opt_lut - optimize LUT cells

    opt_lut [options] [selection]

This pass combines cascaded $lut cells with unused inputs.

    -dlogic <type>:<cell-port>=<LUT-input>[:<cell-port>=<LUT-input>...]
        preserve connections to dedicated logic cell <type> that has ports
        <cell-port> connected to LUT inputs <LUT-input>. this includes
        the case where both LUT and dedicated logic input are connected to
        the same constant.

    -limit N
        only perform the first N combines, then stop. useful for debugging.