// Copyright 2015 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_INTERPRETER_BYTECODE_LABEL_H_
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#define V8_INTERPRETER_BYTECODE_LABEL_H_
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#include <algorithm>
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#include "src/zone/zone-containers.h"
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namespace v8 {
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namespace internal {
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namespace interpreter {
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class BytecodeArrayBuilder;
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// A label representing a branch target in a bytecode array. When a
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// label is bound, it represents a known position in the bytecode
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// array. For labels that are forward references there can be at most
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// one reference whilst it is unbound.
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class V8_EXPORT_PRIVATE BytecodeLabel final {
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public:
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BytecodeLabel() : bound_(false), offset_(kInvalidOffset) {}
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bool is_bound() const { return bound_; }
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size_t offset() const { return offset_; }
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private:
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static const size_t kInvalidOffset = static_cast<size_t>(-1);
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void bind_to(size_t offset) {
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DCHECK(!bound_ && offset != kInvalidOffset);
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offset_ = offset;
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bound_ = true;
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}
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void set_referrer(size_t offset) {
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DCHECK(!bound_ && offset != kInvalidOffset && offset_ == kInvalidOffset);
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offset_ = offset;
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}
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bool is_forward_target() const {
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return offset() != kInvalidOffset && !is_bound();
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}
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// There are three states for a label:
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// bound_ offset_
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// UNSET false kInvalidOffset
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// FORWARD_TARGET false Offset of referring jump
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// BACKWARD_TARGET true Offset of label in bytecode array when bound
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bool bound_;
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size_t offset_;
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friend class BytecodeArrayWriter;
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};
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// Class representing a branch target of multiple jumps.
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class V8_EXPORT_PRIVATE BytecodeLabels {
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public:
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explicit BytecodeLabels(Zone* zone) : labels_(zone) {}
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BytecodeLabel* New();
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void Bind(BytecodeArrayBuilder* builder);
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void BindToLabel(BytecodeArrayBuilder* builder, const BytecodeLabel& target);
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bool is_bound() const {
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bool is_bound = !labels_.empty() && labels_.front().is_bound();
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DCHECK(!is_bound ||
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std::all_of(labels_.begin(), labels_.end(),
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[](const BytecodeLabel& l) { return l.is_bound(); }));
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return is_bound;
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}
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bool empty() const { return labels_.empty(); }
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private:
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ZoneLinkedList<BytecodeLabel> labels_;
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DISALLOW_COPY_AND_ASSIGN(BytecodeLabels);
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};
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} // namespace interpreter
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} // namespace internal
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} // namespace v8
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#endif // V8_INTERPRETER_BYTECODE_LABEL_H_
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