From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.devel Subject: Re: HAVE_FAST_UNALIGNED_ACCESS Date: Thu, 30 Mar 2023 12:28:30 +0200 Message-ID: <87A3D742-5B8B-4F6B-805B-67AB8B4ECFF5@acm.org> References: <87sfdmlgzx.fsf@gmail.com> Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.14\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="15267"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org, Po Lu To: Robert Pluim Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Thu Mar 30 12:29:11 2023 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 1phpWo-0003mY-Vh for ged-emacs-devel@m.gmane-mx.org; Thu, 30 Mar 2023 12:29:11 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1phpWL-0002jg-Gi; Thu, 30 Mar 2023 06:28:41 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1phpWJ-0002jT-Nw for emacs-devel@gnu.org; Thu, 30 Mar 2023 06:28:39 -0400 Original-Received: from mail1448c50.megamailservers.eu ([91.136.14.48] helo=mail265c50.megamailservers.eu) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1phpWH-00038M-E0 for emacs-devel@gnu.org; Thu, 30 Mar 2023 06:28:39 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1680172113; bh=vse3lTxWJ2r0xQ4QagT8bFDRX+b5jLkqgE5S0UJn8sE=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=KL/hMOfBQavuislYtj91EA3J7ZLXPnq1E6kWhFlNcOcB3UbTKB5I78zZyNuW8toGn UCqokV1NCCHKJ42Xhsu7FFHYw1SUFckFZQuR1P3w4UduFL5BT6eB4ppRUBpLdLVcgR stn0L6SbiHL8VpHZZPU8Upl/KGDqgNMSO6fCb9tI= Feedback-ID: mattiase@acm.or Original-Received: from smtpclient.apple (c188-150-165-235.bredband.tele2.se [188.150.165.235]) (authenticated bits=0) by mail265c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 32UASU2Z022084; Thu, 30 Mar 2023 10:28:32 +0000 In-Reply-To: <87sfdmlgzx.fsf@gmail.com> X-Mailer: Apple Mail (2.3654.120.0.1.14) X-VADE-SPAMSTATE: clean X-VADE-SPAMSCORE: -100 X-VADE-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedvhedrvdehkedgvdejucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecujffquffvqffrkfetpdfqfgfvpdfgpfggqdevhedtnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpegtggfuhfgjffevgffkfhfvofesthhqmhdthhdtvdenucfhrhhomhepofgrthhtihgrshcugfhnghguvghgnohrugcuoehmrghtthhirghsvgesrggtmhdrohhrgheqnecuggftrfgrthhtvghrnhepveekffdujefhkeehvdfgffeikefghfefvdekueffleegfeekueelhfejieefkefgnecukfhppedukeekrdduhedtrdduieehrddvfeehnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepudekkedrudehtddrudeihedrvdefhedphhgvlhhopehsmhhtphgtlhhivghnthdrrghpphhlvgdpmhgrihhlfhhrohhmpehmrghtthhirghsvgesrggtmhdrohhrghdpnhgspghrtghpthhtohepfedprhgtphhtthhopehrphhluhhimhesghhmrghilhdrtghomhdprhgtphhtthhopegvmhgrtghsqdguvghvvghlsehgnhhurdhorhhgpdhrtg hpthhtoheplhhurghnghhruhhoseihrghhohhordgtohhm X-Origin-Country: SE Received-SPF: softfail client-ip=91.136.14.48; envelope-from=mattiase@acm.org; helo=mail265c50.megamailservers.eu X-Spam_score_int: -11 X-Spam_score: -1.2 X-Spam_bar: - X-Spam_report: (-1.2 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, SPF_HELO_NONE=0.001, SPF_SOFTFAIL=0.665 autolearn=no 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-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:304854 Archived-At: 30 mars 2023 kl. 11.34 skrev Robert Pluim : > but even if unaligned access is normally permitted by a machine, it is > still undefined behavior to dereference an unaligned pointer. That's not necessarily a problem; we have plenty of formally undefined = behaviour. What's important is whether we can be confident that it = works. > Instead, HAVE_FAST_UNALIGNED_ACCESS and UNALIGNED_LOAD_SIZE should be > removed and memcpy used instead: No, this isn't something we should be doing at all unless the platform = allows fast unaligned access. Ideally we shouldn't do any of this nonsense but I haven't worked out = how to get the autovectorisers to kick in. > Emacs currently > crashes when built with various compilers performing pointer alignment > checks. Which compilers, exactly?