From: David Daney <ddaney@caviumnetworks.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Fwd: [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG.
Date: Thu, 10 Sep 2009 17:31:19 -0700 [thread overview]
Message-ID: <4AA99A57.70804@caviumnetworks.com> (raw)
Drat, I forgot to CC linux-kernel with this message. Well in case you
missed it, here it is again.
-------- Original Message --------
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
From: David Daney <ddaney@caviumnetworks.com>
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(-)
reply other threads:[~2009-09-11 0:31 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4AA99A57.70804@caviumnetworks.com \
--to=ddaney@caviumnetworks.com \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.