It's not just SSE2; SIMD.js also includes things like Int32x4.mul, which is a little tricky without SSE4.1's pmulld. It's kind of a balancing act between severa

It's not just SSE2; SIMD.js also includes things like Int32x4.mul, which is a little tricky without SSE4.1's pmulld. It's kind of a balancing act between several concerns. Also, it's a base, and we definitely plan to iterate and add more features on top of it.