I'm pretty confident that --with-cpu=ultrasparc won't do any harm in
64-bit mode, but Jose (CC'ed as gcc upstream) will hopefully correct
me here if I'm wrong.
The cpu selected in --with-cpu impacts both -m64 and -m32 in a biarch
compiler. However, I can't say anything about the patch since I lack
the most basic context here, i.e. I have no idea what the contents of
that rules2 file are.