From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16850 invoked by alias); 16 Mar 2010 16:04:31 -0000 Received: (qmail 16817 invoked by uid 22791); 16 Mar 2010 16:04:31 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,SARE_MSGID_LONG40 X-Spam-Check-By: sourceware.org Received: from mail-fx0-f211.google.com (HELO mail-fx0-f211.google.com) (209.85.220.211) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 16 Mar 2010 16:04:26 +0000 Received: by fxm3 with SMTP id 3so98124fxm.16 for ; Tue, 16 Mar 2010 09:04:24 -0700 (PDT) MIME-Version: 1.0 Received: by 10.239.188.139 with SMTP id p11mr1078693hbh.102.1268755464255; Tue, 16 Mar 2010 09:04:24 -0700 (PDT) In-Reply-To: References: <6dc9ffc81003160750ge5ec0a3l8cda117216bbb102@mail.gmail.com> <170A1D5F-CF9E-405F-9056-3D23FBE9F130@adacore.com> <87a8dc11003160837u14c2fdfenef62c73c851344ce@mail.gmail.com> From: Alexey Salmin Date: Tue, 16 Mar 2010 16:08:00 -0000 Message-ID: <87a8dc11003160904p678114cbj9522a62613f184f9@mail.gmail.com> Subject: Re: (un)aligned accesses on x86 platform. To: Tristan Gingold Cc: "H.J. Lu" , =?ISO-8859-2?Q?Pawe=B3_Sikora?= , gcc@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2010-03/txt/msg00185.txt.bz2 On Tue, Mar 16, 2010 at 9:48 PM, Tristan Gingold wrot= e: > > On Mar 16, 2010, at 4:37 PM, Alexey Salmin wrote: >>>> I am interested in an -mstrict-alignment option for x86. >>> >>> Not sure it will be useful. =A0The libc still does unaligned accesses I= IRC. >>> >> >> Wow. What for? > > Well, simply because it is not compiled with strict alignment. =A0There m= ight also be some optimization in > memory operation that does unaligned accesses. I always thought that unaligned access is much slower than aligned one. You mean code-size optimizations? Alexey