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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 
     11 namespace v8 {
     12 namespace internal {
     13 
     14 class BytecodeArray;
     15 
     16 namespace compiler {
     17 
     18 // A class for identifying branch targets within a bytecode array.
     19 // This information can be used to construct the local control flow
     20 // logic for high-level IR graphs built from bytecode.
     21 //
     22 // N.B. If this class is used to determine loop headers, then such a
     23 // usage relies on the only backwards branches in bytecode being jumps
     24 // back to loop headers.
     25 class BytecodeBranchAnalysis BASE_EMBEDDED {
     26  public:
     27   BytecodeBranchAnalysis(Handle<BytecodeArray> bytecode_array, Zone* zone);
     28 
     29   // Analyze the bytecodes to find the branch sites and their
     30   // targets. No other methods in this class return valid information
     31   // until this has been called.
     32   void Analyze();
     33 
     34   // Returns true if there are any forward branches to the bytecode at
     35   // |offset|.
     36   bool forward_branches_target(int offset) const {
     37     return is_forward_target_.Contains(offset);
     38   }
     39 
     40   // Returns true if there are any backward branches to the bytecode
     41   // at |offset|.
     42   bool backward_branches_target(int offset) const {
     43     return is_backward_target_.Contains(offset);
     44   }
     45 
     46  private:
     47   void AddBranch(int origin_offset, int target_offset);
     48 
     49   Zone* zone() const { return zone_; }
     50   Handle<BytecodeArray> bytecode_array() const { return bytecode_array_; }
     51 
     52   Handle<BytecodeArray> bytecode_array_;
     53   BitVector is_backward_target_;
     54   BitVector is_forward_target_;
     55   Zone* zone_;
     56 
     57   DISALLOW_COPY_AND_ASSIGN(BytecodeBranchAnalysis);
     58 };
     59 
     60 
     61 }  // namespace compiler
     62 }  // namespace internal
     63 }  // namespace v8
     64 
     65 #endif  // V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_
     66