From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:49544) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TIl1M-0003YE-KK for qemu-devel@nongnu.org; Mon, 01 Oct 2012 14:47:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TIl1G-0004oc-0P for qemu-devel@nongnu.org; Mon, 01 Oct 2012 14:47:12 -0400 Received: from mail-pb0-f45.google.com ([209.85.160.45]:45905) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TIl1F-0004oY-PF for qemu-devel@nongnu.org; Mon, 01 Oct 2012 14:47:05 -0400 Received: by pbbrp2 with SMTP id rp2so8103039pbb.4 for ; Mon, 01 Oct 2012 11:47:04 -0700 (PDT) Sender: Richard Henderson Message-ID: <5069E533.2030307@twiddle.net> Date: Mon, 01 Oct 2012 11:47:15 -0700 From: Richard Henderson MIME-Version: 1.0 References: <1348766397-20731-1-git-send-email-rth@twiddle.net> <1348766397-20731-5-git-send-email-rth@twiddle.net> <20121001184356.GB4623@ohm.aurel32.net> In-Reply-To: <20121001184356.GB4623@ohm.aurel32.net> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/7] tcg: Optimize double-word comparisons against zero List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Aurelien Jarno Cc: qemu-devel@nongnu.org On 2012-10-01 11:43, Aurelien Jarno wrote: > While it's a nice optimization to have, one that seems to happen a lot > more often is the two high parts being equal. It happens when the guest > is working on (u)int32_t. It depends on what target you're looking at. For alpha guest, all branches are comparisons vs zero, so LT/GE happens with some regularity. r~