Re: [PATCH][RFT] Optimization pass-pipeline re-organization [3/n]

[Richard Guenther <rguenther at suse dot de>]

On Mon, 18 Aug 2008, Jeff Law wrote:

> Richard Guenther wrote:
> > 
> > The most interesting pass change is the removal of the first
> > DOM/phi-cprop pair.  DOM mostly deals with jump-threading at this
> > place and for tramp3d catches 473 threads on top of the 2555 ones
> > performed by the VRP pass that runs right before the first DOM.
> >   
> Ultimately, jump threading is all I really want DOM to do long term anyway --

Yes, I agree ..

> the redundancy elimination performed by DOM can be better handled elsewhere.
> The interesting question is there redundancy elimination left in DOM that is
> unique and if not, can we get the same overall effect if we remove the
> redundancy elimination from DOM and instead using existing passes for
> redundancy elimination.  Same overall effect doesn't mean identical code, but

... though I am not sure (I didn't investigate) how much of the
redundancy elimination code feeds the jump threading parts.  I was
thinking of moving the jump threading parts over to SCCVN instead, given
that VRP lacks capabilities regarding to symbolical conditions.

> reasonably close and without incurring a significant compile-time hit.
> 
> Regardless, I fully support eliminating the number of calls into DOM as well
> as trimming the set of transformations performed by DOM.

Thanks.  It seems the last DOM pass doesn't do very much as well, so
I'll be playing with removing that as a last step of cleaning up the
pipeline.  Even if that might need another run of FRE instead of DOM.

Richard.