Bug in reload_cse_move2add()

[Joern Rennecke]

> Good idea!  But what if the earliest register itself is incremented?
> (I haven't studied your patch yet)

In that case, the optimization would be disabled - because the luid is
incremented.  But I think that should hardly ever happen, so little
potential performance should be lost.
Of course, if you can show that this happens often / in important
cases, that'd be different.