You need a NOP instruction, for many reasons (padding loops to cache line boundaries, jump tables, ...). This gets you free NOPs without allocating an instructi

You need a NOP instruction, for many reasons (padding loops to cache line boundaries, jump tables, ...). This gets you free NOPs without allocating an instruction encoding for it. The processor needs to optimize it, because otherwise the NOP-equivalents ADD zero, zero, zero ADD zero, zero, zero would take 2-3 cycles to complete, because it looks like the first is writing to a register that the second is reading from, creating a scheduling hazard. The AXP should be able to issue those side-by-side, knowing that they don't actually do anything.