[dpdk-dev] [PATCH v2] net/virtio: fix build error with clang

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

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 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.

Fixes: fc3d66212fed ("virtio: add vector Rx")

Cc: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
v2: replace _mm_prefetch with rte_prefetch0 to make icc happy
---
 drivers/net/virtio/virtio_rxtx_simple.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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