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Re: [tree-ssa] Maintaining/representing def-use/use-def information

From: Daniel Berlin <dberlin at dberlin dot org>
To: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
Cc: Chris Lattner <sabre at nondot dot org>,Jeff Law <law at redhat dot com>,Andrew MacLeod <amacleod at redhat dot com>,gcc mailing list <gcc at gcc dot gnu dot org>
Date: Mon, 15 Dec 2003 16:31:04 -0500
Subject: Re: [tree-ssa] Maintaining/representing def-use/use-def information
References: <1071521234.3257.1817.camel@p4> <Pine.LNX.4.44.0312151502130.27073-100000@nondot.org> <20031215211422.GB27291@atrey.karlin.mff.cuni.cz>

On Dec 15, 2003, at 4:14 PM, Zdenek Dvorak wrote:

Hello,

No, we don't. We don't have any concept of "defining variable" or "versions" at all. Though all SSA construction papers talk about building versions of source variables, once you start doing transformations, that idea becomes quickly meaningless.
except for ssa-pre, that requires the original variable names.

Uh, only to determine lexical equivalence of expressions.

I still
consider it an indication that there is something rotten with the
optimization, but did not get the idea how to make it better so far.

Give me value numbers, and it'll do it based on value numbers.

References:
- Re: [tree-ssa] Maintaining/representing def-use/use-def information
  - From: Andrew MacLeod
- Re: [tree-ssa] Maintaining/representing def-use/use-def information
  - From: Chris Lattner
- Re: [tree-ssa] Maintaining/representing def-use/use-def information
  - From: Zdenek Dvorak

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