Re: [PATCH v3] net: fix build error with clang

Interestingly, clang and gcc has different prototype for _mm_prefetch().
For gcc, we have

   _mm_prefetch (const void *__P, enum _mm_hint __I)

While for clang, it's

   #define _mm_prefetch(a, sel) (__builtin_prefetch((void *)(a), 0, (sel)))

That's how the following error comes with clang:

   error: cast from 'const void *' to 'void *' drops const qualifier
   [-Werror,-Wcast-qual]
           _mm_prefetch((const void *)rused, _MM_HINT_T0);
   /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include/xmmintrin.h:684:58:
   note: expanded from macro '_mm_prefetch'
            #define _mm_prefetch(a, sel) (__builtin_prefetch((void *)(a),
                                          0, (sel)))

What's weird is that the build was actaully Okay before. I met it while
apply Jerin's vector support for ARM patch set: he just move this peiece
of code to another file, nothing else changed.

This patch fix the issue when Jerin's patchset is applied. Thus, I think
it's still needed.

Similarly, make the same change to other _mm_prefetch users, just in case
this weird issue shows up again somehow later.

Fixes: fc3d66212fed ("virtio: add vector Rx")
Fixes: c95584dc2b18 ("ixgbe: new vectorized functions for Rx/Tx")
Fixes: 9ed94e5bb04e ("i40e: add vector Rx")
Fixes: 7092be8437bd ("fm10k: add vector Rx")

Cc: Jerin Jacob <redacted>
Cc: Chen Jing D(Mark) <redacted>
Cc: Cunming Liang <redacted>
Cc: Bruce Richardson <redacted>
CC: Thomas Monjalon <redacted>
Signed-off-by: Yuanhan Liu <redacted>
---
v3: make the similar replace to other PMD
---
 drivers/net/fm10k/fm10k_rxtx_vec.c      | 2 +-
 drivers/net/i40e/i40e_rxtx_vec.c        | 2 +-
 drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c  | 2 +-
 drivers/net/virtio/virtio_rxtx_simple.c | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/fm10k/fm10k_rxtx_vec.c b/drivers/net/fm10k/fm10k_rxtx_vec.c
index 9ea747e..6b78c0f 100644
--- a/drivers/net/fm10k/fm10k_rxtx_vec.c
+++ b/drivers/net/fm10k/fm10k_rxtx_vec.c

@@ -406,7 +406,7 @@ fm10k_recv_raw_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 	 */
 	rxdp = rxq->hw_ring + next_dd;
 
-	_mm_prefetch((const void *)rxdp, _MM_HINT_T0);
+	rte_prefetch0(rxdp);
 
 	/* See if we need to rearm the RX queue - gives the prefetch a bit
 	 * of time to act

diff --git a/drivers/net/i40e/i40e_rxtx_vec.c b/drivers/net/i40e/i40e_rxtx_vec.c
index 51fb282..a9ca515 100644
--- a/drivers/net/i40e/i40e_rxtx_vec.c
+++ b/drivers/net/i40e/i40e_rxtx_vec.c

@@ -224,7 +224,7 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 	 */
 	rxdp = rxq->rx_ring + rxq->rx_tail;
 
-	_mm_prefetch((const void *)rxdp, _MM_HINT_T0);
+	rte_prefetch0(rxdp);
 
 	/* See if we need to rearm the RX queue - gives the prefetch a bit
 	 * of time to act

diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
index 1c4fd7c..94dfbd6 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c

@@ -243,7 +243,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 	 */
 	rxdp = rxq->rx_ring + rxq->rx_tail;
 
-	_mm_prefetch((const void *)rxdp, _MM_HINT_T0);
+	rte_prefetch0(rxdp);
 
 	/* See if we need to rearm the RX queue - gives the prefetch a bit
 	 * of time to act

diff --git a/drivers/net/virtio/virtio_rxtx_simple.c b/drivers/net/virtio/virtio_rxtx_simple.c
index 6517aa8..d8dd17c 100644
--- a/drivers/net/virtio/virtio_rxtx_simple.c
+++ b/drivers/net/virtio/virtio_rxtx_simple.c

@@ -200,7 +200,7 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 	sw_ring  = &vq->sw_ring[desc_idx];
 	sw_ring_end = &vq->sw_ring[vq->vq_nentries];
 
-	_mm_prefetch((const void *)rused, _MM_HINT_T0);
+	rte_prefetch0(rused);
 
 	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
 		virtio_rxq_rearm_vec(rxvq);

-- 
1.9.0