[brucehoult]

Thumb2 -- which is the only ISA available on 32 bit Cortex M devices and the main ISA for a decade now on 32 bit Cortex A devices -- mixes 16 bit and 32 bit opcodes arbitrarily, with 32 bit opcodes frequently on 16 bit boundaries.

It's simply Not That Hard to deal with. You just need to have two 32 bit words in your instruction decode buffer. Sometimes you need the 1st half of the 2nd word and sometimes you don't.

Incidentally, once you've done that, arbitrarily aligned (on halfwords) 48 bit instructions don't need anything extra.