[dpdk-dev] [PATCH v2 2/2] net/i40e: restrict pointer aliasing for NEON vPMD

[Gavin Hu <gavin.hu@arm.com>]

restrict pointer aliasing to optimize the code generated.

The patch showed ~3% performnace uplift on Arm N1SDP platform, and no
degradation on ThunderX2. The tet case is RFC2544 zero-loss L2
forwarding running testpmd.

[1] https://gcc.gnu.org/onlinedocs/gcc-4.8.5/gcc/Restricted-Pointers.html

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
---
 drivers/net/i40e/i40e_rxtx_vec_neon.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/net/i40e/i40e_rxtx_vec_neon.c b/drivers/net/i40e/i40e_rxtx_vec_neon.c
index 4376d8911..405bd82df 100644
--- a/drivers/net/i40e/i40e_rxtx_vec_neon.c
+++ b/drivers/net/i40e/i40e_rxtx_vec_neon.c
@@ -172,8 +172,8 @@ desc_to_olflags_v(struct i40e_rx_queue *rxq, uint64x2_t descs[4],
 #define I40E_UINT16_BIT (CHAR_BIT * sizeof(uint16_t))
 
 static inline void
-desc_to_ptype_v(uint64x2_t descs[4], struct rte_mbuf **rx_pkts,
-		uint32_t *ptype_tbl)
+desc_to_ptype_v(uint64x2_t descs[4], struct rte_mbuf **restrict rx_pkts,
+		uint32_t *restrict ptype_tbl)
 {
 	int i;
 	uint8_t ptype;
@@ -194,8 +194,8 @@ desc_to_ptype_v(uint64x2_t descs[4], struct rte_mbuf **rx_pkts,
  *   numbers of DD bits
  */
 static inline uint16_t
-_recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts,
-		   uint16_t nb_pkts, uint8_t *split_packet)
+_recv_raw_pkts_vec(struct i40e_rx_queue *restrict rxq, struct rte_mbuf
+	**restrict rx_pkts, uint16_t nb_pkts, uint8_t *split_packet)
 {
 	volatile union i40e_rx_desc *rxdp;
 	struct i40e_rx_entry *sw_ring;
@@ -432,7 +432,7 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts,
  *   numbers of DD bits
  */
 uint16_t
-i40e_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
+i40e_recv_pkts_vec(void *restrict rx_queue, struct rte_mbuf **restrict rx_pkts,
 		   uint16_t nb_pkts)
 {
 	return _recv_raw_pkts_vec(rx_queue, rx_pkts, nb_pkts, NULL);
@@ -494,8 +494,8 @@ vtx1(volatile struct i40e_tx_desc *txdp,
 }
 
 static inline void
-vtx(volatile struct i40e_tx_desc *txdp,
-		struct rte_mbuf **pkt, uint16_t nb_pkts,  uint64_t flags)
+vtx(volatile struct i40e_tx_desc *txdp, struct rte_mbuf **pkt,
+		uint16_t nb_pkts,  uint64_t flags)
 {
 	int i;
 
@@ -504,8 +504,8 @@ vtx(volatile struct i40e_tx_desc *txdp,
 }
 
 uint16_t
-i40e_xmit_fixed_burst_vec(void *tx_queue, struct rte_mbuf **tx_pkts,
-			  uint16_t nb_pkts)
+i40e_xmit_fixed_burst_vec(void *restrict tx_queue,
+	struct rte_mbuf **restrict tx_pkts, uint16_t nb_pkts)
 {
 	struct i40e_tx_queue *txq = (struct i40e_tx_queue *)tx_queue;
 	volatile struct i40e_tx_desc *txdp;
-- 
2.17.1