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_ 80
