Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261920AbVE0Hpz (ORCPT ); Fri, 27 May 2005 03:45:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261943AbVE0HbH (ORCPT ); Fri, 27 May 2005 03:31:07 -0400 Received: from aun.it.uu.se ([130.238.12.36]:59093 "EHLO aun.it.uu.se") by vger.kernel.org with ESMTP id S261920AbVE0HZk (ORCPT ); Fri, 27 May 2005 03:25:40 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17046.52070.257018.186057@alkaid.it.uu.se> Date: Fri, 27 May 2005 09:25:26 +0200 From: Mikael Pettersson To: Cc: Subject: Re: 387 emulator hack - mutant AAD trick - any objections? In-Reply-To: <000701c5628b$583f8060$2800000a@pc365dualp2> References: <000701c5628b$583f8060$2800000a@pc365dualp2> X-Mailer: VM 7.17 under Emacs 20.7.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1022 Lines: 23 cutaway@bellsouth.net writes: > Will there be any objections to using a quasi-documented mutation of the > x86's AAD instruction in the 387 emulator? Every CPU around has to do this > mutation correctly or a LOT of existing code will break... > > The performance of storing to user space of BCD numbers in the 387 emulator > code could be improved significantly by using the mutant AAD instruction > trick (i.e. alter its implicit base from 10 to 16). See reg_ld_str.c, in > function FPU_store_bcd() What do you mean by "quasi-documented" and "mutant"? Intel certainly documents the "D5 ib" form as being a valid way to change the base from the default 10. The only issue AFAIK is that assemblers may only recognise the plain base-10 AAD syntax. No biggie. /Mikael - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/