[PATCH v3] hash: fix SSE comparison

[Bruce Richardson]

On Sat, Oct 07, 2023 at 03:36:34PM +0800, Jieqiang Wang wrote:
> __mm_cmpeq_epi16 returns 0xFFFF if the corresponding 16-bit elements are
> equal. In original SSE2 implementation for function compare_signatures,
> it utilizes _mm_movemask_epi8 to create mask from the MSB of each 8-bit
> element, while we should only care about the MSB of lower 8-bit in each
> 16-bit element.
> For example, if the comparison result is all equal, SSE2 path returns
> 0xFFFF while NEON and default scalar path return 0x5555.
> Although this bug is not causing any negative effects since the caller
> function solely examines the trailing zeros of each match mask, we
> recommend this fix to ensure consistency with NEON and default scalar
> code behaviors.
> 
> Fixes: c7d93df552c2 ("hash: use partial-key hashing")
> Cc: stable at dpdk.org
> 
> v2:
> 1. Utilize scalar mask instead of vector mask to save extra loads (Bruce)
> 
> v3:
> 1. Fix coding style warnings
> 
> Signed-off-by: Feifei Wang <feifei.wang2 at arm.com>
> Signed-off-by: Jieqiang Wang <jieqiang.wang at arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>

Acked-by: Bruce Richardson <bruce.richardson at intel.com>