[Bug tree-optimization/123330] Optimization fails with standard branchless idiom with power of 2s

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123330

--- Comment #3 from Tobias Schlüter <tobi at gcc dot gnu.org> ---
Ah, sorry for the second reply.  I'm aware of __builtin_clzg but it seems to
have only been added in 2013, which is too recent for my purposes,
unfortunately.