start on SIMD documentation

[Peter Alexander]

On 13/01/12 8:39 AM, Walter Bright wrote:
> https://github.com/D-Programming-Language/d-programming-language.org/blob/master/simd.dd
>
>
> and core.simd:
>
> https://github.com/D-Programming-Language/druntime/blob/master/src/core/simd.d
>

Nice!

Although...

import core.simd;
void main()
{
     float4 a = void; // float a; doesn't work either
     a = simd(XMM.PXOR, a);
}

*** Internal error: backend/cgcod.c 2048 ***

Are all those instructions implemented? I seem to get the same for all 
instructions.

Also, slight bikeshedding issue: I'm not so sure on using names like 
int4 for vectors. You see things like int32 a lot to mean a 32-bit 
integer, or int8 to mean an 8-bit integer. Using this notation for 
vectors may be confusing.

As for what to change it to, I don't really care. int4v, vec_int4, 
int_vector4, anything. It doesn't matter.