https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70973
--- Comment #1 from dhowells at redhat dot com <dhowells at redhat dot com> --- There may be space that can be used in the memorder parameter: "The memory order parameter is a signed int, but only the lower 16 bits are reserved for the memory order. The remainder of the signed int is reserved for target use and should be 0. Use of the predefined atomic values ensures proper usage."
