> all languages that target LLVM (including C, C++, Fortran, Ada, Julia, Swift and others) can be used in WebAssembly.

Having LLVM doesn't mean that webassembly Just Works, in the same way that having LLVM doesn't mean that all of its architectures Just Work. And even after getting past the "hello world" stage, there's a lot of other work to do to make it more than just a toy.

Let's take Ada, for example. https://blog.adacore.com/use-of-gnat-llvm-to-translate-ada-a... talks about how to use Ada to build stuff for wasm, but you need to include https://github.com/godunko/adawebpack/ to make things work well. Someone had to write that code.

No, that is if you want runtime support, etc.

If you just want to run some computational code (which is the case for most of the Wasm use today), it will Just Work, as you say.

In fact, that is how I sped up a webpage: I just wrote myself the minimal support needed to run the code that computed X, and that's it. I don't want the entire world or standard library for computational bits to work.

The example I pointed out was for extra stuff, sure, but even just to get a compiler to spit things out, work needs to be done. I don't know Ada's compiler well enough to point to where that work is, but here's the initial implementation of the asmjs and wasm targets in rustc, for example https://github.com/rust-lang/rust/pull/36339

This is just true of any architecture. LLVM is a toolkit, it isn't magic.