def _compute_register_list(self, operand):
        """Return operand register list.
        """

        ret = []
        for reg_range in operand.reg_list:
            if len(reg_range) == 1:
                ret.append(ReilRegisterOperand(reg_range[0].name, reg_range[0].size))
            else:
                reg_num = int(reg_range[0].name[1:])    # Assuming the register is named with one letter + number
                reg_end = int(reg_range[1].name[1:])
                if reg_num > reg_end:
                    raise NotImplementedError("Instruction Not Implemented: Invalid register range.")
                while reg_num <= reg_end:
                    ret.append(ReilRegisterOperand(reg_range[0].name[0] + str(reg_num), reg_range[0].size))
                    reg_num = reg_num + 1

        return ret
Return operand register list.