From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: VIRT_ADDR_VARIES Date: Thu, 10 Nov 2011 08:50:39 -0800 Organization: UCLA Computer Science Department Message-ID: <4EBC00DF.3010906@cs.ucla.edu> References: <4EB73983.1060000@cs.ucla.edu> <4EB86864.5080709@cs.ucla.edu> <4EB96841.7020701@cs.ucla.edu> <4EB99C7D.8000407@cs.ucla.edu> <4EBABBF5.5030602@cs.ucla.edu> <4EBB8882.6080504@cs.ucla.edu> <4EBBFBF7.2030107@cs.ucla.edu> <83d3d0gc85.fsf@gnu.org> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Trace: dough.gmane.org 1320943853 13744 80.91.229.12 (10 Nov 2011 16:50:53 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Thu, 10 Nov 2011 16:50:53 +0000 (UTC) Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Nov 10 17:50:49 2011 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([140.186.70.17]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ROXpu-0005dC-IS for ged-emacs-devel@m.gmane.org; Thu, 10 Nov 2011 17:50:46 +0100 Original-Received: from localhost ([::1]:55822 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROXpu-000892-58 for ged-emacs-devel@m.gmane.org; Thu, 10 Nov 2011 11:50:46 -0500 Original-Received: from eggs.gnu.org ([140.186.70.92]:59407) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROXpr-00088t-6T for emacs-devel@gnu.org; Thu, 10 Nov 2011 11:50:43 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ROXpq-0003dN-78 for emacs-devel@gnu.org; Thu, 10 Nov 2011 11:50:43 -0500 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:51317) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROXpp-0003d6-7Q; Thu, 10 Nov 2011 11:50:41 -0500 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id CCF1EA60004; Thu, 10 Nov 2011 08:50:39 -0800 (PST) X-Virus-Scanned: amavisd-new at smtp.cs.ucla.edu Original-Received: from smtp.cs.ucla.edu ([127.0.0.1]) by localhost (smtp.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id klYGZSAyCIXZ; Thu, 10 Nov 2011 08:50:39 -0800 (PST) Original-Received: from penguin.cs.ucla.edu (Penguin.CS.UCLA.EDU [131.179.64.200]) by smtp.cs.ucla.edu (Postfix) with ESMTPSA id 79FDEA60001; Thu, 10 Nov 2011 08:50:39 -0800 (PST) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 In-Reply-To: <83d3d0gc85.fsf@gnu.org> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-Received-From: 131.179.128.62 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:145974 Archived-At: On 11/10/11 08:43, Eli Zaretskii wrote: > But why would someone do such a thing? Performance. Comparing against my_edata takes just one instruction. Comparing against both the start and the end of 'pure' takes two comparisons and some glue instructions and typically includes a conditional branch. The optimization I've suggested in this thread prunes away most of this underbrush, but it's still one more instruction (a 'subtract') over the my_edata approach.