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Re: Loop optimizer issues

On Tuesday, July 29, 2003, at 2:49 PM, Jason Merrill wrote:

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

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).


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