Loop optimizer issues

[Zdenek Dvorak]

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).

Zdenek