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Comment by fulafel | Hacker News Reader

WebAssembly is quite a small change from asm.js - it's mainly a different transfer format and a parsing speedup. It's targeted towards non-GC languages like C/C++ and Rust - for managed languages, Javascript is the only sane compile target.

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Scripts for GC languages wouldn't be compiled directly for WebAssembly -- their runtimes would. That's why I suggest browser vendors bless a few specific alternative runtimes and distribute them with the browser. For example, PyPy would be compiled for WebAssembly, and then Python could be executed directly as a client-side web language. Same with Dart and other languages that depend on a VM to do the heavy lifting.

> Scripts for GC languages wouldn't be compiled directly for WebAssembly -- their runtimes would

It is not a walk in the park to compile runtime into WebAssembly (unless you are just compiling an interpreter).

Performant runtimes usually include machine specific backends and/or hand written assembly code. You'll need to port that all to target WASM too.

Yeah, though I haven't worked on that directly, I'm sure it's not trivial, but I think there is sufficient demand. Check out http://pypyjs.org , which uses emscripten to compile to asm.js and then bolts on a custom JIT that emits asm.js, for one example of a project that is already trying something like this.

I guess if wasm some day gets GC support and runtime code generation, there might be something to this idea - for a language like OCaml that is designed for AOT compilation.

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