— - rendering work on a CPU is usually so slow as to be not worth the bother at all, even with SIMD. GPUs do that way better, and already do in WebGL mode! Also, what makes you think WebGL mode is slow? It benchmarks upwards of twice as fast as canvas2d in most cases.
I am referring to WebGL effects, its utterly broken on mobiles as the performance hit is usually massive to a point of crippling performance on the latest hardware. So there is room for improvement right there.