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      1 /*
      2  * Copyright (C) 2016 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_BLOCK_BUILDER_H_
     18 #define ART_COMPILER_OPTIMIZING_BLOCK_BUILDER_H_
     19 
     20 #include "base/arena_containers.h"
     21 #include "base/arena_object.h"
     22 #include "dex_file.h"
     23 #include "nodes.h"
     24 
     25 namespace art {
     26 
     27 class HBasicBlockBuilder : public ValueObject {
     28  public:
     29   HBasicBlockBuilder(HGraph* graph,
     30                      const DexFile* const dex_file,
     31                      const DexFile::CodeItem& code_item)
     32       : arena_(graph->GetArena()),
     33         graph_(graph),
     34         dex_file_(dex_file),
     35         code_item_(code_item),
     36         branch_targets_(code_item.insns_size_in_code_units_,
     37                         nullptr,
     38                         arena_->Adapter(kArenaAllocGraphBuilder)),
     39         throwing_blocks_(kDefaultNumberOfThrowingBlocks, arena_->Adapter(kArenaAllocGraphBuilder)),
     40         number_of_branches_(0u) {}
     41 
     42   // Creates basic blocks in `graph_` at branch target dex_pc positions of the
     43   // `code_item_`. Blocks are connected but left unpopulated with instructions.
     44   // TryBoundary blocks are inserted at positions where control-flow enters/
     45   // exits a try block.
     46   bool Build();
     47 
     48   size_t GetNumberOfBranches() const { return number_of_branches_; }
     49   HBasicBlock* GetBlockAt(uint32_t dex_pc) const { return branch_targets_[dex_pc]; }
     50 
     51  private:
     52   // Creates a basic block starting at given `dex_pc`.
     53   HBasicBlock* MaybeCreateBlockAt(uint32_t dex_pc);
     54 
     55   // Creates a basic block for bytecode instructions at `semantic_dex_pc` and
     56   // stores it under the `store_dex_pc` key. This is used when multiple blocks
     57   // share the same semantic dex_pc, e.g. when building switch decision trees.
     58   HBasicBlock* MaybeCreateBlockAt(uint32_t semantic_dex_pc, uint32_t store_dex_pc);
     59 
     60   bool CreateBranchTargets();
     61   void ConnectBasicBlocks();
     62   void InsertTryBoundaryBlocks();
     63 
     64   // Helper method which decides whether `catch_block` may have live normal
     65   // predecessors and thus whether a synthetic catch block needs to be created
     66   // to avoid mixing normal and exceptional predecessors.
     67   // Should only be called during InsertTryBoundaryBlocks on blocks at catch
     68   // handler dex_pcs.
     69   bool MightHaveLiveNormalPredecessors(HBasicBlock* catch_block);
     70 
     71   ArenaAllocator* const arena_;
     72   HGraph* const graph_;
     73 
     74   const DexFile* const dex_file_;
     75   const DexFile::CodeItem& code_item_;
     76 
     77   ArenaVector<HBasicBlock*> branch_targets_;
     78   ArenaVector<HBasicBlock*> throwing_blocks_;
     79   size_t number_of_branches_;
     80 
     81   static constexpr size_t kDefaultNumberOfThrowingBlocks = 2u;
     82 
     83   DISALLOW_COPY_AND_ASSIGN(HBasicBlockBuilder);
     84 };
     85 
     86 }  // namespace art
     87 
     88 #endif  // ART_COMPILER_OPTIMIZING_BLOCK_BUILDER_H_
     89