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