Nope. asm.js as implemented in Firefox supports native integers and SIMD. SharedArrayBuffer gives you threads--but honestly this is a red herring, with apps barely making any use of multicore and iPhones being limited to 2 cores anyway. Web Assembly gives you 64 bit ints.<p>&quot;Compact, easy to parse bytecode&quot; is also irrelevant. JS is easy to parse. And the parser is such a tiny part of a JS engine it doesn&#x27;t matter at all in practice for complexity. It&#x27;s an aesthetic concern.<p>The actual performance problems Web apps hit have nothing at all to do with any of the areas you describe anyway. You think the Facebook app is making heavy use of custom SIMD or multicore? The SIMD support in Firefox gets barely any use because apps can&#x27;t find a use for it. Apple isn&#x27;t adding cores to their phones because apps aren&#x27;t using them. And so on.