https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71310
--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> --- This happens because of /* Find the smallest nice mode to use. */ for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode; mode = GET_MODE_WIDER_MODE (mode)) if (GET_MODE_BITSIZE (mode) >= bitsize) break; in stor-layout.c:finish_bitfield_representative .