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Comment by zyedidia | Hacker News Reader

I think one of the interesting aspects of WebAssembly compared to JavaScript is that it can be efficiently AOT-compiled. I've been interested in investigating AOT compilation for a browser (perhaps there is a distant/alternative future where web browsing does not require a JIT), but maybe Wasm AOT compilers aren't really there yet.

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Functionally what browsers do under the hood is AOT compilation but not in the way that i.e. Wasmtime is. The following is my knowledge that may no longer be accurate, but this is the sort of model we planned for when designing WASM to begin with:

Browsers do a on-demand 'first tier' compilation for fast startup, and in the background using threads they do a high quality AOT compilation of the whole module. That high quality AOT compilation is cached and used for future page loads.

It is possible to use a JIT model for this but AFAIK it is typically not done. In some configurations (i.e. lockdown mode) WASM is interpreted instead of AOT compiled.

> It is possible to use a JIT model for this but AFAIK it is typically not done.

Isn't this what the last line of the article is hinting at? > our WebAssembly team is making great progress rearchitecting the Wasm compiler pipeline. This work will make it possible to Ion-compile individual Wasm functions as they warm up instead of compiling everything immediately.

I believe this is still true. Originally you could store a compiled wasm module in IndexedDB and cache it manually, but that was removed in favor of {instantiate,compile}Streaming, which take a HTTP response and hook into the existing HTTP caching layer, which was already storing the compliation output for JS.

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