https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88671
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- OK, so the question would be whether unsinged int __attribute__((vector_size(8))) is of type __m64 (I guess x87 psABI terms are not C language lawyer terms). But yes, even when naming the type __m64 clang doesn't pass in mmx regs.