Under -Os, gcc likes to inline memcpy into rep movsb (x86-64).
How can I make it actually call memcpy while keeping the -Os compiler option?

Is there anything more local than -fno-builtin-memcpy that makes it do that?
I would prefer something I could do from inside a C file which generates a direct call (calling it through a volatile pointer works does not generate a direct call).

https://godbolt.org/z/EjYbPaGzf