https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118795
--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> --- typedef unsigned char V __attribute__((vector_size (16))); V foo (V x) { return __builtin_shuffle (x, x, (V) { 0, 0, 0, 0, 4, 4, 4, 4, 8, 8, 8, 8, 12, 12, 12, 12 }); } compiles fine.