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Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."

From: Paul Eggert
Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
Date: Sat, 30 Dec 2006 22:08:57 -0800
User-agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux)

Robert Dewar <address@hidden> writes:

> Of course there is a way out that satisfies both
> sides here, and that is to declare that gcc code
> should adhere to the standard *including* LIA
> and then make sure the default mode of gcc is
> LIA compliant.

Yes, this should solve the problem.  The idea is that -O2
would assume wrapv semantics.  It's fine with me if higher
optimization levels disable -fwrapv by default.

As I understand it the principal argument against this
change is that the performance of some numeric programs
would be adversely affected.  But like you, I doubt whether
it'd affect GCC's performance much, nor would it much affect
the performance of glibc, coreutils, etc., etc.

Also, as I understand it this change shouldn't affect gcc's
SPEC benchmark scores, since they're typically done with -O3
or better.

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