As if to do almost the exact opposite of backing up my point, the PPC opcode I was thinking of is in fact `rlwimi' - Rotate Left Word Immediate then Mask Insert

As if to do almost the exact opposite of backing up my point, the PPC opcode I was thinking of is in fact `rlwimi' - Rotate Left Word Immediate then Mask Insert. I was thinking more like, Rotate Left and Insert Mask Word. Oh well. So maybe longer opcodes would help, but I'd have got it wrong in either event - and I'd still need to have double checked the docs, to remind myself, again, just what the hell it does exactly.