https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67714
--- Comment #10 from ktkachov at gcc dot gnu.org --- Hi Nick, For this failure (among others) I proposed the series at: https://gcc.gnu.org/ml/gcc-patches/2016-01/msg01713.html that changes the PROMOTE_MODE implementation on arm to be consistent with the TARGET_PROMOTE_FUNCTION_MODE implementation i.e. to not do unsigned promotion of short types