There's no AArch32 or Thumb support (A32/T32) on M-series chips. AArch64 (technically A64) is the only supported instruction set. Fun fact: this makes it impossible to run Mario Kart 8 via virtualization on Macs without software translation, since it's A32.
How much that does for efficiency I can't say, but I imagine it helps, especially given just how damn easy it is to decode.
How much that does for efficiency I can't say, but I imagine it helps, especially given just how damn easy it is to decode.