https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113018
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- OK, so we're running into /* When a BB reduction doesn't have an even number of lanes strip it down, treating the remaining lane as scalar. ??? Selecting the optimal set of lanes to vectorize would be nice but SLP build for all lanes will fail quickly because we think we're going to need unrolling. */ if (kind == slp_inst_kind_bb_reduc && (scalar_stmts.length () & 1)) remain.safe_insert (0, gimple_get_lhs (scalar_stmts.pop ()->stmt)); pushing the "LHS" of an asm. __asm__("" : "=w" s_10 : "0" _1);