read_verilog tribuf.v
hierarchy -top tristate
proc
tribuf
flatten
synth
equiv_opt -assert -map +/xilinx/cells_sim.v -map +/simcells.v synth_xilinx # equivalency check
design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
cd tristate # Constrain all select calls below inside the top module
# TODO :: Tristate logic not yet supported; see https://github.com/YosysHQ/yosys/issues/1225
select -assert-count 1 t:$_TBUF_
select -assert-none t:$_TBUF_ %% t:* %D