🚀 go-pugleaf

Girls and Boys,

In z/OS V1R3 and using HLASM R4, the following lines of assembler coding:
     MAINPGM  CSECT
     MAINPGM  AMODE 64
     MAINPGM  RMODE ANY
              SYSSTATE AMODE64=YES  <-- !!!
     PROLOG   SAVE  (14,12)
expand into:
     PROLOG   DS    0H
              STMG  14,12,8(13)     <-- !!!
Cf. the Store Multiple "Grande" (STMG) instruction:
Seemingly, the SAVE macro assumes there is a caller-provided 144-byte Format 
4 save area available to save the ENTIRE 64-bit contents of R14-R12.

1st question:
For a main program, the caller is the system (z/OS).
What kind of save area is supplied by z/OS V1R3 (and later)?
Is it still a traditional 72-byte "Format 0" save area or is it a new 
144-byte Format 4 save area?
Or does the type of save area provided by z/0S depends upon the AMODE of the 
(main) program?

In the same assembler source, i.e. still under control of SYSSTATE 
AMODE64=YES, the macro call
            RETURN (14,12),RC=0
expands into:
            LMG   14,12,144(13)     <-- !!!
            LA    15,0(0,0)
            BR    14
Cf. the Load Multiple "Grande" (LMG) instruction:
Seemingly, the RETURN macro also assumes the caller-provided save area to be 
of type Format 4.

2nd question:
- The distance 144 used by LMG goes beyond the 144-byte save area!
- 144 happens to be the offset in a (208-byte) Format 5 area used to 
save/restore the HIGH HALVES of R0-R15!
What point am I missing (or is it a bug)?

BTW, the LMG is the cause for a S0C4 with reason code 11. Not a surprise to 
me.

The complete JCL is:
//ARCIS07X JOB 'HLASM',CLASS=A,MSGCLASS=X,COND=(0,NE),NOTIFY=&SYSUID
//STEP1    EXEC PROC=ASMACLG,PARM.C=ASA  HLASM Release 4 - z/OS V1R3
//C.SYSIN   DD  *
MAINPGM  CSECT
MAINPGM  AMODE 64
MAINPGM  RMODE ANY
         SYSSTATE AMODE64=YES
PROLOG   SAVE  (14,12)
         BALR  R12,R0
         USING *,R12
         LA    R11,SAVEAREA
         ST    R11,8(R13)
         ST    R13,SAVEAREA+4
         LR    R13,R11
*
EPILOG   L     R13,SAVEAREA+4
         RETURN (14,12),RC=0
SAVEAREA DC    18F'0'
         YREGS
         END
/*
//L.SYSIN   DD  DUMMY

TIA for the response.

Michel
--------------------------------------------------
Michel Castelein - Arcis Services
MVS-OS/390-z/OS system engineer & instructor
arcisATadvalvasDOTbe
http://www.geocities.com/michelcastelein/