| From: |
| David Daney <ddaney@caviumnetworks.com> |
| To: |
| Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org> |
| Subject: |
| [PATCH 00/11] Add support for GCC's __builtin_unreachable() and use
it in BUG (v2). |
| Date: |
| Mon, 14 Sep 2009 14:50:58 -0700 |
| Message-ID: |
| <4AAEBAC2.1050905@caviumnetworks.com> |
| 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,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org, Roland McGrath <roland@redhat.com> |
| Archive‑link: | |
Article |
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(-)
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