Macro fiat_bernstein_yang_invert 

macro_rules! fiat_bernstein_yang_invert {
    (
        a: $a:expr,
        one: $one:expr,
        d: $d:expr,
        nlimbs: $nlimbs:expr,
        word: $word:ty,
        non_mont: $non_mont_type: expr,
        mont: $mont_type: expr,
        from_mont: $from_mont:ident,
        mul: $mul:ident,
        neg: $neg:ident,
        divstep_precomp: $divstep_precomp:ident,
        divstep: $divstep:ident,
        msat: $msat:ident,
        selectnz: $selectznz:ident
    ) => { ... };
}

Emit wrapper function for a fiat-crypto generated implementation of the Bernstein-Yang (a.k.a. safegcd) modular inversion algorithm.