Why the RISC instruction sets usually do not contain register to register copy instruction?

问题

I had this question on my exam and i am confused because as far as i know that

move $t0, $a0               # COPY $A0 TO $T0

in MIPS instruction provides that and MIPS is a RISC processor. Am I missing something?

回答1:

Move is a pseudoinstruction, and when assembled will really be a different instruction.

For instance

move $t0, $zero gets implemented as addu $t0, $zero, $zero

来源：https://stackoverflow.com/questions/53286335/why-the-risc-instruction-sets-usually-do-not-contain-register-to-register-copy-i