powerpc64 builtin_va_arg and variable size structures

[David Edelsohn]

>>>>> Alan Modra writes:

Alan> I can't see anything in the
Alan> PPC64 ABI that mandates special treatment for variable size
Alan> structures.  Can someone say why function_arg behaves this way?

	GCC parameter passing requires passing variable sized structures
by reference.  It cannot handle passing by value.  See the HP/PA port and
the discussion from last Fall.

David