[interpreter] Use VisitForTest for loop conditions

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_
 
 #include "src/zone-containers.h"
 
 namespace v8 {
@@ skipping 44 matching lines @@
 
 // Class representing a branch target of multiple jumps.
 class BytecodeLabels {
  public:
   explicit BytecodeLabels(Zone* zone) : labels_(zone) {}
 
   BytecodeLabel* New();
 
   void Bind(BytecodeArrayBuilder* builder);
 
+  void BindToLabel(BytecodeArrayBuilder* builder, const BytecodeLabel& target);
+
+  bool is_bound() const {
+    bool is_bound = !labels_.empty() && labels_.at(0).is_bound();
+    DCHECK(!is_bound ||
+           std::all_of(labels_.begin(), labels_.end(),
+                       [](const BytecodeLabel& l) { return l.is_bound(); }));
+    return is_bound;
+  }
+
+  bool empty() const { return labels_.empty(); }
+
  private:
   ZoneVector<BytecodeLabel> labels_;
 
   DISALLOW_COPY_AND_ASSIGN(BytecodeLabels);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_LABEL_H_