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:
HBasicBlockBuilder(HGraph * graph,const DexFile * const dex_file,const DexFile::CodeItem & code_item)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 
GetNumberOfBranches()48   size_t GetNumberOfBranches() const { return number_of_branches_; }
GetBlockAt(uint32_t dex_pc)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