Function script_cut 

pub fn script_cut(
    top: &str,
    params: &[(&str, &str)],
    undefined: Undefined,
    units: &[&str],
) -> String

script_reading with every instance of the units modules cut out: each module read from units.v as its ports alone (read_verilog -lib, its body never elaborated; a module no unit is named is an error), and once the design is flat and written, each instance turned into ports of the top (expose -evert) — its outputs inputs named <instance>.<port>[bit], its inputs outputs of the same names.