* MEMSET6 - MVCL
MEMSET6 CSECT ,
* ASSUMES R13=A(SAVEAREA), R14=A(RETURN), R15=A(MEMSET), R1=A(PARAMS)
* PARAMS: S=A(AREA TO SET), C=INT WITH C IN LOW BYTE, N=INT COUNT
         USING *,15          USE R15 AS BASE REG
         STM   2,5,12(13)    SAVE REGS WE USE
         LM    2,4,0(1)      LOAD PARAMS S, C, N
         LA    2,0(,2)       CLEAR HIGH-ORDER BITS OF ADDRESS
         LTR   2,2           VALID MEMORY ADDRESS > 0?
         BNP   ALLDONE       NO, JUST EXIT
         LTR   4,4           VALID LENGTH > 0?
         BNP   ALLDONE       NO, JUST EXIT
         C     4,MAXLEN      VALID LENGTH <= MAXLEN?
         BH    ALLDONE       NO, JUST EXIT
         SLL   3,24          SHIFT FILL BYTE TO HOB OF R3 + 0 LENGTH
         LR    5,4           MOVE DEST LENGTH INTO R5
         LR    4,2           COPY ADDRESS TO R4
         MVCL  4,2           MOVE C TO S FOR LENGTH N
ALLDONE  DS    0H            RETURN TO CALLER
         LM    2,5,12(13)    RESTORE REGS WE USED
         L     15,0(,1)      RETURN ORIGINAL S
         BR    14            GO BACK TO CALLER
         CNOP  0,4           ALIGN ON FULLWORD BOUNDARY
MAXLEN   DC    X'00FFFFFF'   MAX LENGTH THAT CAN BE MOVED
         END   MEMSET6      ALL DONE