From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 14 Sep 2009 23:51:36 +0200 (CEST) Received: from mail3.caviumnetworks.com ([12.108.191.235]:9324 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by ftp.linux-mips.org with ESMTP id S2097347AbZINVvV (ORCPT ); Mon, 14 Sep 2009 23:51:21 +0200 Received: from caexch01.caveonetworks.com (Not Verified[192.168.16.9]) by mail3.caviumnetworks.com with MailMarshal (v6,5,4,7535) id ; Mon, 14 Sep 2009 14:50:58 -0700 Received: from caexch01.caveonetworks.com ([192.168.16.9]) by caexch01.caveonetworks.com with Microsoft SMTPSVC(6.0.3790.3959); Mon, 14 Sep 2009 14:50:59 -0700 Received: from dd1.caveonetworks.com ([12.108.191.236]) by caexch01.caveonetworks.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.3959); Mon, 14 Sep 2009 14:50:59 -0700 Message-ID: <4AAEBAC2.1050905@caviumnetworks.com> Date: Mon, 14 Sep 2009 14:50:58 -0700 From: David Daney User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Linus Torvalds , Andrew Morton CC: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, ralf@linux-mips.org, linux-mips@linux-mips.org, Martin Schwidefsky , Heiko Carstens , linux390@de.ibm.com, linux-s390@vger.kernel.org, David Howells , Koichi Yasutake , linux-am33-list@redhat.com, Kyle McMartin , Helge Deller , linux-parisc@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@ozlabs.org, Richard Henderson , Ivan Kokshaysky , linux-alpha@vger.kernel.org, Haavard Skinnemoen , Mike Frysinger , uclinux-dist-devel@blackfin.uclinux.org, Linux Kernel Mailing List , linux-arch@vger.kernel.org, Roland McGrath Subject: [PATCH 00/11] Add support for GCC's __builtin_unreachable() and use it in BUG (v2). Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 14 Sep 2009 21:50:59.0414 (UTC) FILETIME=[72114F60:01CA3585] Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 24031 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ddaney@caviumnetworks.com Precedence: bulk X-list: linux-mips When I sent the first version, I had not realized that Roland McGrath had only a day or two earlier submitted a very similar patch (although one that only fixed up the x86 case). I have been working on this quite a while now, starting with adding the required support to GCC, so with an eye towards finishing it up I have this new version. From the announcement of the first version: Starting with version 4.5, GCC has a new built-in function called __builtin_unreachable(). The function tells the compiler that control flow will never reach that point. Currently we trick the compiler by putting in for(;;); but this has the disadvantage that extra code is emitted for an endless loop. For an i386 kernel using __builtin_unreachable() results in an defaultconfig that is nearly 4000 bytes smaller. This patch set adds support to compiler.h creating a new macro usable in the kernel called unreachable(). If the compiler lacks __builtin_unreachable(), it just expands to for(;;). The x86 and MIPS patches I actually tested with a GCC-4.5 snapshot. Lacking the ability to test the rest of the architectures, I just did what seemed right without even trying to compile the kernel. For version 2: I fixed a couple of checkpatch issues, and simplified the unreachable() macro for the pre-GCC-4.5 case (as suggested by Richard Henderson). Also several Acked-by: were added. New in this version (as suggested by Ingo Molnar) I added 11/11 which uses unreachable() in asm-generic/bug.h for !CONFIG_BUG case. This one may be a little controversial as it will end up making code slightly larger when !CONFIG_BUG and you are using a pre-GCC-4.5 compiler. I will reply with the 11 patches. David Daney (11): Add support for GCC-4.5's __builtin_unreachable() to compiler.h (v2) x86: Convert BUG() to use unreachable() MIPS: Convert BUG() to use unreachable() s390: Convert BUG() to use unreachable() mn10300: Convert BUG() to use unreachable() parisc: Convert BUG() to use unreachable() powerpc: Convert BUG() to use unreachable() alpha: Convert BUG() to use unreachable() avr32: Convert BUG() to use unreachable() blackfin: Convert BUG() to use unreachable() Use unreachable() in asm-generic/bug.h for !CONFIG_BUG case. arch/alpha/include/asm/bug.h | 3 ++- arch/avr32/include/asm/bug.h | 2 +- arch/blackfin/include/asm/bug.h | 2 +- arch/mips/include/asm/bug.h | 4 +--- arch/mn10300/include/asm/bug.h | 3 ++- arch/parisc/include/asm/bug.h | 4 ++-- arch/powerpc/include/asm/bug.h | 2 +- arch/s390/include/asm/bug.h | 2 +- arch/x86/include/asm/bug.h | 4 ++-- include/asm-generic/bug.h | 4 ++-- include/linux/compiler-gcc4.h | 14 ++++++++++++++ include/linux/compiler.h | 5 +++++ 12 files changed, 34 insertions(+), 15 deletions(-)