http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59615
--- Comment #5 from H. Peter Anvin <hpa at zytor dot com> --- Please don't get hung up on the specific example; I just picked one that was small and self-contained. The biggest reason we can't use gcc's native bits in the kernel are items where we have to use the kernel's "alternative" feature, where the code is dynamically patched.