dffunmap - unmap clock enable and synchronous reset from FFs

yosys> help dffunmap

dffunmap [options] [selection]

This pass transforms FF types with clock enable and/or synchronous reset into
their base type (with neither clock enable nor sync reset) by emulating the
clock enable and synchronous reset with multiplexers on the cell input.

-ce-only

unmap only clock enables, leave synchronous resets alone.

-srst-only

unmap only synchronous resets, leave clock enables alone.