opt - perform simple optimizations

yosys> help opt

opt [options] [selection]

This pass calls all the other opt_* passes in a useful order. This performs
a series of trivial optimizations and cleanups. This pass executes the other
passes in the following order:

    opt_expr [-mux_undef] [-mux_bool] [-undriven] [-noclkinv] [-fine] [-full] [-keepdc]
    opt_merge [-share_all] -nomux

    do
        opt_muxtree
        opt_reduce [-fine] [-full]
        opt_merge [-share_all]
        opt_share  (-full only)
        opt_dff [-nodffe] [-nosdff] [-keepdc] [-sat]  (except when called with -noff)
        opt_clean [-purge]
        opt_expr [-mux_undef] [-mux_bool] [-undriven] [-noclkinv] [-fine] [-full] [-keepdc]
    while <changed design>

When called with -fast the following script is used instead:

    do
        opt_expr [-mux_undef] [-mux_bool] [-undriven] [-noclkinv] [-fine] [-full] [-keepdc]
        opt_merge [-share_all]
        opt_dff [-nodffe] [-nosdff] [-keepdc] [-sat]  (except when called with -noff)
        opt_clean [-purge]
    while <changed design in opt_dff>

Note: Options in square brackets (such as [-keepdc]) are passed through to
the opt_* commands when given to 'opt'.