[rav]

You could use handwritten asmjs in that case. I did it at work to improve performance on some pixel-wise software rendering we were doing. (We have since then switched to WebGL, but asmjs was a nice stepping stone.) If I recall correctly, it basically boils down to using small fixed size arrays and appending "|0" after each uint32 operation and "+" in front of each float32 operation - so it's something you can do by hand. Of course, one of my colleagues then made a tweak which gave a surprisingly huge slowdown - you should probably declare loudly (with comments etc.) that a certain code block is intended to be asmjs if you do this in a large codebase.

[TekMol]

asmjs is great. Imho the better approach than wasm. But it seems to not have great browser support (no Safari for example). And support is probably not getting better in the future.