Comment by a1369209993

I think what you're looking for is ISPC.[0][1] It distinguishes between 'uniform' (scalar) vs 'varying' (vector) variables[2] and applies SIMD instructions pretty much transparently. It defaults to varying, whereas I think for a general-purpose C-like compiler you'd want scalar by default and explicitly declare eg:

  vector float add2(float base,vector float offs)
    {
    return base + 2*offs;
    }
  double sum(double* ar,size_t ln)
    {
    vector double x = (vector)0.0;
    while(ln >= sizeof vector) /* == # of simd lanes */
      {
      x += *ar; /* maybe this needs some kind of cast? */
      ln -= sizeof vector; /* == 1 on arches with no simd support */
      }
    /* this part's definitely not done properly */
    double buf[sizeof vector]; *buf = x;
    double ret = 0.0; /* slurp up the last few */
    for(size_t i=0; i<ln ;i++) ret += buf[i] + ar[i];
    return ret;
    }

0: https://pharr.org/matt/blog/2018/04/18/ispc-origins.html

1: https://ispc.github.io/

2: https://pharr.org/matt/blog/2018/04/26/ispc-volta-more-on-pe...