https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89626
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Looks like the preprocess conditional identifier does not recognize __int128 as something it should be used with vector. I doubt this is a real bug as vector __int128 is not defined in the PowerPC specifications. vector unsigned __int128 is accepted by accident really, recongizing unsigned as something vector can come beforehand.
