From: David Daney <ddaney@caviumnetworks.com> To: Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org, ralf@linux-mips.org, linux-mips@linux-mips.org, Martin Schwidefsky <schwidefsky@de.ibm.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, linux390@de.ibm.com, linux-s390@vger.kernel.org, David Howells <dhowells@redhat.com>, Koichi Yasutake <yasutake.koichi@jp.panasonic.com>, linux-am33-list@redhat.com, Kyle McMartin <kyle@mcmartin.ca>, Helge Deller <deller@gmx.de>, linux-parisc@vger.kernel.org, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, linuxppc-dev@ozlabs.org, Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, linux-alpha@vger.kernel.org, Haavard Skinnemoen <hskinnemoen@atmel.com>, Mike Frysinger <vapier@gentoo.org>, uclinux-dist-devel@blackfin.uclinux.org Subject: [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG. Date: Thu, 10 Sep 2009 16:54:41 -0700 [thread overview] Message-ID: <4AA991C1.1050800@caviumnetworks.com> (raw) 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 allyesconfig 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. 01/10 adds the compiler.h support, the rest of the patches retrofit the various architecture BUG macros to use it instead of for(;;) or while(1) loops. I will reply with the 10 patches. The architecture specific patches I will send to a smaller set of people. David Daney (10): Add support for GCC-4.5's __builtin_unreachable() to compiler.h 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() arch/alpha/include/asm/bug.h | 2 +- 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/linux/compiler-gcc4.h | 14 ++++++++++++++ include/linux/compiler.h | 5 +++++ 11 files changed, 31 insertions(+), 13 deletions(-)
WARNING: multiple messages have this Message-ID (diff)
From: David Daney <ddaney@caviumnetworks.com> To: Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org> Cc: linux-mips@linux-mips.org, Heiko Carstens <heiko.carstens@de.ibm.com>, linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>, "H. Peter Anvin" <hpa@zytor.com>, linux-s390@vger.kernel.org, linux-am33-list@redhat.com, Helge Deller <deller@gmx.de>, x86@kernel.org, Ingo Molnar <mingo@redhat.com>, Mike Frysinger <vapier@gentoo.org>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, uclinux-dist-devel@blackfin.uclinux.org, Thomas Gleixner <tglx@linutronix.de>, Richard Henderson <rth@twiddle.net>, Haavard Skinnemoen <hskinnemoen@atmel.com>, linux-parisc@vger.kernel.org, ralf@linux-mips.org, Kyle McMartin <kyle@mcmartin.ca>, linux-alpha@vger.kernel.org, Martin Schwidefsky <schwidefsky@de.ibm.com>, linux390@de.ibm.com, Koichi Yasutake <yasutake.koichi@jp.panasonic.com> Subject: [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG. Date: Thu, 10 Sep 2009 16:54:41 -0700 [thread overview] Message-ID: <4AA991C1.1050800@caviumnetworks.com> (raw) 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 allyesconfig 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. 01/10 adds the compiler.h support, the rest of the patches retrofit the various architecture BUG macros to use it instead of for(;;) or while(1) loops. I will reply with the 10 patches. The architecture specific patches I will send to a smaller set of people. David Daney (10): Add support for GCC-4.5's __builtin_unreachable() to compiler.h 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() arch/alpha/include/asm/bug.h | 2 +- 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/linux/compiler-gcc4.h | 14 ++++++++++++++ include/linux/compiler.h | 5 +++++ 11 files changed, 31 insertions(+), 13 deletions(-)
next reply other threads:[~2009-09-10 23:54 UTC|newest] Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-09-10 23:54 David Daney [this message] 2009-09-10 23:54 ` [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG David Daney 2009-09-10 23:56 ` [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h David Daney 2009-09-10 23:56 ` David Daney 2009-09-10 23:56 ` David Daney 2009-09-10 23:56 ` David Daney 2009-09-11 0:14 ` Richard Henderson 2009-09-11 0:14 ` Richard Henderson 2009-09-11 0:14 ` Richard Henderson 2009-09-11 14:32 ` Michael Buesch 2009-09-11 14:32 ` Michael Buesch 2009-09-11 14:32 ` Michael Buesch 2009-09-11 15:58 ` David Daney 2009-09-11 15:58 ` David Daney 2009-09-11 15:58 ` David Daney 2009-09-11 15:58 ` David Daney 2009-09-12 7:22 ` Geert Uytterhoeven 2009-09-12 7:22 ` Geert Uytterhoeven 2009-09-12 7:22 ` Geert Uytterhoeven 2009-09-12 7:22 ` Geert Uytterhoeven 2009-09-12 7:22 ` Geert Uytterhoeven 2009-09-12 7:22 ` Geert Uytterhoeven 2009-09-14 15:40 ` David Daney 2009-09-14 15:40 ` David Daney 2009-09-14 15:40 ` David Daney 2009-09-14 15:40 ` David Daney 2009-09-10 23:56 ` [PATCH 02/10] x86: Convert BUG() to use unreachable() David Daney 2009-09-11 0:56 ` H. Peter Anvin 2009-09-11 1:09 ` Roland McGrath 2009-09-11 1:13 ` Linus Torvalds 2009-09-11 1:33 ` H. Peter Anvin 2009-09-11 1:37 ` Roland McGrath 2009-09-11 1:42 ` H. Peter Anvin 2009-09-11 6:07 ` Ingo Molnar 2009-09-11 15:55 ` David Daney 2009-09-13 20:12 ` H. Peter Anvin 2009-09-10 23:56 ` [PATCH 03/10] MIPS: " David Daney 2009-09-10 23:56 ` [PATCH 04/10] s390: " David Daney 2009-09-11 12:18 ` Martin Schwidefsky 2009-09-11 12:18 ` Martin Schwidefsky 2009-09-10 23:56 ` [PATCH 05/10] mn10300: " David Daney 2009-09-10 23:56 ` [PATCH 06/10] parisc: " David Daney 2009-09-28 3:20 ` Kyle McMartin 2009-09-10 23:56 ` [PATCH 07/10] powerpc: " David Daney 2009-09-10 23:56 ` David Daney 2009-09-10 23:56 ` [PATCH 08/10] alpha: " David Daney 2009-09-10 23:56 ` [PATCH 09/10] avr32: " David Daney 2009-09-11 7:31 ` Haavard Skinnemoen 2009-09-10 23:56 ` [PATCH 10/10] blackfin: " David Daney 2009-09-24 3:37 ` [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG Benjamin Herrenschmidt
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