Interestingly Thumb2 was dropped when going from Arm32 to Arm64. Perhaps the encoding was getting really complicated, and would've been even harder with 32 regi

Interestingly Thumb2 was dropped when going from Arm32 to Arm64. Perhaps the encoding was getting really complicated, and would've been even harder with 32 registers, and not being able to save a lot of memory (if many instructions use 4 bytes anyway). Maybe one could come up with an instruction encoding that encodes some number of instructions per cache line. Every time the cpu jumps to a new instruction (at cache line address + index), the whole cache line needs to be loaded into icache anyway, and could get decoded then -> internally they get represented in microcode anyway.