[Interpreter] Enable assignments in expressions.

src/interpreter/bytecode-array-builder.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_ARRAY_BUILDER_H_
 #define V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 
 #include <vector>
 
 #include "src/ast.h"
@@ skipping 79 matching lines @@
   // Load the object at |slot_index| in |context| into the accumulator.
   BytecodeArrayBuilder& LoadContextSlot(Register context, int slot_index);
 
   // Stores the object in the accumulator into |slot_index| of |context|.
   BytecodeArrayBuilder& StoreContextSlot(Register context, int slot_index);
 
   // Register-accumulator transfers.
   BytecodeArrayBuilder& LoadAccumulatorWithRegister(Register reg);
   BytecodeArrayBuilder& StoreAccumulatorInRegister(Register reg);
 
+  // Register-register transfer.
+  BytecodeArrayBuilder& MoveRegister(Register from, Register to);
+
   // Named load property.
   BytecodeArrayBuilder& LoadNamedProperty(Register object, size_t name_index,
                                           int feedback_slot,
                                           LanguageMode language_mode);
   // Keyed load property. The key should be in the accumulator.
   BytecodeArrayBuilder& LoadKeyedProperty(Register object, int feedback_slot,
                                           LanguageMode language_mode);
 
   // Store properties. The value to be stored should be in the accumulator.
   BytecodeArrayBuilder& StoreNamedProperty(Register object, size_t name_index,
@@ skipping 240 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(TemporaryRegisterScope);
 };
 
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_