[Interpreter] Move jump processing to bytecode array writer.

src/interpreter/bytecode-label.h

+// 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_INTERPRETER_BYTECODE_LABEL_H_
+#define V8_INTERPRETER_BYTECODE_LABEL_H_
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+
+// A label representing a branch target in a bytecode array. When a
+// label is bound, it represents a known position in the bytecode
+// array. For labels that are forward references there can be at most
+// one reference whilst it is unbound.
+class BytecodeLabel final {
+ public:
+  BytecodeLabel() : bound_(false), offset_(kInvalidOffset) {}
+
+  bool is_bound() const { return bound_; }
+  size_t offset() const { return offset_; }
+
+ private:
+  static const size_t kInvalidOffset = static_cast<size_t>(-1);
+
+  void bind_to(size_t offset) {
+    DCHECK(!bound_ && offset != kInvalidOffset);
+    offset_ = offset;
+    bound_ = true;
+  }
+
+  void set_referrer(size_t offset) {
+    DCHECK(!bound_ && offset != kInvalidOffset && offset_ == kInvalidOffset);
+    offset_ = offset;
+  }
+
+  bool is_forward_target() const {
+    return offset() != kInvalidOffset && !is_bound();
+  }
+
+  // There are three states for a label:
+  //                    bound_   offset_
+  //  UNSET             false    kInvalidOffset
+  //  FORWARD_TARGET    false    Offset of referring jump
+  //  BACKWARD_TARGET    true    Offset of label in bytecode array when bound
+  bool bound_;
+  size_t offset_;
+
+  friend class BytecodeArrayWriter;
+};
+
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_INTERPRETER_BYTECODE_LABEL_H_