From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753119Ab0ETMpE (ORCPT ); Thu, 20 May 2010 08:45:04 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:36193 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752521Ab0ETMpA (ORCPT ); Thu, 20 May 2010 08:45:00 -0400 Date: Thu, 20 May 2010 14:44:53 +0200 From: Ingo Molnar To: "H. Peter Anvin" Cc: Mauro Carvalho Chehab , Eric Dumazet , mingo@redhat.com, linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com, tglx@linutronix.de, avi@redhat.com, linux-tip-commits@vger.kernel.org Subject: Re: Does anyone care about gcc 3.x support for x86 anymore? Message-ID: <20100520124453.GC2734@elte.hu> References: <1273135546-29690-2-git-send-email-avi@redhat.com> <1274213443.2485.3.camel@edumazet-laptop> <4BF2FF26.9050701@zytor.com> <1274217067.2485.9.camel@edumazet-laptop> <4BF308E9.4040809@zytor.com> <4BF46FFE.1080903@redhat.com> <4BF48569.7080203@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BF48569.7080203@zytor.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * H. Peter Anvin wrote: > On 05/19/2010 04:10 PM, Mauro Carvalho Chehab wrote: > > > > However, if the problems are just performance/dead > > code removal, I would just add a big warning if > > someone tries to compile x86 with it. I don't like > > very much the idea of having different minimum gcc > > requirements for each architecture, except if gcc is > > producing a broken code. > > > > I should clarify the problem. The problems we have seen > are related to constant propagation, which causes gcc3 > to die when there is an assembly constraint like: > > asm("..." : : "i" (foo)); > > ... since "foo" isn't constant as far as it is > concerned. We can put in workarounds, but it's real > effort to keep it alive that probably isn't well spent. > > Similarly, lack of constant propagation can cause code > that should have been compile-time removed to still be > there, causing link failures. Put in a deprecation warning first perhaps? Ingo