yosys/tests/opt/opt_rmdff.ys

read_verilog -icells opt_rmdff.v
prep
design -stash gold

read_verilog -icells opt_rmdff.v
proc
opt_dff

select -assert-count 0 c:remove*
select -assert-min 7 c:keep*
select -assert-count 0  t:$dffe 7:$_DFFE_* %u c:noenable* %i

design -stash gate

design -import gold -as gold
design -import gate -as gate

cd gold
# fix up the "EN is don't care" cases, so that the gold output can't
# become defined by using the properties of an undefined enable. (Both
# remove6 and remove15 have active-low enables.)
connect -port remove6 EN 1'b1
connect -port remove15 E 1'b1
cd ..

clk2fflogic
opt_clean

miter -equiv -ignore_gold_x -make_assert -make_outputs -make_outcmp -flatten gold gate miter
hierarchy -top miter

sat -verify -prove-asserts -enable_undef -set-init-undef -seq 10 -show-public miter