I don't have a good overview but the last time I saw wasm-generated assembly it (e.g. firefox's compiler) was very very bad at actually using x86 addressing mod

I don't have a good overview but the last time I saw wasm-generated assembly it (e.g. firefox's compiler) was very very bad at actually using x86 addressing modes and other peephole-like "optimization" leading to high instruction counts and code size. This is something that will easily improve over time without a ton of work.