https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105640
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- It isn't implemented on anything but x86, nvptx and gcn. https://gcc.gnu.org/legacy-ml/gcc-patches/2019-10/threads.html#02066 has some more details. aarch64 would be another HPC related target.
