From owner-freebsd-hackers Thu Nov 9 03:23:46 1995 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id DAA07321 for hackers-outgoing; Thu, 9 Nov 1995 03:23:46 -0800 Received: from tfs.com (tfs.com [140.145.250.1]) by freefall.freebsd.org (8.6.12/8.6.6) with SMTP id DAA07313 for ; Thu, 9 Nov 1995 03:23:35 -0800 Received: from critter.tfs.com by tfs.com (smail3.1.28.1) with SMTP id m0tDV3U-0003viC; Thu, 9 Nov 95 03:22 PST Received: from localhost (localhost [127.0.0.1]) by critter.tfs.com (8.6.11/8.6.9) with SMTP id LAA06541; Thu, 9 Nov 1995 11:02:52 +0100 X-Authentication-Warning: critter.tfs.com: Host localhost didn't use HELO protocol To: "Amancio Hasty Jr." cc: Luigi Rizzo , koshy@blr.novell.com, freebsd-hackers@freebsd.org Subject: Re: Load/Store using FPU regs ... In-reply-to: Your message of "Thu, 09 Nov 1995 02:59:42 PST." <199511091059.CAA03746@rah.star-gate.com> Date: Thu, 09 Nov 1995 11:02:52 +0100 Message-ID: <6539.815911372@critter.tfs.com> From: Poul-Henning Kamp Sender: owner-hackers@freebsd.org Precedence: bulk > >>> Luigi Rizzo said: > > > > Now, I'm not sure if this approach can be used across all processors. > > > > Some FPU's could raise exceptions if illegal bit-patterns are loaded > > > > into its registers. The x86 FPU in particular has very few registers > > > > and a LIFO access pattern for loads and stores so I don't know if the > > > > same trick would work well for it. > > > > > > Not to mention that you might not have a FPU. > > > > So what ? You still have the FPU emulator :) > > Just ignore Pohl's comment we can probably figure out a clever way > to find out if we have a FPU . sure, there's a flag in the kernel, and it's a sysctl var too. > What would be nice to see is if there is indeed a performance gain > by using the floating point instructions if there is for sure I will > use it. The place to use it would be in the Copy-On-Write and Demand-Zero parts of the VM system. -- Poul-Henning Kamp | phk@FreeBSD.ORG FreeBSD Core-team. http://www.freebsd.org/~phk | phk@login.dknet.dk Private mailbox. whois: [PHK] | phk@ref.tfs.com TRW Financial Systems, Inc. Future will arrive by its own means, progress not so.