From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1ML2ao-0006l5-Hh for qemu-devel@nongnu.org; Sun, 28 Jun 2009 18:11:22 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1ML2ak-0006kp-2z for qemu-devel@nongnu.org; Sun, 28 Jun 2009 18:11:22 -0400 Received: from [199.232.76.173] (port=51334 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ML2aj-0006km-Ut for qemu-devel@nongnu.org; Sun, 28 Jun 2009 18:11:17 -0400 Received: from mail2.shareable.org ([80.68.89.115]:58647) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1ML2aj-0003KR-IF for qemu-devel@nongnu.org; Sun, 28 Jun 2009 18:11:17 -0400 Date: Sun, 28 Jun 2009 23:11:12 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] Re: [PATCH 08/11] QMP: Port balloon command Message-ID: <20090628221112.GC29896@shareable.org> References: <20090623135958.660903e1@doriath> <4A412135.2060804@us.ibm.com> <4A435F09.7050702@redhat.com> <20090625161143.01b56eea@doriath> <4A4492FD.4040704@redhat.com> <20090626094224.GE28206@redhat.com> <20090627125833.22d3cc9f@doriath> <4A4791D9.2050400@redhat.com> <5b31733c0906281023n637cd3eax60d14bbe618f63ec@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Blue Swirl Cc: Anthony Liguori , ehabkost@redhat.com, jan.kiszka@siemens.com, dlaor@redhat.com, qemu-devel@nongnu.org, Luiz Capitulino , Filip Navara , Avi Kivity Blue Swirl wrote: > On 6/28/09, Filip Navara wrote: > > On Sun, Jun 28, 2009 at 5:52 PM, Avi Kivity wrote: > > > It really isn't very complicated, and > > > the thread only got so long because the topic is relatively simple. Post an > > > RFC and a mile-long patchset about changing TCG to SSA form, and see how you > > > get no replies. > > > > > > I wouldn't even dare to push the SSA patch... Mile-long doesn't > > describe it precisely enough. Imagine it was applied to all the > > targets. > > Is there a speed benefit from using the SSA form? You can do some nice optimisations on SSA form, but you can do them without SSA too. It's just that SSA makes it easier to think about some things. SSA is only useful for interesting control flow graphs with many basic blocks, though. As far as I know, QEMU only translates code in linear instruction traces - so most SSA optimisations don't apply, and those which remain are easy to think about in any representation. -- Jamie