So far it seems like if you have some parsing or formatting task that can be trivially vectorized, the compiler will never do that, and you absolutely must use intrinsics.

I tried auto-vectorisation, and it worked pretty well. But the code became just as big as using intrinsics would have (that with explicitly unrolling loops and rearranging things in memory), and intrinsics generated code that was easily 35% faster.

I decided not put it off for later, and keep things simple for now.