"y" 5-bit source 3 register for ALNV.PS (MICROMIPSOP_*_RS3)
"z" must be zero register
"C" 23-bit coprocessor function code (MICROMIPSOP_*_COPZ)
- "B" 8-bit syscall/wait function code (MICROMIPSOP_*_CODE10)
+ "B" 10-bit syscall/wait function code (MICROMIPSOP_*_CODE10)
"K" 5-bit Hardware Register (RDHWR instruction) (MICROMIPSOP_*_RS)
"+A" 5-bit INS/EXT/DINS/DEXT/DINSM/DEXTM position, which becomes