netdev - Re: [PATCH] lib/checksum.c: optimize do

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Date:	Thu, 07 Jul 2011 04:29:25 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	abbotti@....co.uk
Cc:	netdev@...r.kernel.org, arnd@...db.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/checksum.c: optimize do_csum a bit

From: Ian Abbott <abbotti@....co.uk>
Date: Thu, 7 Jul 2011 12:18:49 +0100

> Reduce the number of variables modified by the loop in do_csum() by 1,
> which seems like a good idea.  On Nios II (a RISC CPU with 3-operand
> instruction set) it reduces the loop from 7 to 6 instructions, including
> the conditional branch.
> 
> Signed-off-by: Ian Abbott <abbotti@....co.uk>

I think you'll overshoot past the end of the buffer when there are
trailing bytes to handle.

The whole reason we need the count variable is to handle those
kinds of cases.
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