Skip site navigation (1)Skip section navigation (2)
Date:      Tue, 10 Feb 2004 14:38:11 -0800
From:      Kris Kennaway <kris@obsecurity.org>
To:        Roop Nanuwa <roop@hqst.com>
Cc:        questions@FreeBSD.org
Subject:   Re: How about them optimizations?
Message-ID:  <20040210223810.GA42056@xor.obsecurity.org>
In-Reply-To: <40293BB6.5060005@hqst.com>
References:  <40293BB6.5060005@hqst.com>

next in thread | previous in thread | raw e-mail | index | archive | help

--9jxsPFA5p3P2qPhR
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Tue, Feb 10, 2004 at 12:14:46PM -0800, Roop Nanuwa wrote:
> Part of my current /etc/make.conf on my 5.2-CURRENT box looks like:
>=20
> CPUTYPE=3D athlon-xp
> CFLAGS=3D -O2 -pipe -fomit-frame-pointer -mmmx -msse -m3dnow -mfpmath=3Ds=
se
> COPTFLAGS=3D -O -pipe
>=20
> Now what I'm wondering is if those extras like mmmx msse actually do=20
> anything. The
> only reason they're in there is because I saw them on a website about=20
> what people
> use to optimize gentoo. I had nothing better to do so I recompiled the=20
> world with
> them. I didn't really notice anything good or bad happening after that.=
=20
> I did have
> to mess around with a couple of makefiles to get around the=20
> strict-aliasing problem
> that O2 introduces. Besides that, though, are there any advantages or=20
> disadvantages
> to compiling with those optimizations and switches?
>=20
> Does -mfpmath=3Dsse actually do anything relevent for the FreeBSD world? =
I=20
> know
> what the GCC manual says about it but I'd rather hear some real world inf=
o.
>=20
> An enquiring mind wants to know.

That's superfluous, because gcc already uses all available opcodes
when you tell it to optimize for your CPU type with CPUTYPE=3Dathlon-xp.
Using -O2 is recommended against, though - see the sample make.conf
file.

Kris

--9jxsPFA5p3P2qPhR
Content-Type: application/pgp-signature
Content-Disposition: inline

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (FreeBSD)

iD8DBQFAKV1SWry0BWjoQKURAq3vAJ4+QNVcX8shBTojIK6bKYozInvl9wCdFcMx
ov0d+TCu+1p1xBtCaaWTLKo=
=4EWQ
-----END PGP SIGNATURE-----

--9jxsPFA5p3P2qPhR--



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20040210223810.GA42056>