wasm: optimize & simplify sign extension

Rather than storing all the shifts in temporaries, we perform the correct
shifting without temporaries. This makes the runtime code more performant
and also the backend code is simplified as we have a singular abstraction.
f05e09a0cfLuuk de Gram committed on 6/11/2022, 5:38:00 PMparent18afcc3
1 file changedLine totals unavailable