Re: gcc/libm floating-point bug?

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From
David Schultz <das@FreeBSD.ORG>
Date
22 May 2003 12:08:22
Subject
Re: gcc/libm floating-point bug?
Message-ID
20030522190817.GB2295@HAL9000.homeunix.com

In reply to

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On Thu, May 22, 2003, Anti wrote:
>
> > > I feel some will screem if we take away the ability to use
> > > -march=pentium4 in places they know for sure will work. Unix is about
> > > mechanisms, not policy.
> >
> > Well, we've got a compiler here with a broken mechanism. Deciding whether or
> > not to act on it sounds like a policy decision to me. I just hope 5.1
> > doesn't get shipped with such an easy way to break stuff.
>
>
> p4 should expand to "-march=pentium4 -mno-sse2" (could set it to pentium3, but
> then people would see pentium3 being used when they specified p4 and think it's
> a bug)...
>
> any educated person with a legit reason to use -march=pentium4 without disabling
> sse2 can always add it to CFLAGS instead of setting it in CPUTYPE...
>
> don't see why anyone wouldn't want to put an end to all the breakage and bug
> reports due to this when the fix is so simple and of no real harm...

When I last checked, -march=pentium4 was slower than
-march=pentium3, and -msse2 was pretty much a wash in terms of
performance, even though SSE2 shaved a few bytes off of FP code
size. This implies that downgrading to -march=pentium3 is the
better option, unless our goal is to dupe people who don't know
well enough to read the documentation.


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