_XREG
#define _X_RA _XREG(1)
#define _X_SP _XREG(2)
#define _X_GP _XREG(3)
#define _X_TP _XREG(4)
#define _X_T0 _XREG(5)
#define _X_T1 _XREG(6)
#define _X_T2 _XREG(7)
#define _X_S0 _XREG(8)
#define _X_S1 _XREG(9)
#define _X_A0 _XREG(10)
#define _X_A1 _XREG(11)
#define _X_A2 _XREG(12)
#define _X_A3 _XREG(13)
#define _X_A4 _XREG(14)
#define _X_A5 _XREG(15)
#define _X_A6 _XREG(16)
#define _X_A7 _XREG(17)
#define _X_S2 _XREG(18)
#define _X_S3 _XREG(19)
#define _X_S4 _XREG(20)
#define _X_S5 _XREG(21)
#define _X_S6 _XREG(22)
#define _X_S7 _XREG(23)
#define _X_S8 _XREG(24)
#define _X_S9 _XREG(25)
#define _X_S10 _XREG(26)
#define _X_S11 _XREG(27)
#define _X_T3 _XREG(28)
#define _X_T4 _XREG(29)
#define _X_T5 _XREG(30)
#define _X_T6 _XREG(31)