As far as I know these should be freely reassociatable just like
the floating point MAXC/MINC instructions.
The test changes demonstrate that something happened from this
patch, but I'm not sure we always made the right choice. I
think the fact that llc defaults to "generic" CPU is causing
us to not have a scheduler model so MachineCombiner doesn't
make the best decisions. But this isn't unique to these
instructions.