Re: AMD optimizations?

Oliver Xymoron (oxymoron@waste.org)
Thu, 26 Aug 1999 13:22:22 -0500 (CDT)


On Thu, 26 Aug 1999, Alan Cox wrote:

> > Likewise, has anyone worked on an MMX version of the TCP partial
> > checksum?
>
> I looked at it - its hard, very hard. MMX has no carry bit so you end up
> having to do a cycle of
>
> copy original 4 words
> add 4 new words
> for each new word < old word
> add one

As I pointed out a long time ago, you can do the whole thing 32-bits wide
and correct it at the end. No conditionals or carries required in the main
loop.

--
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.." 

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