mmix ICEs on mainline during building of libc

[Hans-Peter Nilsson]

On Sat, 1 Mar 2003, Andreas Jaeger wrote:
> Bootstrapping mmix in a ueberbaum fails in string/wcsspn.c:

>From the locus of the failure, it looks as if this change:
2003-02-28  Dale Johannesen <dalej@apple.com>

        * loop.c (struct movable): Add insert_temp, shrink savemode.
	(scan_loop): Accept invariants that require copying; mark as
        insert_temp.
	(combine_movables): Don't combine insert_temp movables.
	(move_movables): Insert copies for insert_temp movables.
	Don't record the info based on regno for insert_temp's.

uncovered the need for moves between CCmodeish operands.
I see other ports have such patterns, so I'll add one to mmix.md.

Strange that it hasn't been needed until now.

brgds, H-P