http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20020
--- Comment #10 from Gary Funck <gary at intrepid dot com> 2011-07-08 16:58:55 UTC --- Note: I don't know how this fix fits in with the x86_64 ABI, and obviously once this fix is in place, the binary call interface will change for 128 bit struct/union arguments. As noted in the previous reply, expand_call tried passing the argument (of TImode) in an XFmode (SSE) register. That may or may not be permitted by the call ABI.