From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Miles Bader Newsgroups: gmane.emacs.devel Subject: Re: Untagging by subtraction instead of masking on USE_LSB_TAG Date: Mon, 28 Jan 2008 13:22:38 +0900 Message-ID: References: <87ve5ezjwp.fsf@ambire.localdomain> Reply-To: Miles Bader NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1201494193 31464 80.91.229.12 (28 Jan 2008 04:23:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 28 Jan 2008 04:23:13 +0000 (UTC) Cc: YAMAMOTO Mitsuharu , emacs-devel@gnu.org To: Thien-Thi Nguyen Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Jan 28 05:23:33 2008 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.50) id 1JJLWu-0008NM-Jp for ged-emacs-devel@m.gmane.org; Mon, 28 Jan 2008 05:23:32 +0100 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1JJLWT-0000DO-JH for ged-emacs-devel@m.gmane.org; Sun, 27 Jan 2008 23:23:05 -0500 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1JJLWP-0000D1-4y for emacs-devel@gnu.org; Sun, 27 Jan 2008 23:23:01 -0500 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1JJLWN-0000Cn-Kk for emacs-devel@gnu.org; Sun, 27 Jan 2008 23:23:00 -0500 Original-Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1JJLWN-0000Ck-G1 for emacs-devel@gnu.org; Sun, 27 Jan 2008 23:22:59 -0500 Original-Received: from tyo202.gate.nec.co.jp ([202.32.8.206]) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1JJLWJ-0008CJ-BJ; Sun, 27 Jan 2008 23:22:55 -0500 Original-Received: from relay31.aps.necel.com ([10.29.19.54]) by tyo202.gate.nec.co.jp (8.13.8/8.13.4) with ESMTP id m0S4MdK0016930; Mon, 28 Jan 2008 13:22:39 +0900 (JST) Original-Received: from relay31.aps.necel.com ([10.29.19.16] [10.29.19.16]) by relay31.aps.necel.com with ESMTP; Mon, 28 Jan 2008 13:22:39 +0900 Original-Received: from dhapc248.dev.necel.com ([10.114.112.215] [10.114.112.215]) by relay31.aps.necel.com with ESMTP; Mon, 28 Jan 2008 13:22:39 +0900 Original-Received: by dhapc248.dev.necel.com (Postfix, from userid 31295) id 294085AC; Mon, 28 Jan 2008 13:22:38 +0900 (JST) System-Type: i686-pc-linux-gnu Blat: Foop In-Reply-To: <87ve5ezjwp.fsf@ambire.localdomain> (Thien-Thi Nguyen's message of "Mon, 28 Jan 2008 04:52:22 +0100") Original-Lines: 20 X-detected-kernel: by monty-python.gnu.org: Solaris 8 (1) X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:87681 Archived-At: Thien-Thi Nguyen writes: > For masking, i see offsets (lwz) of 4,0,0 (lines A,B,C). > For subtraction, -1,-5,-5. > > It's very possible that the machine can handle 4,0,0 more > efficiently; those all are even (0, modulo 2) and in two cases > "nothing"! Furthermore, the maximum absolute offset for the > subtraction method is 5, which is larger (faaarther away) than 4. > > Anyway, here is an excerpt from p.532 of "PowerPC 405, Embedded > Processor Core, User's Manual": Note that the important value here is the EA, not the offset. Typically in a LSB tag scheme, the tags are arranged so that after adding these "funny" offsets, the resulting EA is aligned properly. -Miles -- Apologize, v. To lay the foundation for a future offense.