converting small thing into ASM

[tester]

I just found another piece, that could save (very little but some) CPU due to need of reusing pack/unpack on the go. How to convert this one into mono4 single ASM piece? (Multipliers are used instead of selectors/multiplexers to avoid code resets on switch; I guess this one is not doable in code due to different operations on channels?). Correct me if I'm wrong (i.e. if there is no benefit from such conversion).

[MyCo]

This one only works with the first 2 channels of packed mono. The other 2 channels are overwritten, by a copy of the first 2.

[tester]

Thanks!

Good learning tool for getting some basics on the go.