Support for gcc vector attributes, SIMD builtins

[Iain Buclaw]

== Quote from Mike Farnsworth (mike.farnsworth at gmail.com)'s article
> On 02/01/2011 10:38 AM, Iain Buclaw wrote:
> > I haven't given it much thought on how internal representation could be, but I'd
> > lean on using unions in D code for usage in the language. As its probably most
> > portable.
> >
> > For example, one of the older 'hello vectors' I know of:
> >
> > import std.c.stdio;
> >
> > pragma(set_attribute, __v4sf, vector_size(16));
> > typedef float __v4sf;
> >
> > union f4vector
> > {
> >     __v4sf v;
> >     float[4] f;
> > }
> >
> > int main()
> > {
> >     f4vector a, b, c;
> >
> >     a.f = [1, 2, 3, 4];
> >     b.f = [5, 6, 7, 8];
> >
> >     c.v = a.v + b.v;
> >     printf("%f, %f, %f, %f\n", c.f[0], c.f[1], c.f[2], c.f[3]);
> >
> >     return 0;
> > }
> I've been giving this a serious try, and while the above works, I can't
> get any __builtin_... functions to actually work.  I've added support
> for the VECTOR_TYPE tree code in gcc_type_to_d_type(tree) function (in
> d_builtins2.cc):
>         case VECTOR_TYPE:
>         {
>             tree baseType = TREE_TYPE(t);
>             d = gcc_type_to_d_type(baseType, printstuff);
>             if (d)
>                 return d;
>             break;
>         }
> This allows it to succeed in interpreting the SSE-related builtins in
> gcc_type_to_d_type(tree).  Note that all it does is grab the base vector
> element type and convert that to a D type so as not to confuse the
> frontend; this way it matches the typedef for __v4sf, so as long as we
> use the union we won't lose data before we can pass it to a builtin.

Try:
        case VECTOR_TYPE:
        {
            tree basetype = TYPE_DEBUG_REPRESENTATION_TYPE(t);
            assert(TREE_CODE(basetype) == RECORD_TYPE);
            basetype = TREE_TYPE(TYPE_FIELDS(basetype));
            d = gcc_type_to_d_type(basetype);
            if (d)
            {
                d->ctype = t;
                return d;
            }
            break;
        }

That makes them static arrays, so you needn't require a whacky union to use vector
functions.

  float[4] a = [1,2,3,4], b = [5,6,7,8], c;
  c = __builtin_ia32_addps(a,b);



Secondly, __builtin_ia32_addps requires SSE turned on. Compile with -msse


Regards