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 <[email protected]>
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(-)