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Re: [PATCH] Fix optimization regression in constant folder

From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
To: matz at suse dot de
Cc: ebotcazou at adacore dot com, gcc-patches at gcc dot gnu dot org, iant at google dot com, mark at codesourcery dot com, richard dot guenther at gmail dot com
Date: Thu, 11 Oct 2007 16:08:46 EDT
Subject: Re: [PATCH] Fix optimization regression in constant folder
References: <200709171539.26653.ebotcazou@adacore.com> <200709301801.39718.ebotcazou@adacore.com> <m3r6kf3gyx.fsf@localhost.localdomain> <200710010127.59677.ebotcazou@adacore.com> <m3abr33dbp.fsf@localhost.localdomain> <10710010056.AA15609@vlsi1.ultra.nyu.edu> <Pine.LNX.4.64.0710010325340.23011@wotan.suse.de> <10710010257.AA21585@vlsi1.ultra.nyu.edu> <Pine.LNX.4.64.0710010454060.23011@wotan.suse.de> <10710010344.AA22633@vlsi1.ultra.nyu.edu> <470D0C50.4080506@codesourcery.com> <Pine.LNX.4.64.0710111658530.23011@wotan.suse.de> <10710111536.AA24058@vlsi1.ultra.nyu.edu> <Pine.LNX.4.64.0710111756080.23011@wotan.suse.de> <10710111616.AA25194@vlsi1.ultra.nyu.edu> <Pine.LNX.4.64.0710111828400.23011@wotan.suse.de> <10710111651.AA26098@vlsi1.ultra.nyu.edu> <Pine.LNX.4.64.0710111853060.23011@wotan.suse.de> <m3r6k13728.fsf@localhost.localdomain> <Pine.LNX.4.64.0710112128460.23011@wotan.suse.de>

> Ehh?  Above I'm explicitely showing why the transformation is _not_ fine, 
> yet you read it as the opposite?

It *is* fine because we know that the overflow that would prevent the
transformation from being valid can't happen for valid programs.  You
always need to go back to what sizetypes are supposed to represent to
decide whether a transformation is valid or not.

References:
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Ian Lance Taylor
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Richard Kenner
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Richard Kenner
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Richard Kenner
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Mark Mitchell
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Richard Kenner
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Richard Kenner
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Richard Kenner
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Ian Lance Taylor
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Michael Matz

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