yosys/tests/ice40/adffs.ys

read_verilog adffs.v
proc
async2sync
synth -flatten -run coarse # technology-independent coarse grained synthesis
equiv_opt -assert -map +/ice40/cells_sim.v synth_ice40 # equivalency check same as technology-dependent fine-grained synthesis
design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
cd top # Constrain all select calls below inside the top module
select -assert-count 1 t:SB_DFF
select -assert-count 1 t:SB_DFFE
select -assert-count 4 t:SB_LUT4
#select -assert-none t:SB_LUT4 t:SB_DFFR t:SB_DFFE t:$_DFFSR_NPP_ t:$_DFFSR_PPP_ %% t:* %D
write_verilog adffs_synth.v