IBM OS/390 13,413 Get backward chain pointer, Caller′ s save area, Restore the registers, Mvi

Under MVS, the RETURN macro returns control to the calling program and signals normal termination of the returning program. Control returns after restoring the address of the calling program′s save area into register 13. The return is made by executing a branch instruction using the address in register

14.You can write the RETURN macro to restore a designated range of registers, provide the proper return code in register 15, and flag the save area used by the returning program.

Sample MVS RETURN - using ′ T′ Operand:

L13,4(13) Get backward chain pointer

	RETURN	(3,6),T	(caller′ s save area)
+	LM	3,6,12(13)	Restore the registers
+	MVI	12(13),X′ FF′	Set return indicators
+	BR	14	Return
Sample MVS RETURN - Using ′Return Code′ Operand:
	LA	15,0	Set return code zero in R15

L13,4(13) Get backward chain pointer RETURN (14,12),RC=(15)

+	L	14,12(13,0)	Restore register 14
+	LM	0,12,20(13)	Restore registers 0 - 12
+	BR	14	Return

Note: You should have previously loaded a return code value into register 15.

Figure 29 on page 274 shows an example of MVS coding for initiation and termination procedures.

Chapter 13. A s s e m b l e r 273