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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_
#define V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_
#include "src/bit-vector.h"
#include "src/handles.h"
#include "src/zone-containers.h"
namespace v8 {
namespace internal {
class BytecodeArray;
namespace compiler {
class BytecodeBranchInfo;
// A class for identifying the branch targets and their branch sites
// within a bytecode array and also identifying which bytecodes are
// reachable. This information can be used to construct the local
// control flow logic for high-level IR graphs built from bytecode.
//
// NB This class relies on the only backwards branches in bytecode
// being jumps back to loop headers.
class BytecodeBranchAnalysis BASE_EMBEDDED {
public:
BytecodeBranchAnalysis(Handle<BytecodeArray> bytecode_array, Zone* zone);
// Analyze the bytecodes to find the branch sites and their
// targets. No other methods in this class return valid information
// until this has been called.
void Analyze();
// Offsets of bytecodes having a backward branch to the bytecode at |offset|.
const ZoneVector<int>* BackwardBranchesTargetting(int offset) const;
// Offsets of bytecodes having a forward branch to the bytecode at |offset|.
const ZoneVector<int>* ForwardBranchesTargetting(int offset) const;
// Returns true if the bytecode at |offset| is reachable.
bool is_reachable(int offset) const { return reachable_.Contains(offset); }
// Returns true if there are any forward branches to the bytecode at
// |offset|.
bool forward_branches_target(int offset) const {
const ZoneVector<int>* sites = ForwardBranchesTargetting(offset);
return sites != nullptr && sites->size() > 0;
}
// Returns true if there are any backward branches to the bytecode
// at |offset|.
bool backward_branches_target(int offset) const {
const ZoneVector<int>* sites = BackwardBranchesTargetting(offset);
return sites != nullptr && sites->size() > 0;
}
private:
void AddBranch(int origin_offset, int target_offset);
Zone* zone() const { return zone_; }
Handle<BytecodeArray> bytecode_array() const { return bytecode_array_; }
ZoneMap<int, BytecodeBranchInfo*> branch_infos_;
Handle<BytecodeArray> bytecode_array_;
BitVector reachable_;
Zone* zone_;
DISALLOW_COPY_AND_ASSIGN(BytecodeBranchAnalysis);
};
} // namespace compiler
} // namespace internal
} // namespace v8
#endif // V8_COMPILER_BYTECODE_BRANCH_ANALYSIS_H_
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