TODO write this
#define B32POpRegZero 0x00 //0 0
#define B32POpRegAt 0x01 //1 at
#define B32POpRegV0 0x02 //2 ret0
#define B32POpRegV1 0x03 //3 ret1
#define B32POpRegA0 0x04 //4 arg0
#define B32POpRegA1 0x05 //5 arg1
#define B32POpRegA2 0x06 //6 arg2
#define B32POpRegA3 0x07 //7 arg3
#define B32POpRegT0 0x08 //8 gp0
#define B32POpRegT1 0x09 //9 gp1
#define B32POpRegT2 0x0A //10 gp2
#define B32POpRegT8 0x0B //11 tempa
#define B32POpRegT9 0x0C //12 tempb
#define B32POpRegSp 0x0D //13 sp
#define B32POpRegFp 0x0E //14 fp
#define B32POpRegRa 0x0F //15 retaddr