Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753548AbbGASMh (ORCPT ); Wed, 1 Jul 2015 14:12:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39563 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752953AbbGASM2 (ORCPT ); Wed, 1 Jul 2015 14:12:28 -0400 Message-ID: <55942D8A.7060105@redhat.com> Date: Wed, 01 Jul 2015 14:12:26 -0400 From: Vladimir Makarov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Jakub Jelinek CC: Andy Lutomirski , gcc@gcc.gnu.org, "linux-kernel@vger.kernel.org" , Linus Torvalds , "H. Peter Anvin" , Ingo Molnar , Thomas Gleixner Subject: Re: gcc feature request / RFC: extra clobbered regs References: <20150630213736.GQ10247@tucnak.redhat.com> <559405E5.7000405@redhat.com> <20150701153133.GY10247@tucnak.redhat.com> <559424D4.6010908@redhat.com> <20150701174333.GA10247@tucnak.redhat.com> In-Reply-To: <20150701174333.GA10247@tucnak.redhat.com> Content-Type: text/plain; charset=windows-1252; 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: 1654 Lines: 34 On 07/01/2015 01:43 PM, Jakub Jelinek wrote: > On Wed, Jul 01, 2015 at 01:35:16PM -0400, Vladimir Makarov wrote: >> Actually it raise a question for me. If we describe that a function >> clobbers more than calling convention and then use it as a value (assigning >> a variable or passing as an argument) and loosing a track of it and than >> call it. How can RA know what the call clobbers actually. So for the >> function with the attributes we should prohibit use it as a value or make >> the attributes as a part of the function type, or at least say it is unsafe. >> So now I see this as a *bigger problem* with this extension. Although I >> guess it already exists as we have description of different ABI as an >> extension. > Unfortunately target attribute is function decl attribute rather than > function type. And having more attributes affect switchable targets will be > non-fun. > > Making attributes a part of type probably creates a lot issues too. Although I am not a front-end developer, still I think it is hard to implement in front-end. Sticking fully to this approach, it would be logical to describe this as a debug info (I am not sure it is even possible). Portability would be an issue too. It is hard to prevent for a regular C developer to assign such function to variable because it is ok on his system while the compilation of such code may fail on another system. -- 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/