From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Time to merge scratch/correct-warning-pos into master, perhaps? Date: Tue, 25 Jan 2022 08:27:55 -0500 Message-ID: References: <837darmygd.fsf@gnu.org> <58bb8030d59733b52b8d@heytings.org> <83r18zkmd5.fsf@gnu.org> <835yq9ls7j.fsf@gnu.org> <058b682b11240176288f@heytings.org> <83h79tjd2f.fsf@gnu.org> <058b682b11f58780b580@heytings.org> <83v8y8ij39.fsf@gnu.org> <6a5bb5a08b3d764611f9@heytings.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="3507"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) Cc: Gregory Heytings , mattiase@acm.org, Eli Zaretskii , larsi@gnus.org, emacs-devel@gnu.org To: Alan Mackenzie Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Jan 25 16:04:16 2022 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nCNMl-0000gb-38 for ged-emacs-devel@m.gmane-mx.org; Tue, 25 Jan 2022 16:04:15 +0100 Original-Received: from localhost ([::1]:54472 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nCNMk-0005mi-21 for ged-emacs-devel@m.gmane-mx.org; Tue, 25 Jan 2022 10:04:14 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:44520) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nCLrn-0006xy-Di for emacs-devel@gnu.org; Tue, 25 Jan 2022 08:28:12 -0500 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:49965) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nCLrd-0006UQ-Oo; Tue, 25 Jan 2022 08:28:10 -0500 Original-Received: from pmg2.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id 72C9F805F9; Tue, 25 Jan 2022 08:27:58 -0500 (EST) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id F0465805CC; Tue, 25 Jan 2022 08:27:56 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1643117276; bh=cJYQI23IPIIhnTu7oqszz0lkT77tuZAaibipSpAb07k=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=gm66lr2V7lbyLXatxx/0pZ9H7vPFB8Hn54QSF+RmL1ZryeXQYLoYQ322VWvCkG5Gr E1mq7Wsd11sLs017HOWiipcEUD01Qs+uvgeddpRibY87bStvDrxOQn17we0LYPXtYS mIYIjKUUjD2QFhZyD4N1Vr3L60q5IgXoGnGJsyfGtGGIG3KpbwvD0KrEYn9YBl5D0d nJymeahsxzlbOYZ14ELG+YNCElS+V+WOWeEpK0Av8cshI8l78xvTBbBJIXKMnaXs08 k9mCMTkqAk5xAXzdSBEZ6wqNjNtaRvuQWxQG1TlY+Sf2FkXNMcN98gG/vJ0w0Q6zYO TXOYYrbZebAdQ== Original-Received: from ceviche (unknown [216.154.30.173]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id B3BB8120403; Tue, 25 Jan 2022 08:27:56 -0500 (EST) In-Reply-To: (Alan Mackenzie's message of "Tue, 25 Jan 2022 11:27:27 +0000") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:285373 Archived-At: > The C level EQ operation takes twice as long when the operands do not > match, and the same time as before when they do match. I highly doubt reality is that simple because CPU performance is a lot more complex than just counting instructions. > When one of the operands is a literal nil, there is no increase in > execution time. That's an oversimplification as well: it's only when we use the `NILP` macro that the extra cost is avoided. Any use of `EQ` is still slowed down when it happens to receive a nil as one of the arguments. I do find the slowdowns discussed here rather worrisome. I thought the original agreement was that it was OK to install this change if the slowdown could be brought down to about 1% or below (for the non-compilation case). More importantly, I wonder how slowing down EQ by a factor of 2 can end up costing 10% of runtime when running the test suite. I think this deserves investigation. Stefan