https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70542
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Created attachment 38191 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38191&action=edit gcc6-pr70542.patch Perhaps better fix. Looking at PR64286, the comment is right, if we change somehow the definition for VECTOR_MODE_P, we need to make sure all uses are modified, or none. But there is tons of reasons why some of them could fail, e.g. for the copy_needed case there is lots of tests that can fail, but even for the !copy_needed case it could fail to get recognized etc., and we are unable to handle all the uses as a single transaction.