From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Henderson Subject: Re: [Qemu-devel] [PATCH for-1.7] target-i386: Fix build by providing stub kvm_arch_get_supported_cpuid() Date: Wed, 13 Nov 2013 04:54:05 +1000 Message-ID: <5282794D.20108@twiddle.net> References: <5281580D.7060305@redhat.com> <52816422.8060002@redhat.com> <52821A62.2050001@redhat.com> <52822958.8060508@redhat.com> <20131112132337.GB2008@redhat.com> <528233DD.6020306@redhat.com> <20131112140935.GD2008@redhat.com> <528241E0.5060503@redhat.com> <52824766.2000507@redhat.com> <52825009.10506@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm-devel , Gleb Natapov , Patch Tracking , QEMU Developers , Andreas Tobler , Anthony Liguori , Paolo Bonzini To: Anthony Liguori , Peter Maydell Return-path: Received: from mail-yh0-f49.google.com ([209.85.213.49]:63872 "EHLO mail-yh0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753616Ab3KLSyW (ORCPT ); Tue, 12 Nov 2013 13:54:22 -0500 Received: by mail-yh0-f49.google.com with SMTP id a41so732816yho.8 for ; Tue, 12 Nov 2013 10:54:21 -0800 (PST) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 11/13/2013 03:04 AM, Anthony Liguori wrote: > On Tue, Nov 12, 2013 at 8:08 AM, Peter Maydell wrote: >> On 12 November 2013 15:58, Paolo Bonzini wrote: >>> I don't really see a reason why QEMU should give clang more weight than >>> Windows or Mac OS X. >> >> I'm not asking for more weight (and actually my main >> reason for caring about clang is exactly MacOSX). I'm >> just asking that when a bug is reported whose underlying >> cause is "we don't work on clang because we're relying on >> undocumented behaviour of gcc" with an attached patch that >> fixes this by not relying on the undocumented behaviour, >> that we apply the patch rather than saying "why do we >> care about clang"... > > QEMU has always been intimately tied to GCC. Heck, it all started as > a giant GCC hack relying on entirely undocumented behavior (dyngen's > disassembly of functions). > > There's nothing intrinsically bad about being tied to GCC. If you > were making argument that we could do it a different way and the > result would be as nice or nicer, then it wouldn't be a discussion. > > But if supporting clang means we have to remove useful things, then > it's always going to be an uphill battle. > > In this case, the whole discussion is a bit silly. Have you actually For what it's worth, I think BOTH of the patches that have been posted should be applied. That is, the patch that does (X || 1) -> (1 || X), and the patch that adds the stub. Frankly I'd have thought this was obvious and I'm a bit dismayed about how long this thread has continued. As far as GCC is concerned, we consider trivial dead code elimination like this to be a quality of implementation issue. We would never remove it, even from -O0. We can't guarantee how successful we can be, but that's what bug reports and regression tests are for. r~