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Re: Loop optimizer issues
On Tue, 2003-07-29 at 15:15, Zdenek Dvorak wrote:
> Hello,
>
> > >I think there's been a bit of a disconnect in this discussion.
> > >
> > >Some people are arguing against merging the rtlopt changes into
> > >tree-ssa.
> > >Some people are arguing for merging Zdenek's loop optimizer work into
> > >tree-ssa.
> > >
> > >Nobody, AFAICT, is arguing for merging all of rtlopt into tree-ssa.
> > >
> > >It seems to me that Zdenek is interested in making his loop optimizer
> > >work
> > >at the tree level, and therefore it makes sense to bring it into
> > >tree-ssa.
> > >
> > As long as it's going to work on the tree-ssa SSA form, and not just
> > GIMPLE trees (without SSA), i have no problem with it.
> > If it's not going to work on the SSA form, i'm against it because it
> > would mean that we have three options:
> > 1. Run all loop opts based on the loop optimizer before going into SSA.
> > (Bad)
> > 2. Run all loop opts based on the loop optimizer after going out of SSA
> > (Bad, since we want to lower at some point to allow the optimizers work
> > remove redundant address arithmetic and whatnot)
> > 3. Go into and out of SSA multiple times (expensive).
>
> I don't see a problem with keeping the ssa form (although not
> neccesarily the minimal one).
>
I think Daniel is referring to not just keeping the program in SSA form,
but *using* the SSA form to do the analyses.
Diego.