From owner-freebsd-alpha Tue Dec 14 15:20:29 1999 Delivered-To: freebsd-alpha@freebsd.org Received: from uni4nn.gn.iaf.nl (osmium.gn.iaf.nl [193.67.144.12]) by hub.freebsd.org (Postfix) with ESMTP id 128AA152F9 for ; Tue, 14 Dec 1999 15:20:26 -0800 (PST) (envelope-from wilko@yedi.iaf.nl) Received: from yedi.iaf.nl (uucp@localhost) by uni4nn.gn.iaf.nl (8.9.2/8.9.2) with UUCP id XAA26446; Tue, 14 Dec 1999 23:31:31 +0100 (MET) Received: (from wilko@localhost) by yedi.iaf.nl (8.9.3/8.9.3) id AAA77553; Wed, 15 Dec 1999 00:00:00 +0100 (CET) (envelope-from wilko) Date: Wed, 15 Dec 1999 00:00:00 +0100 From: Wilko Bulte To: Jason Thorpe Cc: FreeBSD-alpha mailing list Subject: Re: use of -mcpu=21164a Message-ID: <19991215000000.B77327@yedi.iaf.nl> References: <199912142214.OAA00903@lestat.nas.nasa.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0i In-Reply-To: <199912142214.OAA00903@lestat.nas.nasa.gov>; from thorpej@nas.nasa.gov on Tue, Dec 14, 1999 at 02:14:45PM -0800 X-OS: FreeBSD yedi.iaf.nl 3.3-STABLE FreeBSD 3.3-STABLE X-PGP: finger wilko@freebsd.org Sender: owner-freebsd-alpha@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Tue, Dec 14, 1999 at 02:14:45PM -0800, Jason Thorpe wrote: > On Tue, 14 Dec 1999 22:47:29 +0100 > Wilko Bulte wrote: > > > > Also, your assembler has to do the right thing; gas will treat the BWX > > > instructions are macros and open-code the equivalent in EV4 instructions > > > unless it is explicitly in EV56 (or greater) mode. > > > > So, in case of -mcpu=21164a gas will generate BWX and if -mcpu=21164a > > is omitted it will open-code in EV4 instructions? > > Yes. (Of course, I'd rather it emitted an error, or a warning, at least...) > > > what if I generate 'netboot' on a Miata with mcpu=m21164a and want to > > use the generated netboot on a Sandpiper (EV4)? There is no kernel (yet) > > to emulate BWX so I lose, right? > > Right, if the compiler/assembler emitted BWX, you lose. This is definitely a nice pitfall. The only obvious way to avoid it (that I see right now) is to have the build environment of the standalone parts of the system set their own cpu-independent flags (read: the least-common denominator cpu). The standalone bits then also include the kernel itself (or can it emulate missing BWX while they are being used inside the kernel? I doubt it.) W/ -- Wilko Bulte Arnhem, The Netherlands - The FreeBSD Project WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message