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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH 19/60] microblaze_v4: checksum support
Date: Sun, 29 Jun 2008 00:28:14 +0200
To: monstr@seznam.cz
Cc: linux-arch@vger.kernel.org, Michal Simek <monstr@monstr.eu>,
	vapier.adi@gmail.com, arnd@arndb.de, matthew@wil.cx,
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> +static inline unsigned int
> +csum_tcpudp_nofold(unsigned long saddr, unsigned long daddr, unsigned 
> short len,
> +		unsigned short proto, unsigned int sum)
> +{
> +	__asm__("add %0, %4, %1\n\t"
> +		"addc %0, %4, %2\n\t"
> +		"addc %0, %4, %3\n\t"
> +		"addc %0, %4, r0\n\t"
> +		: "=d" (sum)
> +		: "d" (saddr), "d" (daddr), "d" (len + proto),
> +		"0"(sum));

"sum" should use an earlyclobber, i.e.  "=&d"(sum)  , since some
inputs are used after %0 is first written to.

Also, you can use "+" instead of "=" to say the argument is both
input and output, and get rid of %4, if you like.


Segher