From owner-cvs-all Thu Oct 25 15:49:24 2001 Delivered-To: cvs-all@freebsd.org Received: from anchor-post-33.mail.demon.net (anchor-post-33.mail.demon.net [194.217.242.91]) by hub.freebsd.org (Postfix) with ESMTP id C062A37B405; Thu, 25 Oct 2001 15:49:18 -0700 (PDT) Received: from [62.49.251.130] (helo=herring.nlsystems.com) by anchor-post-33.mail.demon.net with esmtp (Exim 2.12 #1) id 15wtJN-0002i7-0X; Thu, 25 Oct 2001 23:49:17 +0100 Received: from salmon.nlsystems.com (salmon [10.0.0.3]) by herring.nlsystems.com (8.11.2/8.11.2) with ESMTP id f9PMm2708821; Thu, 25 Oct 2001 23:48:02 +0100 (BST) (envelope-from dfr@nlsystems.com) Date: Thu, 25 Oct 2001 23:46:00 +0100 (BST) From: Doug Rabson To: Luigi Rizzo Cc: John Baldwin , Jonathan Lemon , , Subject: Re: cvs commit: src/sys/dev/fxp if_fxp.c In-Reply-To: <20011025151935.G57392@iguana.aciri.org> Message-ID: <20011025234439.M549-100000@salmon.nlsystems.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, 25 Oct 2001, Luigi Rizzo wrote: > > > does it mean that integer multiply in the kernel is bad on the ia64 :) > > > > Not really - its reasonably quick. They just didn't bother to add any > > integer multipliers when there were two perfectly good floating point > > units going idle. Moving integers in and out of float registers is quick > > and easy so it actually makes sense. Divides are done with floating point > > too. > > the point for not having FP in the kernel is not speed, but rather > the fact that you do not have to save those registers in a context > switch. This could just be an artifact of ancient times where FPU's > were separate units... > > So, i guess the FP registers are saved in the IA64 context switch routines ? The kernel only uses a cut-down set of fp registers - ten registers are saved/restored on exceptions and four on context switches. -- Doug Rabson Mail: dfr@nlsystems.com Phone: +44 20 8348 6160 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message