Re: [PATCH v3 2/4] virtio: move SSE based Rx implementation to separate file

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

On Fri, Aug 19, 2016 at 08:54:00AM +0530, Jerin Jacob wrote:
> On Thu, Aug 18, 2016 at 02:52:31PM +0800, Yuanhan Liu wrote:
> > On Tue, Jul 05, 2016 at 06:19:24PM +0530, Jerin Jacob wrote:
> > > Split out SSE instruction based virtio simple Rx
> > > implementation to a separate file
> > > 
> > > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > 
> > Hi,
> > 
> > I was about to apply this set. I then did some build test and found a
> > weird issue: it breaks the build with clang (ubuntu 16.04).
> > 
> >     drivers/net/virtio/virtio_rxtx_simple_sse.c:130:2: 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)))
> >                                                          ^
> >     1 error generated.
> > 
> > Weird enough I don't see this issue before this commit: the error
> > line is exactly the same before and after this commit.
> 
> Yes, I looked at the pre processed output as well, it comes as same before and
> after this commit.
> 
> > 
> > Another note is that _mm_prefetch() is actually with different prototype
> > for gcc and clang. For gcc, we have:
> > 
> >     _mm_prefetch (const void *__P, enum _mm_hint __I)
> > 
> > Any thoughts?
> 
> How about replacing "_mm_prefetch((const void *)rused, _MM_HINT_T0)"
> with "rte_prefetch0(rused)" to have same prototype and fix the issue
> with clang?

Yes, it should work. BTW, I have just sent out a patch for that. I will
apply yours when that patch has been applied.

	--yliu