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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: Fri, 29 Dec 2006 23:40:59 -0800
User-agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux)

"Daniel Berlin" <address@hidden> writes:

> Just to address the other compiler issue
>> No, they will work on other compilers, since 'configure'
>> won't use -O2 with those other compilers.
> icc defaults to -O2 without any options, so unless you are passing
> -O0, it will enable this.

Thanks, I didn't know that (I don't use icc).

If -O0 is the only way to convince icc to give us wraparound
arithmetic, then I guess we'll have to default to -O0 for icc.

On the other hand, we haven't had any reports problems with icc in
this area.  So perhaps its optimizations are cleverer, and avoid
the gotchas that beta GCC seems to have blundered into.  In that
case we needn't bother with -O0.

> they make the assumptions during constant folding, and they all
> still constant fold at -O0.

Will this actually cause problems in practice?  I don't see how.

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