POS_C
#define GETARG_C(i) getarg(i, POS_C, SIZE_C)
#define SETARG_C(i,v) setarg(i, v, POS_C, SIZE_C)
| (cast(Instruction, c)<<POS_C))
#define POS_B (POS_C + SIZE_C)
#define POS_Bx POS_C