Am 12.05.2017 um 00:08 schrieb John McKown:
On Thu, May 11, 2017 at 4:55 PM, Bernd Oppolzer <bernd.oppol...@t-online.de>
wrote:
Yes, of course. I detected the error when I looked at
my piece of software from last year which examined the different LE heaps.
and: thank you, Allan Kielstra, for the clarification regarding Reg 12;
so my call to the ASSEMBLER function to get the address of the CEECAA will
work?
Here is the ASSEMBLER program which returns the registers (especially reg
12)
to the C program:
MDV9970 CSECT
MDV9970 AMODE 31
MDV9970 RMODE ANY
*
***************************************************************
* UNTERPROGRAMM ZUR ERMITTLUNG DER
* AKTUELLEN REGISTERSTAENDE UND ABLAGE
* IN EINEN C-BUFFER (DER ALS PARAMETER
* UEBERGEBEN WIRD). ZWECK DER UEBUNG:
* ZUGRIFF AUF CEECAA (COMMON ANCHOR AREA VOM LE)
* UND DAMIT AUF ANYHEAP UND BELOWHEAP
* BERND OPPOLZER / AUGUST 2016
***************************************************************
*
R0 EQU 0
R1 EQU 1
R2 EQU 2
R3 EQU 3
R4 EQU 4
R5 EQU 5
R6 EQU 6
R7 EQU 7
R8 EQU 8
R9 EQU 9
RA EQU 10
RB EQU 11
RC EQU 12
RD EQU 13
RE EQU 14
RF EQU 15
*
STM RE,RC,12(RD) REGISTER SICHERN
USING MDV9970,RF ADRESSIERUNG HERSTELLEN
L R3,0(R1) ADRESSE VOM BUFFER = 1. PARAMETER
MVC 0(52,R3),20(RD) REGISTER 0 BIS 12 AUS SA UEBERTR.
ST RD,52(R3) REGISTER 13 ABSPEICHERN
MVC 56(8,R3),12(RD) REGISTER 14 UND 15 AUS SA UEBERTR.
LM RE,RC,12(RD) REGISTER ZURUECKLADEN
BR RE UND RUECKSPRUNG
*
END MDV9970
Looks fairly good to me. For returning the 32 bit registers, that is. But
it seems to be "overkill" to me. The "guts" of the routine could be just:
STM R0,RF,12(RD) SAVE ALL REGS.
L R3,0(,R1) POINT TO RETURN AREA
MVC 0(64,R3),12(RD) MOVE REGS AT ENTRY
SLR RF,RF
BR RE
This does not use standard linkage, but is that really necessary? The only
possible abend would be on the MVC, if the routine is not called properly.
I included the SLR just to "zero" the return code. If the C code is
declared as returning "void" (e.g. "void MDV9970(regs) ;" where regs is
defined as "uint regs[16];" ) then R15 on exit is ignored.
But you should add a LM instruction to restore the registers,
for example R3. The original program is called inside a C function,
and I thought that the registers should be restored on exit in a (sort of)
standard way. This is expected by the surrounding C routine, IMO.
What I find most interesting:
if I set RF (or any other register) to zero, I always would code
XR RF,RF
you use
SLR RF,RF
it's a matter of style, or maybe what you learned first. I know of people
using SR RF,RF - but I never saw SLR RF,RF up until now. Nice :-)
There was once a discussion that you can tell the author of a piece of
software
from such style attributes ... not only with ASSEMBLER, but with other
languages (even C etc.), too. With other languages, it's maybe more the
style of writing, layout etc.
Kind regards
Bernd
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