[Bug tree-optimization/119420] `a >> 1 == 0` should be trasformed into `((unsigned)a) <= 1`

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119420

--- Comment #2 from Jeffrey A. Law <law at gcc dot gnu.org> ---
I'd marked this at some point for investigation on risc-v.  I think one of the
recent changes squashed all these into something sensible:

        sltiu   a0,a0,2 # 12    [c=8 l=4]  *riscv.md:3766
        ret             # 25    [c=0 l=4]  simple_return