setundef - replace undef values with defined constants

yosys> help setundef
setundef [options] [selection]
This command replaces undef (x) constants with defined (0/1) constants.
also set undriven nets to constant values
also expose undriven nets as inputs (use with -undriven)
replace with bits cleared (0)
replace with bits set (1)
replace with undef (x) bits, may be used with -undriven
replace with $anyseq drivers (for formal)
replace with $anyconst drivers (for formal)
-random <seed>
replace with random bits using the specified integer as seed
value for the random number generator.
also create/update init values for flip-flops
replace undef in cell parameters