Re: [PATCH v2 0/2] dpdk: Allow for dynamic enablement of some isolated features

[Venky Venkatesan <venky.venkatesan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

Neil,

> Hey all-
>          I've been trying to update the fedora dpdk package to support VFIO
> enabled drivers and ran into a problem in which ixgbe didn't compile because the
> rxtx_vec code uses sse4.2 instruction intrinsics, which aren't supported in the
> default config I have.  I tried to remedy this by replacing the intrinsics with
> the __builtin macros, but it was pointed out (correctly), that this doesn't work
> properly.  So this is my second attempt, which I actually like a bit better.  I
> noted that code that uses intrinsics (ixgbe and the acl library), don't need to
> have those instructions turned on build-wide.  Rather, we can just enable the
> instructions in the specific code we want to build with support for that, and
> test for instruction support dynamically at run time.  This allows me to build
> the dpdk for a generic platform, but in such a way that some optimizations can
> be used if the executing cpu supports them at run time.
>
> Change notes:
>
> v2)
> 	* Added Log messages to run time check failures per Konstantin
> 	* Removed run time check caching in acl per Konstantin
>
> Signed-off-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
> CC: Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
>

One possible change to look at - the _mm_shuffle_epi8 is something that 
is available all the way from SSSE3, so you should be able to leave that 
in. The SSE4.2 dependency is only for the popcount (and 
__builtin_popcountll will work for that anyway). That should make things 
simpler.

-Venky