https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89123
--- Comment #8 from Ian Lance Taylor <ian at airs dot com> --- Created attachment 45590 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45590&action=edit Sketch of patch Thanks. That does make the problem obvious. I've attached a sketch of what a patch should look like. Basically, we want to call instructions like stfle and km. As far as I can tell these are not available as GCC intrinsics, and as such will have to be invoked using __asm__. I'm not sure quite what that would look like on S/390. Hopefully this patch sketch will let you make some forward progress. Let me know if I can help.