[monocasa]

You can absolutely design the instruction decoder into two parallel decoders that decode AArch32 and AArch64 respectively. Splitting Thumb from the rest of AArch32 probably doesn't make sense, and on x86 it probably doesn't make sense to break out 32 and 64 bit, but I can absolutely see the case for AArch32 vs AArch64.

[arghwhat]

> You can absolutely design the instruction decoder into two parallel decoders that decode AArch32 and AArch64 respectively.

You can design anything. The question is whether the added design complexity (which for silicon directly translates to increased power consumption) outweighs the benefits.