RS2_SHIFT
#define rs2_index ((instr & RS2_MASK) >> RS2_SHIFT)
#define RS2_MASK (0x1f << RS2_SHIFT)
#define RS2_RA (X_RA << RS2_SHIFT)
rs2 = (insn & RS2_MASK) >> RS2_SHIFT;
#define RS2_MASK (0x1f << RS2_SHIFT)
rs2 = (insn & RS2_MASK) >> RS2_SHIFT;