Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756315AbZKSV1w (ORCPT ); Thu, 19 Nov 2009 16:27:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755505AbZKSV1v (ORCPT ); Thu, 19 Nov 2009 16:27:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:63227 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754568AbZKSV1t (ORCPT ); Thu, 19 Nov 2009 16:27:49 -0500 Message-ID: <4B05B7AD.20500@redhat.com> Date: Thu, 19 Nov 2009 14:25:01 -0700 From: Jeff Law User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.4pre) Gecko/20091014 Fedora/3.0-2.8.b4.fc11 Thunderbird/3.0b4 MIME-Version: 1.0 To: "H. Peter Anvin" CC: rostedt@goodmis.org, David Daney , Linus Torvalds , Andrew Haley , Richard Guenther , Thomas Gleixner , Ingo Molnar , LKML , Andrew Morton , Heiko Carstens , feng.tang@intel.com, Fr??d??ric Weisbecker , Peter Zijlstra , jakub@redhat.com, gcc@gcc.gnu.org Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions References: In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1173 Lines: 26 On 11/19/09 14:14, H. Peter Anvin wrote: > Hence a new unconstrained option... > Not arguing against it, just noting there are targets where after the prologue mcount is mandated. There's certainly hooks in GCC to do it both ways and if there's no clear need to use after-prologue on x86-linux, then before-prologue seems reasonable to me. It's also the case that aligning stacks on the x86 and the poor code generated when used with profiling is an interaction I doubt anyone has looked at until now. The result is definitely ugly and inefficient -- and there's something to be said for cleaning that up and at least marginally reducing the overhead of profiling. Having said all that, I don't expect to personally be looking at the problem, given the list of other codegen issues that need to be looked at (reload in particular), profiling/stack interactions would be around 87 millionth on my list. jeff -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/