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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         quicken_index_for_dex_pc_(std::less<uint32_t>(), arena_->Adapter()) {}
     42 
     43   // Creates basic blocks in `graph_` at branch target dex_pc positions of the
     44   // `code_item_`. Blocks are connected but left unpopulated with instructions.
     45   // TryBoundary blocks are inserted at positions where control-flow enters/
     46   // exits a try block.
     47   bool Build();
     48 
     49   size_t GetNumberOfBranches() const { return number_of_branches_; }
     50   HBasicBlock* GetBlockAt(uint32_t dex_pc) const { return branch_targets_[dex_pc]; }
     51 
     52   size_t GetQuickenIndex(uint32_t dex_pc) const;
     53 
     54  private:
     55   // Creates a basic block starting at given `dex_pc`.
     56   HBasicBlock* MaybeCreateBlockAt(uint32_t dex_pc);
     57 
     58   // Creates a basic block for bytecode instructions at `semantic_dex_pc` and
     59   // stores it under the `store_dex_pc` key. This is used when multiple blocks
     60   // share the same semantic dex_pc, e.g. when building switch decision trees.
     61   HBasicBlock* MaybeCreateBlockAt(uint32_t semantic_dex_pc, uint32_t store_dex_pc);
     62 
     63   bool CreateBranchTargets();
     64   void ConnectBasicBlocks();
     65   void InsertTryBoundaryBlocks();
     66 
     67   // Helper method which decides whether `catch_block` may have live normal
     68   // predecessors and thus whether a synthetic catch block needs to be created
     69   // to avoid mixing normal and exceptional predecessors.
     70   // Should only be called during InsertTryBoundaryBlocks on blocks at catch
     71   // handler dex_pcs.
     72   bool MightHaveLiveNormalPredecessors(HBasicBlock* catch_block);
     73 
     74   ArenaAllocator* const arena_;
     75   HGraph* const graph_;
     76 
     77   const DexFile* const dex_file_;
     78   const DexFile::CodeItem& code_item_;
     79 
     80   ArenaVector<HBasicBlock*> branch_targets_;
     81   ArenaVector<HBasicBlock*> throwing_blocks_;
     82   size_t number_of_branches_;
     83 
     84   // A table to quickly find the quicken index for the first instruction of a basic block.
     85   ArenaSafeMap<uint32_t, uint32_t> quicken_index_for_dex_pc_;
     86 
     87   static constexpr size_t kDefaultNumberOfThrowingBlocks = 2u;
     88 
     89   DISALLOW_COPY_AND_ASSIGN(HBasicBlockBuilder);
     90 };
     91 
     92 }  // namespace art
     93 
     94 #endif  // ART_COMPILER_OPTIMIZING_BLOCK_BUILDER_H_
     95