https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83964
--- Comment #19 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The main issue of the builtins that have been reverted was that it was too tied to a particular HW instruction, if the hw instruction doesn't exist, don't support it (and this wasn't working properly, it was supported in some cases where it just ICEd). Better is to come up with a generic builtin that does something, and then targets can optimize if they can and there is some fallback that can handle it when there is nothing better available.
