[Bug tree-optimization/91940] __builtin_bswap16 loop optimization

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91940

--- Comment #7 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #1)
> The loop with the rotate is vectorized, while the one with __builtin_bswap16
> is not.

It is a bit surprising that we do not canonicalize one to the other somewhere
in the middle-end.