Is there already a performance advantage with the current WASM implementations for number crunching code compared to writing plain Javascript? My experience is that modern JS engines are already pretty good at optimizing that kind of code, so I'm wondering if there are still significant speedups to be had by using WASM, given that it's still pretty new and didn't have much time to get optimized further yet.
For my emulator stuff (mostly bit twiddling on integers: https://floooh.github.io/tiny8bit/), I saw a very slight improvement of WASM vs asm.js on browsers that have special handling for asm.js (in the meantime I have dropped asm.js, and only compile to WASM, since all browsers support it).
On iOS Safari (which I guess doesn't have special asm.js handling) WASM is a whopping 3x..5x faster than running the same code compiled to asm.js.
The question now is how much slower 'idiomatic, handwritten Javascript' is on iOS Safari versus the same code written in C compiled to asm.js, but I think another 3x..5x slower is realistic.