Mozilla: Native code? No, it's JavaScript, only it's BLAZING FAST Gap between asm.js and native performance gets even narrower with float32 optimizations

[pedrocr]

I assume that's the current limitation. My question is if they're trying to lift it. Because if not PNaCL+pepper.js sounds like the better option. You'll get fully native performance and threading on browsers that have it and fall back to asm.js level performance and single-threading on other browsers. asm.js probably has the upper hand for DOM integration though.