> That includes absurdities like "We should write a compiler from JavaScript to wasm to make all our JS faster!"
Is this this absurd? Given you can compile WASM whilst streaming, you should really precompile your JS into WASM if you can.
Is this this absurd? Given you can compile WASM whilst streaming, you should really precompile your JS into WASM if you can.
Yes, it is absurd. Because your wasm that was compiled from JS needs to embed an entire implementation of the dynamic nature of JS. And to make all those dynamic features remotely fast, you cannot just compile them as is. You need to use a JIT to be able to perform speculative optimizations. But then, where's the JIT? Oh, it's built inside your wasm code. And basically you end up shipping a JS interpreter+compiler+JIT as part of your wasm, instead of just the .js code. Parsing and compiling all of that will be much, much worse than parsing the .js code and feed it to the already existing JS interpreter+compiler+JIT that is in the browser.
Whether that's useful in practice is an open question, but it's plausible.
There is virtually no human-written JS code that is amenable to compilation to wasm in a meaningful way. At the very least, you need a (mostly) sound type system to be able to compile to wasm with a positive expected ROI.
The speed of wasm comes in a large part from the fact that it is entirely statically typed, which means we don't need the speculative optimizations (and their deoptimization guards) all over the place.