https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114566
--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Ah, vect_analyze_data_refs_alignment -> vect_compute_data_ref_alignment actually checks for this case 1136 if (max_alignment < vect_align_c 1137 || !vect_can_force_dr_alignment_p (base, 1138 vect_align_c * BITS_PER_UNIT)) and vect_can_force_dr_alignment_p returns true that the base (aka VAR_DECL a) can be forced to have dr alignment. But then nothing actually increases the alignment of the VAR_DECL. For vect_can_force_dr_alignment_p static VAR_DECLs there is the increase_alignment IPA pass (though just for -fsection-anchors?), and for automatic vars there is ensure_base_align, but for some reason that doesn't trigger.
