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      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:
     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 
     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:
     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 
     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 
     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 
    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