[dpdk-dev,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 <jerin.jacob@caviumnetworks.com>
Cc: Chen Jing D(Mark) <jing.d.chen@intel.com>
Cc: Cunming Liang <cunming.liang@intel.com>
Cc: Bruce Richardson <bruce.richardson@intel.com>
CC: Thomas Monjalon <thomas.monjalon@6wind.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
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(-)
  

Can any PMD guys review it? It blocks a virtio patchset apply...

Thanks.

	--yliu

On Mon, Sep 26, 2016 at 12:29:13PM +0800, Yuanhan Liu wrote:
> 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 <jerin.jacob@caviumnetworks.com>
> Cc: Chen Jing D(Mark) <jing.d.chen@intel.com>
> Cc: Cunming Liang <cunming.liang@intel.com>
> Cc: Bruce Richardson <bruce.richardson@intel.com>
> CC: Thomas Monjalon <thomas.monjalon@6wind.com>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
> 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
  

Hi, 

> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Tuesday, September 27, 2016 5:20 AM
> To: dev@dpdk.org
> Cc: Jerin Jacob <jerin.jacob@caviumnetworks.com>; Chen, Jing D
> <jing.d.chen@intel.com>; Liang, Cunming <cunming.liang@intel.com>;
> Richardson, Bruce <bruce.richardson@intel.com>; Thomas Monjalon
> <thomas.monjalon@6wind.com>
> Subject: Re: [PATCH v3] net: fix build error with clang
> 
> Can any PMD guys review it? It blocks a virtio patchset apply...
> 
> Thanks.
> 
> 	--yliu
> 
> On Mon, Sep 26, 2016 at 12:29:13PM +0800, Yuanhan Liu wrote:
> > 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 <jerin.jacob@caviumnetworks.com>
> > Cc: Chen Jing D(Mark) <jing.d.chen@intel.com>
> > Cc: Cunming Liang <cunming.liang@intel.com>
> > Cc: Bruce Richardson <bruce.richardson@intel.com>
> > CC: Thomas Monjalon <thomas.monjalon@6wind.com>
> > Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Acked-by: Jing Chen <jing.d.chen@intel.com>
  

On Tue, Sep 27, 2016 at 05:24:35PM +0000, Chen, Jing D wrote:
> > On Mon, Sep 26, 2016 at 12:29:13PM +0800, Yuanhan Liu wrote:
> > > 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.
...
> > > Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> Acked-by: Jing Chen <jing.d.chen@intel.com>

Mark, thank you!

Applied to dpdk-next-virtio.

	--yliu