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Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
- From: Vincent Lefevre <vincent+gcc at vinc17 dot org>
- To: Robert Dewar <dewar at adacore dot com>
- Cc: Andrew Pinski <pinskia at physics dot uc dot edu>, Gabriel Dos Reis <gdr at integrable-solutions dot net>, Richard Guenther <richard dot guenther at gmail dot com>, Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>, ebb9 at byu dot net, autoconf-patches at gnu dot org, bernds_cb1 at t-online dot de, bug-gnulib at gnu dot org, eggert at cs dot ucla dot edu, gcc at gcc dot gnu dot org
- Date: Sun, 31 Dec 2006 13:09:33 +0100
- Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
- References: <200612310042.kBV0g5pt027400@localhost.localdomain> <45970D3D.1090700@adacore.com>
On 2006-12-30 20:07:09 -0500, Robert Dewar wrote:
> In my view, this comparison optimization should not have been put in
> without justification given that it clearly does affect the semantics
> of real code. Indeed if you really see code like
>
> if (a - 10 < 20)
>
> in place of
>
> if (a < 30)
>
> a very likely explanation is that you are deliberately doing something
> strange with wrap around, and should leave it alone.
I disagree concerning your "very likely explanation". This code
may come from the use of macros, in which case this has nothing
to do with wrap around.
--
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)