From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 00/10] Add support for GCC's __builtin_unreachable()
	and use it in BUG.
Date: Thu, 24 Sep 2009 13:37:13 +1000
Message-ID: <1253763433.7103.391.camel@pasglop>
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To: David Daney <ddaney@caviumnetworks.com>
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, Andrew Morton <akpm@linux-foundation.org>, Koichi Yasutake <yasutake.koichi@jp.panasonic.com>, Linus Torvalds <torvalds@linux-foundation.org>

On Thu, 2009-09-10 at 16:54 -0700, David Daney wrote:
> 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.

For the powerpc part:

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>