Re: [Qemu-devel] [v3 1/3] cutils: add avx2 instruction optimization

[Li, Liang Z]

> On 12/09/2015 01:32 AM, Li, Liang Z wrote:
> > I think you means the ' __attribute__((target("avx2")))', I have tried this
> way, the issue here is:
> >   without the ' -mavx2' option for gcc, there are compiling error:
> > '__m256i undeclared', the __attribute__((target("avx2"))) can't solve this
> issue.  Any idea?
> 
> You're right that you can't use the normal __m256i, as it doesn't get 
> declared.
>   But you can define the same type within the function itself.
> 
> Which is a simple matter of
> 
>    typedef long long __m256i __attribute__((vector_size(32)));
> 
>  From there, you might as well rely on other gcc extensions to instead write
> 
>     __m256i tmp0 = p[i + 0] | p[i + 1];
> 
> rather than obfuscating the code with AVX2_VEC_OR.
> 
>
Comparing this way to  putting the related code to a separate file, I think the 
latter is more simple.

Thanks
Liang