From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.bugs Subject: bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations? Date: Fri, 3 Jul 2020 10:32:56 +0200 Message-ID: References: <3A9CC2A3-8307-47B2-8D80-795C0AF020E1@acm.org> <0433A879-C98D-4B1A-B85C-A15DA9289099@acm.org> <1621669100.2102667.1593639091621@mail.yahoo.com> <775819003.2516724.1593687594435@mail.yahoo.com> <5F2B4684-34D1-4474-8909-9F435369FE54@acm.org> <705260433.2731607.1593698199171@mail.yahoo.com> <6CF8EE58-9A49-40E7-AA86-48AB39BF94BA@acm.org> <28B19D86-343C-4126-B95F-1F38735F73F2@acm.org> <1288c6a5-545b-f68c-ff6b-7683db3e54c1@cs.ucla.edu> Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.14\)) 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="20761"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Stefan Monnier , Andrea Corallo , 42147@debbugs.gnu.org To: Paul Eggert Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Fri Jul 03 10:34:11 2020 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1jrH98-0005GW-2W for geb-bug-gnu-emacs@m.gmane-mx.org; Fri, 03 Jul 2020 10:34:10 +0200 Original-Received: from localhost ([::1]:46890 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jrH97-00008T-1Y for geb-bug-gnu-emacs@m.gmane-mx.org; Fri, 03 Jul 2020 04:34:09 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:53112) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jrH90-000088-Aw for bug-gnu-emacs@gnu.org; Fri, 03 Jul 2020 04:34:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:44843) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jrH90-0006Tx-1H for bug-gnu-emacs@gnu.org; Fri, 03 Jul 2020 04:34:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1jrH8z-0004SB-Ra for bug-gnu-emacs@gnu.org; Fri, 03 Jul 2020 04:34:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Fri, 03 Jul 2020 08:34:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 42147 X-GNU-PR-Package: emacs Original-Received: via spool by 42147-submit@debbugs.gnu.org id=B42147.159376519217061 (code B ref 42147); Fri, 03 Jul 2020 08:34:01 +0000 Original-Received: (at 42147) by debbugs.gnu.org; 3 Jul 2020 08:33:12 +0000 Original-Received: from localhost ([127.0.0.1]:56389 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jrH8C-0004R7-EE for submit@debbugs.gnu.org; Fri, 03 Jul 2020 04:33:12 -0400 Original-Received: from mail78c50.megamailservers.eu ([91.136.10.88]:60490 helo=mail70c50.megamailservers.eu) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jrH87-0004Qu-Hy for 42147@debbugs.gnu.org; Fri, 03 Jul 2020 04:33:11 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1593765182; bh=w28gfoYULD+nGXf7QJeXJ5QbYZqR1WWbH2yWJS34D2E=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=sfm0v7ilZeDRVgO0Kd7RUHvH/UGnGeaYFNRR0ikNEFd9x2NNQiEpTdQAKxYxkjIKw 67OnLPpu5g0ahwZNSZKPG840MfRSEkVnr9tY6uRqUWfwiuSwYVksNoHodvggaddeYP 8JwsKZ6y9bNkno1IF2n3n4aenDCvSrFKmjnevByY= 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 mail70c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 0638WvYW025523; Fri, 3 Jul 2020 08:32:59 +0000 In-Reply-To: <1288c6a5-545b-f68c-ff6b-7683db3e54c1@cs.ucla.edu> X-Mailer: Apple Mail (2.3445.104.14) X-CTCH-RefID: str=0001.0A782F24.5EFEECB9.0069, 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=OKBZIhSB c=1 sm=1 tr=0 a=SF+I6pRkHZhrawxbOkkvaA==:117 a=SF+I6pRkHZhrawxbOkkvaA==:17 a=kj9zAlcOel0A:10 a=M51BFTxLslgA:10 a=2YIUIZ3jAAAA:8 a=ZzRdP2rEuLaPOZdU1cIA:9 a=CjuIK1q_8ugA:10 a=r0Ai7q2SEVf7W-GEcfLe:22 X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:182657 Archived-At: 3 juli 2020 kl. 01.16 skrev Paul Eggert : > As you can see, sometimes SSE2 is closer to the mathematically-correct = answer > and sometimes x87 is. In typical C math code, x87 is better; in Emacs = I imagine > the reverse is true (for the reasons you mentioned), though I have not = attempted > to measure this. Thanks for the examples and these were indeed what I had in mind = (there's also the effect from having a greater exponent range in the = intermediate result); Monniaux [1] is a good reference. In practice, the extra precision of x87 code is so unreliable and fickle = (unless the 80-bit long double is used throughout) that it's almost = never worth it. (Being much slower doesn't help either.) Fortunately modern compilers generate SSE code by default, only passing = return values on the x87 stack as per the x86 ABI (which causes no = harm). This reduces an already tiny risk to nil. We could add an = elaborate configure or run-time test and admonishments to the = installation instructions but frankly we have better use of our time. I = suggest we replace byte-opt--portable-numberp with numberp (or nothing = at all, depending on where it occurs) and be done with it. --- [1] = https://hal.archives-ouvertes.fr/hal-00128124/file/floating-point-article.= pdf