[PATCH v5 2/4] hash: optimize compare signature for NEON

[Yoan Picchi]

Upon a successful comparison, NEON sets all the bits in the lane to 1
We can skip shifting by simply masking with specific masks.

Signed-off-by: Yoan Picchi <yoan.pic...@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
Reviewed-by: Nathan Brown <nathan.br...@arm.com>
---
 lib/hash/rte_cuckoo_hash.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
index 0550165584..a07dd3a28d 100644
--- a/lib/hash/rte_cuckoo_hash.c
+++ b/lib/hash/rte_cuckoo_hash.c
@@ -1871,19 +1871,17 @@ compare_signatures_dense(uint32_t *prim_hash_matches, 
uint32_t *sec_hash_matches
        /* For match mask every bits indicates the match */
        switch (sig_cmp_fn) {
        case RTE_HASH_COMPARE_NEON: {
-               uint16x8_t vmat, vsig, x;
-               int16x8_t shift = {0, 1, 2, 3, 4, 5, 6, 7};
+               uint16x8_t vmat, x;
+               const uint16x8_t mask = {0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 
0x80};
+               const uint16x8_t vsig = vld1q_dup_u16((uint16_t const *)&sig);
 
-               vsig = vld1q_dup_u16((uint16_t const *)&sig);
                /* Compare all signatures in the primary bucket */
-               vmat = vceqq_u16(vsig,
-                       vld1q_u16((uint16_t const *)prim_bkt->sig_current));
-               x = vshlq_u16(vandq_u16(vmat, vdupq_n_u16(0x0001)), shift);
+               vmat = vceqq_u16(vsig, vld1q_u16((uint16_t const 
*)prim_bkt->sig_current));
+               x = vandq_u16(vmat, mask);
                *prim_hash_matches = (uint32_t)(vaddvq_u16(x));
                /* Compare all signatures in the secondary bucket */
-               vmat = vceqq_u16(vsig,
-                       vld1q_u16((uint16_t const *)sec_bkt->sig_current));
-               x = vshlq_u16(vandq_u16(vmat, vdupq_n_u16(0x0001)), shift);
+               vmat = vceqq_u16(vsig, vld1q_u16((uint16_t const 
*)sec_bkt->sig_current));
+               x = vandq_u16(vmat, mask);
                *sec_hash_matches = (uint32_t)(vaddvq_u16(x));
                }
                break;
-- 
2.34.1