https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77359
--- Comment #4 from David Edelsohn <dje at gcc dot gnu.org> --- Altivec works on AIX, which requires 128 bit alignment. So GCC and AIX are able to cooperate to generate the necessary alignment. The stack pointer is supposed to maintain quadword alignment on AIX. Presumably something in the rs6000 backend is not maintaining or not instructing the common part of GCC to maintain the alignment on AIX, but presumably is maintained on Linux.
