From owner-freebsd-current@FreeBSD.ORG  Wed Mar  9 17:01:00 2005
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Date: Wed, 9 Mar 2005 17:01:00 +0000
From: Kris Kennaway <kris@FreeBSD.org>
To: Divacky Roman <xdivac02@stud.fit.vutbr.cz>
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cc: current@freebsd.org
Subject: Re: amd64 default CFLAGS
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On Wed, Mar 09, 2005 at 10:27:49AM +0100, Divacky Roman wrote:
> hi,
> 
> why is it necessary (if its at all) to have this: 
> -mfpmath=387 -mno-sse -mno-sse2 -mno-mmx -mno-3dnow in default CFLAGS for amd64
> architecture?

This is the default COPTFLAGS, not CFLAGS, right?  You can't use
special instructions like sse in the kernel because they require extra
register state operations that would cost performance.

Kris