V4/nsys/reg.h

#define	R0	(0)
#define	R1	(-2)
#define	R2	(-3)
#define	R3	(-4)
#define	R4	(-5)
#define	R5	(-9)
#define	R6	(-6)
#define	R7	(1)
#define	RPS	(2)