From what I can tell, doing basic things like a property get on an object in WASM/host-bindings will require a spill to function, with no chance of specialization:
That comment (which I made) explains why probably the best we can expect for wasm accessing normal JS objects is the same level of speed as a modern JS engine's "tier 1"/"baseline" JIT. But the Rust code discussed in the OP wasn't accessing JS objects, it was accessing Rust memory which lives in wasm's "linear memory", so I don't see how my comment really disagrees with what jandem or dikaiosune are saying.
https://github.com/WebAssembly/host-bindings/issues/11#issue...
If you think the assembly in this article is bad, WASM/host-bindings appear to be even worse.