https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71733
--- Comment #4 from Peter Bergner <bergner at gcc dot gnu.org> --- Aaron, the following patch seems to fix the problem for me. Can you give this a try? I'm currently bootstraapping and regtesting it. Index: gcc/config/rs6000/rs6000.c =================================================================== --- gcc/config/rs6000/rs6000.c (revision 237929) +++ gcc/config/rs6000/rs6000.c (working copy) @@ -4303,7 +4303,8 @@ rs6000_option_override_internal (bool gl { if (rs6000_isa_flags_explicit & OPTION_MASK_P8_VECTOR) error ("-mpower9-vector requires -mpower8-vector"); - rs6000_isa_flags &= ~OPTION_MASK_P9_VECTOR; + rs6000_isa_flags &= ~(OPTION_MASK_P9_VECTOR + | OPTION_MASK_P9_DFORM_VECTOR); } /* There have been bugs with -mvsx-timode that don't show up with -mlra,