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From: Paul Brook <paul@codesourcery.com>
Organization: CodeSourcery
To: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
Subject: Re: What to remove after tree-ssa is merged?
Date: Wed, 04 Feb 2004 21:51:00 -0000
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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