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Re: What to remove after tree-ssa is merged?
- From: Paul Brook <paul at codesourcery dot com>
- To: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 4 Feb 2004 21:51:08 +0000
- Subject: Re: What to remove after tree-ssa is merged?
- Organization: CodeSourcery
- References: <10402042128.AA04436@vlsi1.ultra.nyu.edu>
On Wednesday 04 February 2004 9:28 pm, Richard Kenner wrote:
> The information must be there somewhere. Whenever these size or bound
> expressions are used, it surely must be in the context of a particular
> object. The RTL expanders manage it quite happily.
>
> When they are *used*, sure. But the point is that they are also present
> in the bounds expressions *to be used* and there is nothing they can be
> substituted with in that context.
To be used when?
I fail to see how this is a problem. The frontend passes complete functions to
the optimizer. I agree that PLACEHOLDER_EXPR is a very useful in the frontend
when building trees. However I can't see how it is of any use once the tree
has been built.
Once the optimizers see a function, haven't we already determined all uses of
these expressions? Do you have any examples of the when an optimier would
unexpectedly decide it needs to use one of these expressions?
Paul