> Yes, one possibility is to use a RTX hook for this too. By default you > would return NULL (and this would propagate up); in combine you could > override it to return the CLOBBER.
I really don't see why. Look at when combine calls the simplify routines now. If they return zero, it uses the original value. If the simplify routines do more, that will still be true. I don't see the point in preserving the CLOBBER kludge in an environment that no longer needs it. > To some extent, simplify-rtx.c could *know* about CLOBBER. It *could*, but I think it would be much cleaner if it *didn't*.
