[Bug tree-optimization/90838] Detect table-based ctz implementation

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90838

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
It is generally a win for cases where the condition can't be predicted, while
if it can, jumps are much better.  We have dozens or hundreds of PRs about this
in either direction on x86.