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=-0.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D2FBFC3A589 for ; Sun, 18 Aug 2019 21:00:22 +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 963C22184E for ; Sun, 18 Aug 2019 21:00:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WAG9h06i" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 963C22184E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42884 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hzSHl-0005dg-NG for qemu-devel@archiver.kernel.org; Sun, 18 Aug 2019 17:00:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35561) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hzSGX-00052z-RB for qemu-devel@nongnu.org; Sun, 18 Aug 2019 16:59:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hzSGW-0005mH-Iu for qemu-devel@nongnu.org; Sun, 18 Aug 2019 16:59:05 -0400 Received: from mail-ot1-x342.google.com ([2607:f8b0:4864:20::342]:44527) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hzSGW-0005lA-CD; Sun, 18 Aug 2019 16:59:04 -0400 Received: by mail-ot1-x342.google.com with SMTP id w4so14143018ote.11; Sun, 18 Aug 2019 13:59:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=QGUQOX7DG/EeFOoGwh2nTaAPBL77V5yeXpq7T9XE2tU=; b=WAG9h06i2Uj/iUe8bJh07+MQOeI6iZYJkIHYJOwM0dKRuAYb1b1rB8lyihmZtZ3lBe XlgO+PeipCv8HtWl0QfEit4ZEhB7kwnmsxt/vq2RInf+MhqjyZpwArc1viFYwDe6/R+n CPL7CG/5gaKpUmoCfxVKppXO9O9RC+DVCNF8Y9B7V4zxGgZo+GAYGavyYPhZ1xm0DtQs Uhd6oPywQN6zgeBxRs0HJw5LmEI9aFJLOubr/y7y+Afp9RBIO9OR531k4KF02VXcStsJ fspLRKJbSRGcRW2UrCrnOXHmEpcnkIlqp7MsytpBrtO5gFnJDHMC6RZYvP+cHnE8ztEF QeiQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=QGUQOX7DG/EeFOoGwh2nTaAPBL77V5yeXpq7T9XE2tU=; b=g78gqKbP9eJYi5xuHlXHsR9Cgujmdp47UUI5FwjIBHUfqfxJjSpEDc8WsuFttYxv0h HpzcusNn2Js+/wtk17UW5xWlr4s/sr3b7hAKIlG1yvVFBMcJ+8h+Agqp2+ebD3XfY04H Yc0le60W06p/xPclD8lG4sOB/PeM/GElYE0/h0B4CSZFniwSGm1AQ2JcvQAGBvu601Vk HiQaVHsMJkV4WtO5pO9x1ovPVzlH/WxmAKwMqBQndtUlbBzVDQXVNdJyHRrq5xPVrVCI VXBFS72I26nJl4TnoEH8KshE3Jg6lrHa2Vbk+onLsgCgOx/atbLmBpxJCsa3igH5z1cN lfww== X-Gm-Message-State: APjAAAVzGeu8JY4YLWZ3XOE8zvChfydyugVyXufq4HHStzSk5FKreDyF gli0yVtBaKJZlo4pmtkodgCpiyrTIk8g7NIVz6A= X-Google-Smtp-Source: APXvYqxK2whlD69bq4n78HnPWENdN4IFgcW8tqkIcB1D1Bi6njEhmvXkcp9BbKLgPxaGx6n9/MT9Z/dSstd1UBQw2jo= X-Received: by 2002:a9d:1288:: with SMTP id g8mr13004663otg.306.1566161942590; Sun, 18 Aug 2019 13:59:02 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a05:6830:10d7:0:0:0:0 with HTTP; Sun, 18 Aug 2019 13:59:01 -0700 (PDT) Received: by 2002:a05:6830:10d7:0:0:0:0 with HTTP; Sun, 18 Aug 2019 13:59:01 -0700 (PDT) In-Reply-To: <0cfddc22-92ef-3067-9275-8f4f22ca9805@linaro.org> References: <1565983669-6886-1-git-send-email-pc@us.ibm.com> <0cfddc22-92ef-3067-9275-8f4f22ca9805@linaro.org> From: Aleksandar Markovic Date: Sun, 18 Aug 2019 22:59:01 +0200 Message-ID: To: Richard Henderson X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::342 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.23 Subject: Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Paul A. Clarke" , qemu-ppc@nongnu.org, qemu-devel@nongnu.org, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 18.08.2019. 10.10, "Richard Henderson" =D1= =98=D0=B5 =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BE/=D0=BB=D0=B0: > > On 8/16/19 11:59 PM, Aleksandar Markovic wrote: > >> From: "Paul A. Clarke" > ... > >> ISA 3.0B has xscvdpspn leaving its result in word 1 of the target > > register, > >> and mffprwz expecting its input to come from word 0 of the source > > register. > >> This sequence fails with QEMU, as a shift is required between those two > >> instructions. However, the hardware splats the result to both word = 0 > > and > >> word 1 of its output register, so the shift is not necessary. > >> Expect a future revision of the ISA to specify this behavior. > >> > > > > Hmmm... Isn't this a gcc bug (using undocumented hardware feature), given > > everything you said here? > > The key here is "expect a future revision of the ISA to specify this behavior". > > It's clearly within IBM's purview to adjust the specification to document a > previously undocumented hardware feature. > By no means, yes, the key is in ISA documentation. But, the impression that full original commit message conveys is that the main reason for change is gcc behavior. If we accepted in general that gcc behavior determines QEMU behavior, I am afraid we would be on a very slippery slope - therefore I think the commit message (and possible code comment) should, in my opinion, mention ISA docs as the central reason for change. Paul, is there any tentative release date of the new ISA specification? Aleksandar > > r~