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Date: Fri, 21 Nov 2014 06:22:42 -0500
From: Neil Horman <nhorman@tuxdriver.com>
To: Yerden Zhumabekov <e_zhumabekov@sts.kz>
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Subject: Re: [dpdk-dev] [PATCH v5 4/7] hash: add rte_hash_crc_8byte function
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On Thu, Nov 20, 2014 at 11:16:34AM +0600, Yerden Zhumabekov wrote:
> SSE4.2 provides CRC32 intrinsic with 8-byte operand.
> 
> Signed-off-by: Yerden Zhumabekov <e_zhumabekov@sts.kz>
> ---
>  lib/librte_hash/rte_hash_crc.h |   16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_hash_crc.h
> index cd28833..2c8ec99 100644
> --- a/lib/librte_hash/rte_hash_crc.h
> +++ b/lib/librte_hash/rte_hash_crc.h
> @@ -413,6 +413,22 @@ rte_hash_crc_4byte(uint32_t data, uint32_t init_val)
>  }
>  
>  /**
> + * Use single crc32 instruction to perform a hash on a 8 byte value.
> + *
> + * @param data
> + *   Data to perform hash on.
> + * @param init_val
> + *   Value to initialise hash generator.
> + * @return
> + *   32bit calculated hash value.
> + */
> +static inline uint32_t
> +rte_hash_crc_8byte(uint64_t data, uint32_t init_val)
> +{
> +	return crc32c_sse42_u64(data, init_val);
> +}
> +
> +/**
>   * Use crc32 instruction to perform a hash.
>   *
>   * @param data
> -- 
> 1.7.9.5
> 
> 

I'm sorry, it may be early here, so I may be missing something. The assembly
implementations look great, but if a user calls rte_hash_crc_8byte on a system
that doesn't support ss342, how do they wind up getting into the software crc
implementation given what you have above?
Neil