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mail-complaints-to="usenet@ciao.gmane.io" Cc: Stefan Monnier , andrea_corallo@yahoo.it, 42147@debbugs.gnu.org To: Paul Eggert Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sat Jul 04 21:03:37 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 1jrnRo-0000S0-C7 for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 04 Jul 2020 21:03:37 +0200 Original-Received: from localhost ([::1]:52492 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jrnRn-0002iM-Cw for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 04 Jul 2020 15:03:35 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:46350) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jrnRK-00022d-0v for bug-gnu-emacs@gnu.org; Sat, 04 Jul 2020 15:03:06 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:48125) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jrnRJ-0008Rq-Ny for bug-gnu-emacs@gnu.org; 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Sat, 04 Jul 2020 15:02:03 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1593889310; bh=grPEC7EtHPcWRQyMymkoSZEYyIjcxk7kVN6l+JgCARU=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=qPjnhypqmoKZ/QQ8RHnGJTV1Y0AzOlGGJlOpeOjEgL/lyMVlg7Oj9KV0FGD12DSlf QiXiMFkyv9uvD61NmgnUMKuAa/zbWaxocnxybTkb549/xeXsf/qGaM2uboepU/sqAp PUZCANYepk3jersO2zHKVW+B/8cNXTZ9EZoG6Q+s= 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 064J1kpZ022785; Sat, 4 Jul 2020 19:01:48 +0000 In-Reply-To: <6d8ba3b1-86b8-3dc8-3d80-17222d436b80@cs.ucla.edu> X-Mailer: Apple Mail (2.3445.104.14) X-CTCH-RefID: str=0001.0A782F1B.5F00D21E.0014, 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=9F_n0buN2XNRkDZ1WxMA:9 a=CjuIK1q_8ugA:10 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:182713 Archived-At: 4 juli 2020 kl. 19.00 skrev Paul Eggert : > Not as far as I know. GCC's -fexcess-precision=3Dstandard option tries = to do that, > by causing GCC to convert 80-bit results to 64-bit results after every = 80-bit > operation. Not quite after every operation: y =3D x * a + b; With -fexcess-precision=3Dstandard, the 80-bit result of the = multiplication will be used in the addition. With -ffloat-store, a = 64-bit store and reload will take place between the two operations, = forcing excess fraction bits to be discarded. Another option is to set the Precision Control field in the x87 control = word to 53-bit precision; that pretty much eliminates double rounding, = but still uses the extended exponent range (only matters in overflow and = underflow cases). And it may confuse libc's carefully crafted = floating-point functions.