But at that point the VM-atop-asm.js-atop-the-JavaScript-engine would be the thing doing the GC against its own asm.js-provided heap. (Right?) Perhaps performance would be awful, though I guess I don't immediately see why: if asm.js can get reasonably close to native speed (within 2x, I think I've read?) and .NET/Java can get within a comparable distance of native, then the two together should be slower, but not unusable for many things, I'd think.
Upon seeing your edit: much of the speedup also comes from the lack of dynamicity, too, from my understanding.
"VM-atop-asm.js-atop-the-JavaScript-engine would be the thing doing the GC"
"much of the speedup also comes from the lack of dynamicity, too."
In the language, JS gives you no control over its underlying GC. Every single assumption that asm.js leverages depends on the determinism, and introducing a GC into the mix really messes with AOT optimizations
But the JavaScript engine's GC isn't applicable here, is it? Because everything from the asm.js layer up is using a privately-managed heap implemented as a single (?) JavaScript typed array (ArrayBuffer) with no JavaScript-engine-level visibility of the distinct asm.js-layer values stored in it.
Edit: perhaps the thing I'm missing is that the discussion is about direct translation of CLR IL/JVM bytecodes into asm.js without any vestige of the CLR/JVM still running alongside. I was merely thinking of compiling the CLR or JVM to asm.js then hosting unmodified CLR IL/JVM bytecode atop that. Which seems feasible, though not as performant as a VM-less translation which I agree doesn't seem possible.
Upon seeing your edit: much of the speedup also comes from the lack of dynamicity, too, from my understanding.