Re: [PATCH 2/3] x86/hash: swap parameters of crc32_u32()

[H. Peter Anvin]

On 02/24/2014 04:41 AM, Jan Beulich wrote:
> > So I'm guessing this hash is deliberately using the CRC32 instruction
> > "backwards", which would actually make sense: an actual CRC is actually
> > a pretty poor hash due to linearity.

OK, it really is even more confusing than that.

It does seem like the crc32 instruction really *is* commutative, which 
isn't something I would personally have expected at all.

Given that fact, I suspect the ordering in the DPDK is actually a bug, 
and that we should correct the ordering (which I would do at the call 
sites because it seems to make the code clearer) because it reduces the 
size of the loop by two instructions.

I guess I should find out how to file a bug report against DPDK too...

	-hpa

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