[Bug tree-optimization/124675] Missed optimization: Fold `(x % C) + (x % C < 0 ? C : 0)` to `x & (C-1)` when C is a power of 2

[Explorer09 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124675

--- Comment #2 from Kang-Che Sung <Explorer09 at gmail dot com> ---
I move the division part of the issue (in contrast with the modulo part) into a
separate report: bug 124680.