From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31372 invoked by alias); 27 Jun 2006 14:21:52 -0000 Received: (qmail 31330 invoked by uid 22791); 27 Jun 2006 14:21:51 -0000 X-Spam-Check-By: sourceware.org Received: from mx.laposte.net (HELO mx.laposte.net) (81.255.54.11) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 27 Jun 2006 14:21:47 +0000 Received: from smtp.laposte.net (10.150.9.35) by mx.laposte.net (7.2.060.1) id 449AA034004CCA14; Tue, 27 Jun 2006 16:21:09 +0200 Received: from laposte.net (10.150.9.86) by smtp.laposte.net (7.3.105.2) id 0000000000606F99; Tue, 27 Jun 2006 16:21:09 +0200 Date: Tue, 27 Jun 2006 14:21:00 -0000 Message-Id: Subject: Re: question about gcc assembly MIME-Version: 1.0 X-Sensitivity: 3 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable From: "Coline Lelong-Pantel" To: "tprince" Cc: "gcc-help" X-XaM3-API-Version: 4.1 (B103) X-SenderIP: 127.0.0.1 X-IsSubscribed: yes Mailing-List: contact gcc-help-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-help-owner@gcc.gnu.org X-SW-Source: 2006-06/txt/msg00235.txt.bz2 > Both gcc versions you quote are fairly old; if efficiency interests you, > you might try a current version. Were you able to show a significant > difference in performance on a CPU which is important to you? I have not checked that, my goal is to produce, if it is possible, the same assembly code. I would > guess the most important reason for avoiding use of eax here would be to > keep that register available for other use. The optimization could be > affected by compiler switches (-Os, -O2) or by selection of -march > option, and many other possibilities. If I try using optimisation flags or -march, i get a completely different code. > Newer CPUs have hardware merging of operations, as well as stalls on > certain immediate data operations, so it is impossible to know the > performance implications from what you have presented. What do you mean by "hardware merging of operations" ? Acc=E9dez au courrier =E9lectronique de La Poste : www.laposte.net 3615 LAPOSTENET (0,34 =80/mn)