https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87691
--- Comment #3 from Jozef Lawrynowicz <jozef.l at mittosystems dot com> --- Perhaps it is sufficient to check targetm.pass_by_reference, i.e. if the struct/union with the given mode would be passed by reference, then it is ok to give the struct/union a mode outside the MODE_INT class.
