https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97360
--- Comment #24 from Peter Bergner <bergner at gcc dot gnu.org> --- (In reply to Richard Biener from comment #22) > tree oi_uns_type = make_unsigned_type (256); > - vector_pair_type_node = build_distinct_type_copy (oi_uns_type); > SET_TYPE_MODE (vector_pair_type_node, POImode); So this doesn't work. Without that line vector_pair_type_node is NULL and the SET_TYPE_MODE() usage on the next line ends up dereferencing it and we SEGV.