[Bug tree-optimization/114047] `(cast)(cast)a != a` for large unsigned _BitInt should be produce better code

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114047

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note there is a generic (non _BitInt) issue with __builtin_sub_overflow  vs the
other comparison too; on some targets using a bit mask is better while on
others using the `<=` test is better.