[pizlonator]

The wasm blob has to undergo the hardest parts of optimization to get native code from it. You need to select instructions and allocate registers. Those things are time consuming; they are on the same order of magnitude of time consumption than most full compiler pipelines.

Compiling wasm to native is only faster than downloading if you compile without optimization. That’s common in wasm VMs but then there’s an optimizing JIT that runs adaptively later, just like a JS or Java VM would do.

The fact that JS VMs share the ICU implementation between instances is a huge deal. That’s not the only thing that gets shared. Also, it’s not about just sharing code; it’s about sharing memory for the runtime’s state and for allowing elastic reuse of space for objects. In wasm the sharing is page granularity at best.