[fractalsea]

OK, so are you saying that compiling the language's runtime environment, including the GC, to asm.js would not be efficient enough? That makes sense.

I guess I was hoping that there may be some way to compile the runtime such that the GC wouldn't need to be compiled, and the GC of whatever is interpreting the asm.js code (e.g. SpiderMonkey) could be used instead.

[DougBTX]

That's roughly what happens when TypeScript gets compiled to JavaScript, it can use the browser's GC. asm.js is used to avoid the browser's GC, either when the original code doesn't need a GC since it uses manual memory management, or it uses a different type of GC from the browser and wants to use that instead (which is effectively the same thing).