From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:44038)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rkrcmar@redhat.com>) id 1YTXoS-0002Kk-1F
	for qemu-devel@nongnu.org; Thu, 05 Mar 2015 10:35:48 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <rkrcmar@redhat.com>) id 1YTXoL-0007B7-Gy
	for qemu-devel@nongnu.org; Thu, 05 Mar 2015 10:35:47 -0500
Received: from mx1.redhat.com ([209.132.183.28]:41647)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rkrcmar@redhat.com>) id 1YTXoL-0007Aw-9v
	for qemu-devel@nongnu.org; Thu, 05 Mar 2015 10:35:41 -0500
Date: Thu, 5 Mar 2015 16:35:36 +0100
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Message-ID: <20150305153535.GB3361@potion.redhat.com>
References: <1425479449-11480-1-git-send-email-kraxel@redhat.com>
	<1425479449-11480-4-git-send-email-kraxel@redhat.com>
	<CAE8XmWqz8rkNqNaSWWsVdifT9-hot=Qdv_qZhN_DewqVaQEG1Q@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAE8XmWqz8rkNqNaSWWsVdifT9-hot=Qdv_qZhN_DewqVaQEG1Q@mail.gmail.com>
Subject: Re: [Qemu-devel] [PULL 3/7] qxl: refactor rounding up to a nearest
 power of 2
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/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: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Dongsheng Song <dongsheng.song@gmail.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>, qemu-devel@nongnu.org

2015-03-05 12:57+0800, Dongsheng Song:
> On Wed, Mar 4, 2015 at 10:30 PM, Gerd Hoffmann <kraxel@redhat.com> wrote:
> > +/* round up to the nearest power of 2 (0 if overflow) */
> > +uint64_t pow2ceil(uint64_t value)
> > +{
> > +    uint8_t nlz = clz64(value);
> > +
> > +    if (is_power_of_2(value)) {
> > +        return value;
> > +    }
> 
> please call clz64 after is_power_of_2.

All callers under clz64() are inline, so the optimizer can see that
there are no side effects and move the code if it would be faster;
I thought that separating it would only make the code uglier, because
QEMU doesn't allow lazy declarations ...

Markus had another design issue with this patch, so I'll send a v2 after
reaching the conclusion there.

Thanks.