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Date: Mon, 21 Dec 2009 20:12:00 -0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Richard Henderson <rth@redhat.com>
Cc: Richard Guenther <richard.guenther@gmail.com>, 	David Daney <ddaney@caviumnetworks.com>, 	"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>, 	Jamie Lokier <jamie@shareable.org>, linux-kernel@vger.kernel.org, 	linux-arm-kernel@lists.infradead.org, 	Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= <u.kleine-koenig@pengutronix.de>
Subject: Re: [PATCH] ARM: Convert BUG() to use unreachable()
Message-ID: <20091221201059.GD11669@n2100.arm.linux.org.uk>
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On Mon, Dec 21, 2009 at 11:30:43AM -0800, Richard Henderson wrote:
> On 12/17/2009 10:17 AM, Russell King - ARM Linux wrote:
>> How is "size-optimal trap" defined?
>
> E.g. Sparc and MIPS have "tcc" instructions that trap based on the
> condition codes, and so we eliminate the branch.  That's the only
> optimization we apply with __builtin_trap.
>
>> Let me put it another way: I want this function to terminate with an
>> explicit NULL pointer dereference in every case.
>
> Then just use that.

That's precisely what we have been using for many years.