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      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 #ifndef ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
     18 #define ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
     19 
     20 #include "base/scoped_arena_allocator.h"
     21 #include "base/scoped_arena_containers.h"
     22 #include "nodes.h"
     23 #include "optimization.h"
     24 
     25 namespace art {
     26 
     27 /**
     28  * Transforms a graph into SSA form. The liveness guarantees of
     29  * this transformation are listed below. A DEX register
     30  * being killed means its value at a given position in the code
     31  * will not be available to its environment uses. A merge in the
     32  * following text is materialized as a `HPhi`.
     33  *
     34  * (a) Dex registers that do not require merging (that is, they do not
     35  *     have different values at a join block) are available to all their
     36  *     environment uses. Note that it does not imply the instruction will
     37  *     have a physical location after register allocation. See the
     38  *     SsaLivenessAnalysis phase.
     39  *
     40  * (b) Dex registers that require merging, and the merging gives
     41  *     incompatible types, will be killed for environment uses of that merge.
     42  *
     43  * (c) When the `debuggable` flag is passed to the compiler, Dex registers
     44  *     that require merging and have a proper type after the merge, are
     45  *     available to all their environment uses. If the `debuggable` flag
     46  *     is not set, values of Dex registers only used by environments
     47  *     are killed.
     48  */
     49 class SsaBuilder : public ValueObject {
     50  public:
     51   SsaBuilder(HGraph* graph,
     52              Handle<mirror::ClassLoader> class_loader,
     53              Handle<mirror::DexCache> dex_cache,
     54              VariableSizedHandleScope* handles,
     55              ScopedArenaAllocator* local_allocator)
     56       : graph_(graph),
     57         class_loader_(class_loader),
     58         dex_cache_(dex_cache),
     59         handles_(handles),
     60         agets_fixed_(false),
     61         local_allocator_(local_allocator),
     62         ambiguous_agets_(local_allocator->Adapter(kArenaAllocGraphBuilder)),
     63         ambiguous_asets_(local_allocator->Adapter(kArenaAllocGraphBuilder)),
     64         uninitialized_strings_(local_allocator->Adapter(kArenaAllocGraphBuilder)),
     65         uninitialized_string_phis_(local_allocator->Adapter(kArenaAllocGraphBuilder)) {
     66     graph_->InitializeInexactObjectRTI(handles);
     67   }
     68 
     69   GraphAnalysisResult BuildSsa();
     70 
     71   HInstruction* GetFloatOrDoubleEquivalent(HInstruction* instruction, DataType::Type type);
     72   HInstruction* GetReferenceTypeEquivalent(HInstruction* instruction);
     73 
     74   void MaybeAddAmbiguousArrayGet(HArrayGet* aget) {
     75     DataType::Type type = aget->GetType();
     76     DCHECK(!DataType::IsFloatingPointType(type));
     77     if (DataType::IsIntOrLongType(type)) {
     78       ambiguous_agets_.push_back(aget);
     79     }
     80   }
     81 
     82   void MaybeAddAmbiguousArraySet(HArraySet* aset) {
     83     DataType::Type type = aset->GetValue()->GetType();
     84     if (DataType::IsIntOrLongType(type)) {
     85       ambiguous_asets_.push_back(aset);
     86     }
     87   }
     88 
     89   void AddUninitializedString(HNewInstance* string) {
     90     // In some rare cases (b/27847265), the same NewInstance may be seen
     91     // multiple times. We should only consider it once for removal, so we
     92     // ensure it is not added more than once.
     93     // Note that we cannot check whether this really is a NewInstance of String
     94     // before RTP. We DCHECK that in RemoveRedundantUninitializedStrings.
     95     if (!ContainsElement(uninitialized_strings_, string)) {
     96       uninitialized_strings_.push_back(string);
     97     }
     98   }
     99 
    100   void AddUninitializedStringPhi(HInvoke* invoke) {
    101     uninitialized_string_phis_.push_back(invoke);
    102   }
    103 
    104  private:
    105   void SetLoopHeaderPhiInputs();
    106   void FixEnvironmentPhis();
    107   void FixNullConstantType();
    108   void EquivalentPhisCleanup();
    109   void RunPrimitiveTypePropagation();
    110 
    111   // Attempts to resolve types of aget(-wide) instructions and type values passed
    112   // to aput(-wide) instructions from reference type information on the array
    113   // input. Returns false if the type of an array is unknown.
    114   bool FixAmbiguousArrayOps();
    115 
    116   bool TypeInputsOfPhi(HPhi* phi, ScopedArenaVector<HPhi*>* worklist);
    117   bool UpdatePrimitiveType(HPhi* phi, ScopedArenaVector<HPhi*>* worklist);
    118   void ProcessPrimitiveTypePropagationWorklist(ScopedArenaVector<HPhi*>* worklist);
    119 
    120   HFloatConstant* GetFloatEquivalent(HIntConstant* constant);
    121   HDoubleConstant* GetDoubleEquivalent(HLongConstant* constant);
    122   HPhi* GetFloatDoubleOrReferenceEquivalentOfPhi(HPhi* phi, DataType::Type type);
    123   HArrayGet* GetFloatOrDoubleEquivalentOfArrayGet(HArrayGet* aget);
    124 
    125   void RemoveRedundantUninitializedStrings();
    126   bool ReplaceUninitializedStringPhis();
    127   bool HasAliasInEnvironments(HInstruction* instruction);
    128 
    129   HGraph* const graph_;
    130   Handle<mirror::ClassLoader> class_loader_;
    131   Handle<mirror::DexCache> dex_cache_;
    132   VariableSizedHandleScope* const handles_;
    133 
    134   // True if types of ambiguous ArrayGets have been resolved.
    135   bool agets_fixed_;
    136 
    137   ScopedArenaAllocator* const local_allocator_;
    138   ScopedArenaVector<HArrayGet*> ambiguous_agets_;
    139   ScopedArenaVector<HArraySet*> ambiguous_asets_;
    140   ScopedArenaVector<HNewInstance*> uninitialized_strings_;
    141   ScopedArenaVector<HInvoke*> uninitialized_string_phis_;
    142 
    143   DISALLOW_COPY_AND_ASSIGN(SsaBuilder);
    144 };
    145 
    146 }  // namespace art
    147 
    148 #endif  // ART_COMPILER_OPTIMIZING_SSA_BUILDER_H_
    149