From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14940 invoked by alias); 3 Aug 2010 09:38:00 -0000 Received: (qmail 14930 invoked by uid 22791); 3 Aug 2010 09:37:59 -0000 X-SWARE-Spam-Status: No, hits=-5.5 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,SPF_HELO_PASS,TW_ZJ,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 03 Aug 2010 09:37:55 +0000 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o739braE000663 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 3 Aug 2010 05:37:53 -0400 Received: from zebedee.pink (ovpn-113-87.phx2.redhat.com [10.3.113.87]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o739bpB7032012; Tue, 3 Aug 2010 05:37:52 -0400 Message-ID: <4C57E36F.2060703@redhat.com> Date: Tue, 03 Aug 2010 09:38:00 -0000 From: Andrew Haley User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0 MIME-Version: 1.0 To: gcc-patches@gcc.gnu.org Subject: Re: PATCH: Turn on -fomit-frame-pointer by default for 32bit Linux/x86 References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org X-SW-Source: 2010-08/txt/msg00173.txt.bz2 On 08/03/2010 10:18 AM, Uros Bizjak wrote: > On Mon, Aug 2, 2010 at 7:54 PM, H.J. Lu wrote: > >>> Here are the updated patch and spread sheet for SPEC CPU 2000/2006 on >>> Intel Core i7 which shows that -fomit-frame-pointer -fasynchronous-unwind-tables >>> improves performance by up to 12% at -O2 and 8% at -O3. For -Os, it improves >>> performance by up to 20%, but also increases code by up to 36%. >>> >>> This patch turns on -fomit-frame-pointer -fasynchronous-unwind-tables only if >>> -Os isn't used. >>> >>> Tested on Linux/ia32 and Linux/x86-64 with -m32. OK for trunk? >> >> Any comments on this patch. Any objections? > > IMO, this should be approved by Release Managers, since this decision > affects distributions and their users. > > I have no _technical_ objections to this patch, but I won't approve it > either due to the reason above. It's hard for us to know all the use cases that this patch will break: there may be many users who unwind the stack by following the call chain, a technique that has worked for many years. (And was even sanctioned by the ABI, wasn't it?) We'll know when if push this patch out and hear the screams. Is this really the right thing to do at this stage in the lifetime of legacy x86? Andrew.