else if (op instanceof OPT_AddressConstantOperand) return VM_TypeReference.Address;
  private VM_TypeReference getRefTypeOf(OPT_Operand op) {    if (VM.VerifyAssertions) VM._assert(!op.isDefinitelyNull());    // op must be a RegisterOperand or some ConstantOperand    if (op instanceof OPT_StringConstantOperand)      return VM_TypeReference.JavaLangString;     else if (op instanceof OPT_AddressConstantOperand)      return VM_TypeReference.Address;    else       return op.asRegister().type;  }