From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Mzvro-0002UA-V9 for qemu-devel@nongnu.org; Mon, 19 Oct 2009 13:17:56 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Mzvrj-0002RQ-RY for qemu-devel@nongnu.org; Mon, 19 Oct 2009 13:17:56 -0400 Received: from [199.232.76.173] (port=43301 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Mzvrj-0002R8-MX for qemu-devel@nongnu.org; Mon, 19 Oct 2009 13:17:51 -0400 Received: from cantor2.suse.de ([195.135.220.15]:49926 helo=mx2.suse.de) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Mzvrj-0000Lk-B2 for qemu-devel@nongnu.org; Mon, 19 Oct 2009 13:17:51 -0400 From: Ulrich Hecht Subject: Re: [Qemu-devel] [PATCH 1/9] TCG "sync" op Date: Mon, 19 Oct 2009 19:17:55 +0200 References: <1255696735-21396-1-git-send-email-uli@suse.de> <20091016155221.GF4127@hall.aurel32.net> <20091017085904.GA9115@laped.iglesias.mooo.com> In-Reply-To: <20091017085904.GA9115@laped.iglesias.mooo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Message-Id: <200910191917.56502.uli@suse.de> Content-Transfer-Encoding: quoted-printable List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Edgar E. Iglesias" Cc: riku.voipio@iki.fi, qemu-devel@nongnu.org, aurelien@aurel32.net, agraf@suse.de On Saturday 17 October 2009, Edgar E. Iglesias wrote: > I looked at the s390 patches and was also unsure about this sync op. > I'm not convinced it's bad but my first feeling was as Aurelien points > out that the translator shoud take care of it. Indeed. I would have expected it to, in fact. But it doesn't. The sync op= =20 is the simplest and quickest way to get what I want that I could come up=20 with. I'd be perfectly happy if TCG could handle aliases on its own, but=20 doing a lot of ALU operations on every register access is not an option. > Another thing I noticed was the large amount of helpers. Without > looking at the details my feeling was that you could probably do more > at translation time. My experience is that helper functions have an undeservedly bad image. A=20 pure const helper call is very easy to optimize away for TCG. Random bit=20 shifting, comparing and branching isn't. > Nice work! Thank you. CU Uli --=20 SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG N=FCrnberg)