Some thoughts and quetsions about the data flow infrastracture

Richard Kenner
Wed Feb 14 15:11:00 GMT 2007

> 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*.

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