From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E55A4C3A5A3 for ; Tue, 27 Aug 2019 04:18:16 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B27A5206BA for ; Tue, 27 Aug 2019 04:18:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B27A5206BA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=us.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46424 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2Svv-0002Sn-UB for qemu-devel@archiver.kernel.org; Tue, 27 Aug 2019 00:18:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60629) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2StP-0000ui-3X for qemu-devel@nongnu.org; Tue, 27 Aug 2019 00:15:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i2StN-0002gu-VV for qemu-devel@nongnu.org; Tue, 27 Aug 2019 00:15:39 -0400 Received: from indium.canonical.com ([91.189.90.7]:40386) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1i2StN-0002gV-Q5 for qemu-devel@nongnu.org; Tue, 27 Aug 2019 00:15:37 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1i2StL-0002Fl-U8 for ; Tue, 27 Aug 2019 04:15:35 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id E26912E802D for ; Tue, 27 Aug 2019 04:15:35 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 27 Aug 2019 04:06:38 -0000 From: Paul Clarke To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: 7-pc X-Launchpad-Bug-Reporter: Paul Clarke (7-pc) X-Launchpad-Bug-Modifier: Paul Clarke (7-pc) References: <156686849716.6431.16425651381928336460.malonedeb@gac.canonical.com> Message-Id: <156687879834.4807.16452132471732559890.malone@wampee.canonical.com> X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="19031"; Instance="launchpad-lazr.conf" X-Launchpad-Hash: 4419450b03b43853c35b62e962bb01e32683f001 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 91.189.90.7 Subject: [Qemu-devel] [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1841491 <1841491@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Responding to the patch https://lists.nongnu.org/archive/html/qemu- ppc/2019-08/msg00404.html, it seems to work for "double", but not for "float". Test case attached. ** Attachment added: "float testcase" https://bugs.launchpad.net/qemu/+bug/1841491/+attachment/5284810/+files/= test-ffma.c -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1841491 Title: floating point emulation can fail to set FE_UNDERFLOW Status in QEMU: New Bug description: Floating point emulation can fail to set FE_UNDERFLOW in some circumstances. This shows up often in glibc's "math" tests. A similar test is attached. This is similar to bug #1841442, but not the same problem, and I don't think the fix will be in the same code. On ppc64le native: -- $ gcc -c -O2 fma.c $ gcc -O2 test-fma.c fma.o -lm -o test-fma $ ./test-fma $(./test-fma) fma(0x1.ffffffffffffcp-1022, 0x1.0000000000001p-1, 0x0.0000000000001p-102= 2) 0x0 0xa000000 FE_INEXACT FE_UNDERFLOW = 0x1p-1022 -- On qemu-system-ppc64: -- $ ./test-fma $(./test-fma) fma(0x1.ffffffffffffcp-1022, 0x1.0000000000001p-1, 0x0.0000000000001p-102= 2) 0x0 0x2000000 FE_INEXACT = 0x1p-1022 -- QEMU versions vary, but not too much, and are pretty close to git HEAD: - 586f3dced9 (HEAD -> master, origin/master, origin/HEAD) Merge remote-tr= acking branch 'remotes/cohuck/tags/s390x-20190822' into staging - 864ab31 Update version for v4.1.0-rc4 release There are worse symptoms on qemu-x86_64, but this is apparently not surprising per https://bugs.launchpad.net/qemu/+bug/1841442/comments/6. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1841491/+subscriptions