From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28636 invoked by alias); 24 Oct 2007 20:42:45 -0000 Received: (qmail 28621 invoked by uid 22791); 24 Oct 2007 20:42:44 -0000 X-Spam-Check-By: sourceware.org Received: from NaN.false.org (HELO nan.false.org) (208.75.86.248) by sourceware.org (qpsmtpd/0.31) with ESMTP; Wed, 24 Oct 2007 20:42:42 +0000 Received: from nan.false.org (localhost [127.0.0.1]) by nan.false.org (Postfix) with ESMTP id 5556F98344; Wed, 24 Oct 2007 20:42:40 +0000 (GMT) Received: from caradoc.them.org (22.svnf5.xdsl.nauticom.net [209.195.183.55]) by nan.false.org (Postfix) with ESMTP id 39E21981F2; Wed, 24 Oct 2007 20:42:40 +0000 (GMT) Received: from drow by caradoc.them.org with local (Exim 4.68) (envelope-from ) id 1Ikn3n-0005j7-5j; Wed, 24 Oct 2007 16:42:39 -0400 Date: Wed, 24 Oct 2007 20:47:00 -0000 From: Daniel Jacobowitz To: Ulrich Weigand Cc: gdb-patches@sourceware.org Subject: Re: [commit] Use -mabi=altivec for AltiVec tests Message-ID: <20071024204239.GO10943@caradoc.them.org> Mail-Followup-To: Ulrich Weigand , gdb-patches@sourceware.org References: <20071021130504.GA10828@caradoc.them.org> <200710211807.l9LI7vCL011126@d12av02.megacenter.de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200710211807.l9LI7vCL011126@d12av02.megacenter.de.ibm.com> User-Agent: Mutt/1.5.15 (2007-04-09) X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2007-10/txt/msg00625.txt.bz2 On Sun, Oct 21, 2007 at 08:07:57PM +0200, Ulrich Weigand wrote: > Sorry, I didn't consider this controversial, or I would have posted an RFC > first ... I understand it to be general practice to use -mabi=altivec > with applications on Linux, and that should be OK as long as no system > library interface using vector arguments is used. Is this a problem > in other environments? > > However, if you prefer, I certainly have no objections to reverting the > patch (or maybe restricting it to Linux only) ... My understanding (courtesy of Geoff Keating) is that on most PowerPC targets this only affects the passing of vector registers. On some (powerpc-eabi; I am not sure if there are others, but I do not know of any) it increases the required stack alignment. If your CRT files don't do this, then saving the vector registers may do bad things to your stack frame. I know my local GDB works both with -mabi=altivec and without it, because I run this test in two multilibs :-) For now, what do you think we should do about the option? Restrict it to Linux? > > Unfortunately the linker patch is hung up right now because it notices > > this same dubious action (linking -mabi=altivec and -mabi=no-altivec > > code) and warns about it. That causes a bunch of GCC testcase > > failures. The GCC testcases in question use, but do not actually > > need, -mabi=altivec; they just need a nasty bug in -maltivec > > -mabi=no-altivec fixed and my patch for that didn't get any comments > > :-( > > Can you point me to the patch in question? Maybe I can ping David ... http://gcc.gnu.org/ml/gcc-patches/2007-08/msg00438.html Perhaps I should ping that now that the .gnu_attribute bit went in separately. Actually, no, the patch predated my improved understanding of the stack alignment magic. It might be right for powerpc-eabi, but powerpc-linux actually does have a sufficiently aligned stack so it ought to save them properly. -- Daniel Jacobowitz CodeSourcery