Re: AMD optimizations?

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 26 Aug 1999 17:29:24 +0100 (BST)


> 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

and at the end you have add the pairs. Im not sure if Ingo played with this
a while ago.

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