read_verilog adffs.v
proc
async2sync # converts async flops to a 'sync' variant clocked by a 'super'-clock
flatten
equiv_opt -assert -map +/ice40/cells_sim.v synth_ice40 # equivalency check
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_DFFN
select -assert-count 2 t:SB_DFFSR
select -assert-count 7 t:SB_LUT4
select -assert-none t:SB_DFF t:SB_DFFN t:SB_DFFSR t:SB_LUT4 %% t:* %D