REG_Z0 + 30,
		REG_Z0 + 31:
		if ctxt.Arch.Family == sys.I386 {
			return Yxxx
		}
		return Yzr

	case REG_K0:
		return Yk0

	case REG_K0 + 1,
		REG_K0 + 2,
		REG_K0 + 3,
		REG_K0 + 4,
		REG_K0 + 5,
		REG_K0 + 6,
		REG_K0 + 7:
		return Yknot0

	case REG_CS:
		return Ycs
	case REG_SS:
		return Yss
	case REG_DS:
		return Yds