https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70963
--- Comment #3 from Bill Schmidt <wschmidt at gcc dot gnu.org> --- Note also that your asm constraints are wrong. You need VSX registers, not Altivec registers, so you should be using the "wa" constraint instead of the "v" constraint. This is why you get some apparently wrong register numbers with your asm results.