From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:55790) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLbeh-0003yT-Cy for qemu-devel@nongnu.org; Tue, 09 Oct 2012 11:23:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TLbed-0001NS-Bb for qemu-devel@nongnu.org; Tue, 09 Oct 2012 11:23:35 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:42577) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLbed-0001NI-1k for qemu-devel@nongnu.org; Tue, 09 Oct 2012 11:23:31 -0400 Received: by mail-pa0-f45.google.com with SMTP id fb10so5272473pad.4 for ; Tue, 09 Oct 2012 08:23:30 -0700 (PDT) Sender: Richard Henderson Message-ID: <5074416F.5010708@twiddle.net> Date: Tue, 09 Oct 2012 08:23:27 -0700 From: Richard Henderson MIME-Version: 1.0 References: <1349202750-16815-1-git-send-email-rth@twiddle.net> <1349202750-16815-2-git-send-email-rth@twiddle.net> <20121009151357.GB14078@ohm.aurel32.net> In-Reply-To: <20121009151357.GB14078@ohm.aurel32.net> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 01/10] tcg: Split out swap_commutative as a subroutine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Aurelien Jarno Cc: qemu-devel@nongnu.org On 10/09/2012 08:13 AM, Aurelien Jarno wrote: >> > It also prefers >> > >> > add r, r, c >> > over >> > add r, c, r >> > >> > when both inputs are known constants. This doesn't matter for true add, as >> > we will fully constant fold that. But it matters for a follow-on patch using >> > this routine for add2 which may not be fully foldable. ... > Does this sum += and -= actually generates better code than the previous > one? It's not something obvious to read (fortunately there is the > comment for helping), so if it doesn't bring any optimization, it's > better to keep the previous form. Yes. See the comment within the log above. r~