[creata]

Why? My only guess is that the instructions don't match x86 instructions well (way too few Wasm instructions) and the runtime doesn't have enough time to compile them to x86 instructions as well as, say, GCC could.

[HPsquared]

To be fair, x86 instructions don't match internal x86 processor architecture either.

[201984]

How don't they? Most x86 instructions map to just one or two uops as you can see at https://uops.info