From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40754) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eJzQj-0004Ma-5W for qemu-devel@nongnu.org; Wed, 29 Nov 2017 05:17:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eJzQe-0000AW-Ok for qemu-devel@nongnu.org; Wed, 29 Nov 2017 05:17:25 -0500 Received: from mel.act-europe.fr ([2a02:2ab8:224:1::a0a:d2]:42395 helo=smtp.eu.adacore.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eJzQe-00009a-He for qemu-devel@nongnu.org; Wed, 29 Nov 2017 05:17:20 -0500 References: From: KONRAD Frederic Message-ID: Date: Wed, 29 Nov 2017 11:17:18 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Bug 645662] x87 fpu emulation not accurate enough List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: william lin Cc: qemu-devel@nongnu.org I would write some more basic tests. eg: at instruction level and compare KVM vs TCG mode to find out which trigo instructions are differents (probably not only one). BTW I'm not floating point expert at all :). Fred On 11/29/2017 10:59 AM, william lin wrote: > Hi, > > The goal of the project is to fix the bug. Sorry I should have been more > clear. > > This bug has been around for 7+ years now. Qemu switched to softfloat and > it did not fix this. I think its most likely caused by Qemu's internal > representation not being accurate enough or accuracy lost during > conversion. However this is basically what is given to us in the bug > report, and I have not been able to make much progress past this point, so > we are asking for help. > > Will > > > > On Nov 29, 2017 3:39 AM, "KONRAD Frederic" > wrote: > > Hi, > > I have the same problem here with some of our math testsuites. > It's about some precision issue with trigonometric tests. > > I didn't had time to figure out what happen neither what is > really going wrong. eg: trigonometric function or? > > A quick workaround is to use KVM when possible. > > Fred > > > On 11/29/2017 09:34 AM, william lin wrote: > >> Hello, >> >> I have been looking into this bug >> for a school project, and >> >> after reproducing the bug and tracing through the code, I have run into a >> wall trying to figure out the best way to approach this. If there is anyone >> who is familiar with qemu's fpu and is willing, any tips or suggestions >> will be fantastic. >> >> Thanks, >> >> Will & Wes >> >>