[Bug tree-optimization/86136] Modular multiplication optimization

[mcccs at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86136

--- Comment #3 from MCCCS <mcccs at gmx dot com> ---
What about

unsigned int k (unsigned int a) {
    if (a > 5) {
        __builtin_unreachable();
    }
    return (a * 83) % 5;
}