Since all languages should be able to compile to wasm, that question is pretty close to "Which language is the most performant?", which is a can of worms that I'm not going to open. Maybe something like the Benchmarks Game would be useful here. Or already exists, and someone could point me to it :)

A similar question would be "What languages do you know of that are focused on performance and compiling to wasm?" For that, I'd say C++, Rust, and Go, though I'm sure there are others.