From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Emacs using SSE2 on x86 Date: Sat, 4 Jul 2020 09:27:11 -0700 Organization: UCLA Computer Science Department Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="6064"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 To: Emacs Development Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Jul 04 18:29:01 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 1jrl2D-0001SF-7v for ged-emacs-devel@m.gmane-mx.org; Sat, 04 Jul 2020 18:29:01 +0200 Original-Received: from localhost ([::1]:52826 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jrl2C-0002XJ-6C for ged-emacs-devel@m.gmane-mx.org; Sat, 04 Jul 2020 12:29:00 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:50412) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jrl0Y-00086O-Jt for Emacs-devel@gnu.org; Sat, 04 Jul 2020 12:27:18 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:50896) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jrl0W-0002YA-FP for Emacs-devel@gnu.org; Sat, 04 Jul 2020 12:27:18 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 020FD1600EB for ; Sat, 4 Jul 2020 09:27:13 -0700 (PDT) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id cJ73GeLHy4uM for ; Sat, 4 Jul 2020 09:27:12 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 2C21A1600F1 for ; Sat, 4 Jul 2020 09:27:12 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 1n7VDvaCTncZ for ; Sat, 4 Jul 2020 09:27:12 -0700 (PDT) Original-Received: from [192.168.1.9] (cpe-75-82-69-226.socal.res.rr.com [75.82.69.226]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id ECBFD1600EB for ; Sat, 4 Jul 2020 09:27:11 -0700 (PDT) Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= LS0tLS1CRUdJTiBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tCgptUUlOQkV5QWNtUUJFQURB QXlIMnhvVHU3cHBHNUQzYThGTVpFb243NGRDdmM0K3ExWEEySjJ0QnkycHdhVHFmCmhweHhk R0E5Smo1MFVKM1BENGJTVUVnTjh0TFowc2FuNDdsNVhUQUZMaTI0NTZjaVNsNW04c0thSGxH ZHQ5WG0KQUF0bVhxZVpWSVlYL1VGUzk2ZkR6ZjR4aEVtbS95N0xiWUVQUWRVZHh1NDd4QTVL aFRZcDVibHRGM1dZRHoxWQpnZDdneDA3QXV3cDdpdzdlTnZub0RUQWxLQWw4S1lEWnpiRE5D UUdFYnBZM2VmWkl2UGRlSStGV1FONFcra2doCnkrUDZhdTZQcklJaFlyYWV1YTdYRGRiMkxT MWVuM1NzbUUzUWpxZlJxSS9BMnVlOEpNd3N2WGUvV0szOEV6czYKeDc0aVRhcUkzQUZINmls QWhEcXBNbmQvbXNTRVNORnQ3NkRpTzFaS1FNcjlhbVZQa25qZlBtSklTcWRoZ0IxRApsRWR3 MzRzUk9mNlY4bVp3MHhmcVQ2UEtFNDZMY0ZlZnpzMGtiZzRHT1JmOHZqRzJTZjF0azVlVThN Qml5Ti9iClowM2JLTmpOWU1wT0REUVF3dVA4NGtZTGtYMndCeHhNQWhCeHdiRFZadWR6eERa SjFDMlZYdWpDT0pWeHEya2wKakJNOUVUWXVVR3FkNzVBVzJMWHJMdzYrTXVJc0hGQVlBZ1Jy NytLY3dEZ0JBZndoU Content-Language: en-US Received-SPF: pass client-ip=131.179.128.68; envelope-from=eggert@cs.ucla.edu; helo=zimbra.cs.ucla.edu X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/04 11:49:49 X-ACL-Warn: Detected OS = Linux 3.1-3.10 X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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:252671 Archived-At: Bug#42147 reports that Emacs floating-point rounds differently on x86 than on all other platforms, and in its Message #104 I propose a patch to fix this by using GCC's -msse2 -mfpmath=sse options. This patch is needed on GNU/Linux systems; it should be irrelevant on macOS (where SSE2 has always been required) or on MS-Windows development systems (where SSE2 has been the default since 2012). The patch cajoles GCC and similar compilers into using 64-bit floating point instead of erratically substituting 80-bit floating point. Although using 80 bits can improve accuracy, it means the numbers disagree with other platforms and (as Bug#42147 notes) this is more of a problem for Emacs than any lost accuracy. The patch relies on SSE2 instructions on the x86, which were introduced in 2000 and which have by now become universal. I don't see a downside of requiring SSE2 for GCC etc., because as far as I can see, in the GNU/Linux world the only people running 32-bit Emacs on Intelish platforms nowadays are using AMD64 Linux kernels and compiling with 'gcc -m32', and AMD64 requires SSE2 anyway. However, I thought I'd mention this on emacs-devel in case I'm missing something.