* base = GetOrCreateDexCacheArrayBase(dex_file);
54 // Update the element offset in base.
55 DexCacheArraysLayout layout(kArmPointerSize, &dex_file);
56 base->UpdateElementOffset(layout.StringOffset(load_string->GetStringIndex()));
57 // Add the special argument base to the load.
58 load_string->AddSpecialInput(base);
59 }
60 }
61
VisitInvokeStaticOrDirect(HInvokeStaticOrDirect * invoke)62 void VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) OVERRIDE {
63 // If this is an invoke with PC-relative access to the dex cache methods array,
64 // we need to add the dex cache arrays base as the special input.
65 if (invoke->HasPcRelativeDexCache()) {
66 // Initialize base for target method dex file if needed.
67 MethodReference target_method = invoke->GetTargetMethod();
68 HArmDexCacheArraysBase* base = GetOrCreateDexCacheArrayBase(*target_method.dex_file);
69 // Update the element offset in base.
70 DexCacheArraysLayout layout(kArmPointerSize, target_method.dex_file);
71 base->UpdateElementOffset(layout.MethodOffset(target_method.dex_method_index));
72 // Add the special argument base to the method.
73 DCHECK(!invoke->HasCurrentMethodInput());
74 invoke->AddSpecialInput(base);
75 }
76 }
77
GetOrCreateDexCacheArrayBase(const DexFile & dex_file)78 HArmDexCacheArraysBase* GetOrCreateDexCacheArrayBase(const DexFile& dex_file) {
79 // Ensure we only initialize the pointer once for each dex file.
80 auto lb = dex_cache_array_bases_.lower_bound(&dex_file);
81 if (lb != dex_cache_array_bases_.end() &&
82 !dex_cache_array_bases_.key_comp()(&dex_file, lb->first)) {
83 return lb->second;
84 }
85
86 // Insert the base at the start of the entry block, move it to a better
87 // position later in MoveBaseIfNeeded().
88 HArmDexCacheArraysBase* base = new (GetGraph()->GetArena()) HArmDexCacheArraysBase(dex_file);
89 HBasicBlock* entry_block = GetGraph()->GetEntryBlock();
90 entry_block->InsertInstructionBefore(base, entry_block->GetFirstInstruction());
91 dex_cache_array_bases_.PutBefore(lb, &dex_file, base);
92 return base;
93 }
94
95 using DexCacheArraysBaseMap =
96 ArenaSafeMap<const DexFile*, HArmDexCacheArraysBase*, std::less<const DexFile*>>;
97 DexCacheArraysBaseMap dex_cache_array_bases_;
98 };
99
Run()100 void DexCacheArrayFixups::Run() {
101 if (graph_->HasIrreducibleLoops()) {
102 // Do not run this optimization, as irreducible loops do not work with an instruction
103 // that can be live-in at the irreducible loop header.
104 return;
105 }
106 DexCacheArrayFixupsVisitor visitor(graph_);
107 visitor.VisitInsertionOrder();
108 visitor.MoveBasesIfNeeded();
109 }
110
111 } // namespace arm
112 } // namespace art
113