[PATCH v10 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/compare_signatures_arm_pvt.h | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/lib/hash/compare_signatures_arm_pvt.h 
b/lib/hash/compare_signatures_arm_pvt.h
index e83bae9912..1d5464c4ce 100644
--- a/lib/hash/compare_signatures_arm_pvt.h
+++ b/lib/hash/compare_signatures_arm_pvt.h
@@ -32,21 +32,21 @@ compare_signatures_dense(uint16_t *hitmask_buffer,
        switch (sig_cmp_fn) {
 #if RTE_HASH_BUCKET_ENTRIES <= 8
        case RTE_HASH_COMPARE_NEON: {
-               uint16x8_t vmat, vsig, x;
-               int16x8_t shift = {0, 1, 2, 3, 4, 5, 6, 7};
-               uint16_t low, high;
+               uint16x8_t vmat, hit1, hit2;
+               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_bucket_sigs));
-               x = vshlq_u16(vandq_u16(vmat, vdupq_n_u16(0x0001)), shift);
-               low = (uint16_t)(vaddvq_u16(x));
+               vmat = vceqq_u16(vsig, vld1q_u16(prim_bucket_sigs));
+               hit1 = vandq_u16(vmat, mask);
+
                /* Compare all signatures in the secondary bucket */
-               vmat = vceqq_u16(vsig, vld1q_u16((uint16_t const 
*)sec_bucket_sigs));
-               x = vshlq_u16(vandq_u16(vmat, vdupq_n_u16(0x0001)), shift);
-               high = (uint16_t)(vaddvq_u16(x));
-               *hitmask_buffer = low | high << RTE_HASH_BUCKET_ENTRIES;
+               vmat = vceqq_u16(vsig, vld1q_u16(sec_bucket_sigs));
+               hit2 = vandq_u16(vmat, mask);
 
+               hit2 = vshlq_n_u16(hit2, RTE_HASH_BUCKET_ENTRIES);
+               hit2 = vorrq_u16(hit1, hit2);
+               *hitmask_buffer = vaddvq_u16(hit2);
                }
                break;
 #endif
-- 
2.25.1