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=-0.7 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 8A3F1C4360C for ; Thu, 26 Sep 2019 16:26:54 +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 61FE721D56 for ; Thu, 26 Sep 2019 16:26:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 61FE721D56 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ilande.co.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40426 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iDWbV-0001eS-KC for qemu-devel@archiver.kernel.org; Thu, 26 Sep 2019 12:26:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37996) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iDWR8-0006Wf-74 for qemu-devel@nongnu.org; Thu, 26 Sep 2019 12:16:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iDWR6-0005Ou-RQ for qemu-devel@nongnu.org; Thu, 26 Sep 2019 12:16:10 -0400 Received: from indium.canonical.com ([91.189.90.7]:49006) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iDWR6-0005Mg-Le for qemu-devel@nongnu.org; Thu, 26 Sep 2019 12:16:08 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1iDWR2-00058y-4O for ; Thu, 26 Sep 2019 16:16:04 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 749FF2E818D for ; Thu, 26 Sep 2019 16:16:00 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Thu, 26 Sep 2019 16:00:45 -0000 From: Mark Cave-Ayland To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Tags: ppc64 testcase X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: 7-pc mark-cave-ayland philmd X-Launchpad-Bug-Reporter: Paul Clarke (7-pc) X-Launchpad-Bug-Modifier: Mark Cave-Ayland (mark-cave-ayland) References: <156711057074.6835.13599471410604217618.malonedeb@soybean.canonical.com> Message-Id: <156951364519.19582.47657564321527870.malone@wampee.canonical.com> Subject: [Bug 1841990] Re: instruction 'denbcdq' misbehaving 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="19056"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: cb03eee1bab620acad134b56651b11af95f36644 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 91.189.90.7 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 1841990 <1841990@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Right so this looks like a different bug: if you look at helper_bcdadd() and helper_bcdsub() in target/ppc/int_helper.c then you can see the problem straight away: the code is accessing the elements of ppc_avr_t without directly without using the VsrX() macros which correct for host endian. Fortunately the fix is really easy - replace the direct access with the relevant VsrX() macro from target/ppc/cpu.h instead. It does look as if there are several places in the BCD code that need fixing up though. The first thing to fix is the #define BCD_DIG_BYTE around line 2055: the VsrX() macro offsets are in "big-endian" format to match the ISA specification so VsrD(0) is the MSB and VsrD(1) is the LSB, which means that during the conversion you generally want the index from within the #if defined(HOST_WORDS_BIGENDIAN) ... #endif section. Given that the VsrX() macros invert the array index according to host endian then you can completely remove everything between #if defined(HOST_WORDS_BIGENDIAN) ... #endif and replace it with simply: #define BCD_DIG_BYTE(n) (15 - ((n) / 2)) Then as an example in the bcd_get_sgn() function below you can change the switch from: switch (bcd->u8[BCD_DIG_BYTE(0)] & 0xF) to: switch (bcd->VsrB(BCD_DIG_BYTE(0)) & 0xF) etc. and repeat for the remaining bcd helpers down to helper_vsbox() around line 2766. Note it seems the last few bcd helpers have a #if defined(HOST_WORDS_BIGENDIAN) ... #endif section towards the start that might a bit of thought, however once they are written in terms of the VsrX() macros then everything will "just work" regardless of host endian. -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1841990 Title: instruction 'denbcdq' misbehaving Status in QEMU: New Bug description: Instruction 'denbcdq' appears to have no effect. Test case attached. On ppc64le native: -- gcc -g -O -mcpu=3Dpower9 bcdcfsq.c test-denbcdq.c -o test-denbcdq $ ./test-denbcdq 0x00000000000000000000000000000000 0x0000000000000000000000000000000c 0x22080000000000000000000000000000 $ ./test-denbcdq 1 0x00000000000000000000000000000001 0x0000000000000000000000000000001c 0x22080000000000000000000000000001 $ ./test-denbcdq $(seq 0 99) 0x00000000000000000000000000000064 0x0000000000000000000000000000100c 0x22080000000000000000000000000080 -- With "qemu-ppc64le -cpu power9" -- $ qemu-ppc64le -cpu power9 -L [...] ./test-denbcdq 0x00000000000000000000000000000000 0x0000000000000000000000000000000c 0x0000000000000000000000000000000c $ qemu-ppc64le -cpu power9 -L [...] ./test-denbcdq 1 0x00000000000000000000000000000001 0x0000000000000000000000000000001c 0x0000000000000000000000000000001c $ qemu-ppc64le -cpu power9 -L [...] ./test-denbcdq $(seq 100) 0x00000000000000000000000000000064 0x0000000000000000000000000000100c 0x0000000000000000000000000000100c -- I started looking at the code, but I got confused rather quickly. Could be related to endianness? I think denbcdq arrived on the scene before little-endian was a big deal. Maybe something to do with utilizing implicit floating-point register pairs... I don't think the right data is getting to helper_denbcdq, which would point back to the gen_fprp_ptr uses in dfp-impl.inc.c (GEN_DFP_T_FPR_I32_Rc). (Maybe?) To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1841990/+subscriptions