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| 1 // Copyright 2015 the V8 project authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_ |
| 6 #define V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_ |
| 7 |
| 8 #include "src/bit-vector.h" |
| 9 #include "src/handles.h" |
| 10 #include "src/zone-containers.h" |
| 11 |
| 12 namespace v8 { |
| 13 namespace internal { |
| 14 |
| 15 class BytecodeArray; |
| 16 |
| 17 namespace compiler { |
| 18 |
| 19 class BytecodeBranchInfo; |
| 20 |
| 21 // A class for identifying the branch targets and their branch sites |
| 22 // within a bytecode array and also identifying which bytecodes are |
| 23 // reachable. This information can be used to construct the local |
| 24 // control flow logic for high-level IR graphs built from bytecode. |
| 25 // |
| 26 // NB This class relies on the only backwards branches in bytecode |
| 27 // being jumps back to loop headers. |
| 28 class BytecodeBranchAnalysis BASE_EMBEDDED { |
| 29 public: |
| 30 BytecodeBranchAnalysis(Handle<BytecodeArray> bytecode_array, Zone* zone); |
| 31 |
| 32 // Analyze the bytecodes to find the branch sites and their |
| 33 // targets. No other methods in this class return valid information |
| 34 // until this has been called. |
| 35 void Analyze(); |
| 36 |
| 37 // Offsets of bytecodes having a backward branch to the bytecode at |offset|. |
| 38 const ZoneVector<int>* BackwardBranchesTargetting(int offset) const; |
| 39 |
| 40 // Offsets of bytecodes having a forward branch to the bytecode at |offset|. |
| 41 const ZoneVector<int>* ForwardBranchesTargetting(int offset) const; |
| 42 |
| 43 // Returns true if the bytecode at |offset| is reachable. |
| 44 bool is_reachable(int offset) const { return reachable_.Contains(offset); } |
| 45 |
| 46 // Returns true if there are any forward branches to the bytecode at |
| 47 // |offset|. |
| 48 bool forward_branches_target(int offset) const { |
| 49 const ZoneVector<int>* sites = ForwardBranchesTargetting(offset); |
| 50 return sites != nullptr && sites->size() > 0; |
| 51 } |
| 52 |
| 53 // Returns true if there are any backward branches to the bytecode |
| 54 // at |offset|. |
| 55 bool backward_branches_target(int offset) const { |
| 56 const ZoneVector<int>* sites = BackwardBranchesTargetting(offset); |
| 57 return sites != nullptr && sites->size() > 0; |
| 58 } |
| 59 |
| 60 private: |
| 61 void AddBranch(int origin_offset, int target_offset); |
| 62 |
| 63 Zone* zone() const { return zone_; } |
| 64 Handle<BytecodeArray> bytecode_array() const { return bytecode_array_; } |
| 65 |
| 66 ZoneMap<int, BytecodeBranchInfo*> branch_infos_; |
| 67 Handle<BytecodeArray> bytecode_array_; |
| 68 BitVector reachable_; |
| 69 Zone* zone_; |
| 70 |
| 71 DISALLOW_COPY_AND_ASSIGN(BytecodeBranchAnalysis); |
| 72 }; |
| 73 |
| 74 |
| 75 } // namespace compiler |
| 76 } // namespace internal |
| 77 } // namespace v8 |
| 78 |
| 79 #endif // V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_ |
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