Message-ID: <4B213627.5000007@caviumnetworks.com>
Date: Thu, 10 Dec 2009 09:55:51 -0800
From: David Daney <ddaney@caviumnetworks.com>
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To: Russell King - ARM Linux <linux@arm.linux.org.uk>
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	<u.kleine-koenig@pengutronix.de>,
       linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ARM: Convert BUG() to use unreachable()
References: <1260266138-17684-1-git-send-email-u.kleine-koenig@pengutronix.de> <20091210175007.GC13210@n2100.arm.linux.org.uk>
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Russell King - ARM Linux wrote:
> On Tue, Dec 08, 2009 at 10:55:38AM +0100, Uwe Kleine-K?nig wrote:
>> Use the new unreachable() macro instead of for(;;);
> 
> Have you investigated what effect this has on generated code?

Yes.

Pre GCC-4.5 the generated code should be identical as 'unreachable()' 
just expands to 'for(;;);' in this case.

Post GCC-4.5 the generated code should be smaller.

I have not tested on ARM, but on x86_64, i686, and mips64 this is the 
case.  The code size reduction is due to not emitting an endless loop 
after the asm() that never returns.

David Daney
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