start on SIMD documentation

[Walter Bright]

On 1/13/2012 11:06 AM, Peter Alexander wrote:
> 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.

The instructions are implemented, it's the initialization that isn't and is failing.


> 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.

If int4 is out, I'd prefer something like vint4. Something short.