https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79469
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |WONTFIX Status|NEW |RESOLVED --- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- So even though clang/LLVM has not implement the attribute yet (https://github.com/llvm/llvm-project/pull/81014), adding another extension is not a good idea for GCC so closing as won't fix. There is a reason why this got standarized is so it can be implemented in a cross compiler way. Also the builtin has an odd definition when it comes to the whole no side effects (though the attribute has that, it is not directly part of the a function call).