From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MsBUQ-0003wF-Ph for qemu-devel@nongnu.org; Mon, 28 Sep 2009 04:21:46 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MsBUP-0003vO-VW for qemu-devel@nongnu.org; Mon, 28 Sep 2009 04:21:46 -0400 Received: from [199.232.76.173] (port=48561 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MsBUP-0003v9-Nr for qemu-devel@nongnu.org; Mon, 28 Sep 2009 04:21:45 -0400 Received: from fg-out-1718.google.com ([72.14.220.152]:15911) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MsBUP-0002DP-7x for qemu-devel@nongnu.org; Mon, 28 Sep 2009 04:21:45 -0400 Received: by fg-out-1718.google.com with SMTP id d23so1341645fga.10 for ; Mon, 28 Sep 2009 01:21:43 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4AC06AF0.7010300@redhat.com> References: <200909271613.n8RGDCLo020606@d01av04.pok.ibm.com> <4AC06AF0.7010300@redhat.com> Date: Mon, 28 Sep 2009 10:21:43 +0200 Message-ID: <761ea48b0909280121r13c14861y4a0a2683ffb79d2b@mail.gmail.com> Subject: Re: [Qemu-devel] Re: [Qemu-commits] [COMMIT a4b18c6] tcg/x86_64: generated dec/inc instead of sub/addwhen possible From: Laurent Desnogues Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: "qemu-devel@nongnu.org" , Aurelien Jarno On Mon, Sep 28, 2009 at 9:51 AM, Avi Kivity wrote: > On 09/27/2009 06:13 PM, Anthony Liguori wrote: >> >> From: Aurelien Jarno >> > > Intel recommends not using inc/dec. =A0Since these instructions don't upd= ate > all of the flags, they cannot be issued in parallel to previous instructi= ons > that do. That's true, but I think Icache misses will cost you more than the false dependencies; due to code size expansion in the translation process, optimizing rules should not be obeyed blindly. I guess this should be measured. Laurent