net/ixgbe: use intrinsics to count packet in NEON Rx

vPMD for aarch64 calculates the number of received packets using a loop.
Change to use NEON intrinsics for calculation. This saves CPU cycles
and has slightly better performance.

Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>

diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c
index 86fb3af..eeb8259 100644 (file)
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c
@@ -144,6 +144,7 @@ desc_to_olflags_v(uint8x16x2_t sterr_tmp1, uint8x16x2_t sterr_tmp2,
 
 #define IXGBE_VPMD_DESC_DD_MASK                0x01010101
 #define IXGBE_VPMD_DESC_EOP_MASK       0x02020202
+#define IXGBE_UINT8_BIT                        (CHAR_BIT * sizeof(uint8_t))
 
 static inline uint16_t
 _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
@@ -211,7 +212,6 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
                uint64x2_t mbp1, mbp2;
                uint8x16_t staterr;
                uint16x8_t tmp;
-               uint32_t var = 0;
                uint32_t stat;
 
                /* B.1 load 2 mbuf point */
@@ -256,7 +256,6 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 
                /* C.2 get 4 pkts staterr value  */
                staterr = vzipq_u8(sterr_tmp1.val[1], sterr_tmp2.val[1]).val[0];
-               stat = vgetq_lane_u32(vreinterpretq_u32_u8(staterr), 0);
 
                /* set ol_flags with vlan packet type */
                desc_to_olflags_v(sterr_tmp1, sterr_tmp2, staterr,
@@ -282,12 +281,20 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 
                /* C* extract and record EOP bit */
                if (split_packet) {
+                       stat = vgetq_lane_u32(vreinterpretq_u32_u8(staterr), 0);
                        /* and with mask to extract bits, flipping 1-0 */
                        *(int *)split_packet = ~stat & IXGBE_VPMD_DESC_EOP_MASK;
 
                        split_packet += RTE_IXGBE_DESCS_PER_LOOP;
                }
 
+               /* C.4 expand DD bit to saturate UINT8 */
+               staterr = vshlq_n_u8(staterr, IXGBE_UINT8_BIT - 1);
+               staterr = vreinterpretq_u8_s8
+                               (vshrq_n_s8(vreinterpretq_s8_u8(staterr),
+                                       IXGBE_UINT8_BIT - 1));
+               stat = ~vgetq_lane_u32(vreinterpretq_u32_u8(staterr), 0);
+
                rte_prefetch_non_temporal(rxdp + RTE_IXGBE_DESCS_PER_LOOP);
 
                /* D.3 copy final 1,2 data to rx_pkts */
@@ -296,18 +303,12 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
                vst1q_u8((uint8_t *)&rx_pkts[pos]->rx_descriptor_fields1,
                         pkt_mb1);
 
-               stat &= IXGBE_VPMD_DESC_DD_MASK;
-
-               /* C.4 calc avaialbe number of desc */
-               if (likely(stat != IXGBE_VPMD_DESC_DD_MASK)) {
-                       while (stat & 0x01) {
-                               ++var;
-                               stat = stat >> 8;
-                       }
-                       nb_pkts_recd += var;
-                       break;
-               } else {
+               /* C.5 calc available number of desc */
+               if (unlikely(stat == 0)) {
                        nb_pkts_recd += RTE_IXGBE_DESCS_PER_LOOP;
+               } else {
+                       nb_pkts_recd += __builtin_ctz(stat) / IXGBE_UINT8_BIT;
+                       break;
                }
        }