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: __builtin_assume warnings Date: Wed, 19 Aug 2020 10:01:04 +0200 Message-ID: <538D98E3-DCE7-4A6C-B1AC-B00253E1CCA1@acm.org> References: <8e65e2a9-1058-3084-7f8d-8439fa908fb3@cs.ucla.edu> <1da4c4ff-f057-f4ac-c3ec-3232bc0a4477@cs.ucla.edu> <25e394e9-0e6e-7794-3e90-5fbab3951678@cs.ucla.edu> Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.15\)) 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="23300"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Wed Aug 19 10:02:45 2020 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 1k8J3V-0005yi-F0 for ged-emacs-devel@m.gmane-mx.org; Wed, 19 Aug 2020 10:02:45 +0200 Original-Received: from localhost ([::1]:37488 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8J3U-0004Th-Gy for ged-emacs-devel@m.gmane-mx.org; Wed, 19 Aug 2020 04:02:44 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:53020) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8J2D-0003Ig-43 for emacs-devel@gnu.org; Wed, 19 Aug 2020 04:01:25 -0400 Original-Received: from mail153c50.megamailservers.eu ([91.136.10.163]:52270 helo=mail50c50.megamailservers.eu) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8J29-00070J-5x for emacs-devel@gnu.org; Wed, 19 Aug 2020 04:01:24 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1597824067; bh=akrBWB5AzEiIk1g4ZulK/JeCHaRL/uxsmRvPPV/9kkE=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=KFd2k1N2aybkZggU/SJ1srfvmQVz6ZBJE0ilSL1W12u44A8lXtIigu5aAzp37/w61 NvOVSLJWBmjudCPC1UC3jlm1o+D2+xXFwT7s9kHcsNy/y/eDZUYGi+NPH9f/SkDUER ikvjFW4Jf/l2vyDIAFH3y5h+W047V8nkaKReze+w= Feedback-ID: mattiase@acm.or Original-Received: from [192.168.0.4] (c188-150-171-71.bredband.comhem.se [188.150.171.71]) (authenticated bits=0) by mail50c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 07J814lf017612; Wed, 19 Aug 2020 08:01:07 +0000 In-Reply-To: <25e394e9-0e6e-7794-3e90-5fbab3951678@cs.ucla.edu> X-Mailer: Apple Mail (2.3445.104.15) X-CTCH-RefID: str=0001.0A782F1B.5F3CDC43.008C, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: 0.000 X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-CSC: 0 X-CHA: v=2.3 cv=NoevjPVJ c=1 sm=1 tr=0 a=SF+I6pRkHZhrawxbOkkvaA==:117 a=SF+I6pRkHZhrawxbOkkvaA==:17 a=kj9zAlcOel0A:10 a=M51BFTxLslgA:10 a=RiguqLAv5m94oVpF4zUA:9 a=CjuIK1q_8ugA:10 X-Origin-Country: SE Received-SPF: softfail client-ip=91.136.10.163; envelope-from=mattiase@acm.org; helo=mail50c50.megamailservers.eu X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 04:01:18 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x (no timestamps) [generic] 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, URIBL_BLOCKED=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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:253988 Archived-At: 19 aug. 2020 kl. 00.53 skrev Paul Eggert : > No, it's the other way around at least for me: having 'assume' use = Clang's __builtin_assume makes 'assume' slower. Without = __builtin_assume, 'assume' falls back on __builtin_unreachable, and = Clang generates better code for __builtin_unreachable than it does = __builtin_assume. Right you are; as far as I can tell, __builtin_assume is strictly less = useful. There does not seem to be any point in using it at this time. = The only advantage over if(!x)__builtin_unreachable() appears to be that = the argument isn't actually evaluated, but I'm not sure when that = property would be useful. Thank you for clearing that up.