Extract FSM Does Not Work

[myzinsky]

Following the example here:

https://stackoverflow.com/questions/32645965/fsm-export-using-yosys/65638821#65638821

yosys -p 'read_verilog fsm.v; proc; opt; fsm -nomap; fsm_export -o test.kiss2'

does not export any kiss2 file :-(

Is that a bug? Or has the usage changed?

[Ravenslofty]

This could be #2402; if there are no FSMs detected, then fsm_export does nothing.

[MJChku]

Another answer is don't run opt; Just run proc; fsm ...

[nakengelhardt]

fsm_detect expects the following passes to be run beforehand: hierarchy -top <top>; proc; bmuxmap; opt -nodffe -nosdff

This is because fsm_detect works on a limited subset of FF cells, and also doesn't handle $bmux cells. These passes give the FSM detection heuristic the shape of design it expects.