From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=56329 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1PZ2ZA-0000Ec-1v
	for qemu-devel@nongnu.org; Sat, 01 Jan 2011 09:36:21 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <bounces@canonical.com>) id 1PZ2Z8-0003Dr-I5
	for qemu-devel@nongnu.org; Sat, 01 Jan 2011 09:36:19 -0500
Received: from adelie.canonical.com ([91.189.90.139]:46115)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <bounces@canonical.com>) id 1PZ2Z8-0003Cu-BE
	for qemu-devel@nongnu.org; Sat, 01 Jan 2011 09:36:18 -0500
Received: from loganberry.canonical.com ([91.189.90.37])
	by adelie.canonical.com with esmtp (Exim 4.69 #1 (Debian))
	id 1PZ2Z4-0002cd-H4
	for <qemu-devel@nongnu.org>; Sat, 01 Jan 2011 14:36:14 +0000
Received: from loganberry.canonical.com (localhost [127.0.0.1])
	by loganberry.canonical.com (Postfix) with ESMTP id B71F22E80FB
	for <qemu-devel@nongnu.org>; Sat,  1 Jan 2011 14:35:53 +0000 (UTC)
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
Date: Sat, 01 Jan 2011 14:29:37 -0000
From: Aurelien Jarno <aurel32@debian.org>
Sender: bounces@canonical.com
References: <20100813182831.6211.99844.malonedeb@palladium.canonical.com>
Message-Id: <20110101142937.19993.5310.launchpad@palladium.canonical.com>
Errors-To: bounces@canonical.com
Subject: [Qemu-devel] [Bug 617528] Re: Incorrect translation of unary
	PPC/SPE instructions (efdneg etc.)
Reply-To: Bug 617528 <617528@bugs.launchpad.net>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: qemu-devel@nongnu.org

** Changed in: qemu
       Status: New =3D> Fix Committed

-- =

You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/617528

Title:
  Incorrect translation of unary PPC/SPE instructions (efdneg etc.)

Status in QEMU:
  Fix Committed

Bug description:
  The translation for the following PPC/SPE (e500) instructions is wrong in=
 QEMU git 6cbf4c8c:

    evfsabs, evfsnabs, evfsneg
    efdabs, efdnabs, efdneg
    efsabs, efsnabs, efsneg

As you can see from the provided patch, these ought to write their result t=
o the destination register (rD) and not modify the source register (rA) in-=
place.

It's rather hard to generate a test-case for this with GCC, since it likes =
to put the input and output of a unary operation into the same registers (t=
hat's probably also the reason why this went unnoticed). There is however a=
 broken code path in the EGLIBC function for sin() when compiled for e500v2=
. It returns nonsense results for e.g. -1.0. Trivial test code follows:

    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>

    int main(int argc, char **argv)
    {
      double x =3D strtod(argv[1], NULL);
      printf("%.14g\n", sin(x));
      return 0;
    }

Result before the patch (WRONG):

$ qemu-ppc -cpu e500v2 sintest -1.0
-1

Result after the patch (OK):

$ qemu-ppc -cpu e500v2 sintest -1.0
-0.84147071838379

A self-contained test-case using inline assembler can be provided upon requ=
est.