Some topic drift:
for one of my customers, I had to change some very old ASSEMBLER
programs (1980 era) because of
serious SIIS issues ... programs modifying static areas near the
instruction stream, thereby invalidating
cache lines and leading to performance issues.
One of the problem areas were IBM macros such as TIME DEC (IIRC), which
modify their inline parameter list.
The examples can be found on the web, I think. Other areas are inhouse
macros, which had the same or
similar issues.
There is a IMO clever idea at this customer's site:
if a global macro symbol &GBREN is set, all macros put their temporary
storage in a certain DSECT
which is then allocated/getmained at program startup (together with the
save area) and freed at the end.
The base register is 13 ... which is needed anyway to address the save
area.
This way, the SIIS problems disappear at the same time, because the
target addresses of the store
and move instructions of the macros now are far away from the
instruction stream.
I fixed most of the SIIS problems of my customer by "cheating" and
telling the programs that they were
RENT (by setting &GBREN), when in fact they were not. And then I
supplied a static area instead of the
dynamic area (which is used with true RENT) and addressed this area
using "dependent USING".
My question now:
what do you think of the idea asking IBM to provide a similar technique
(an optional parameter,
like MF=L and MF=E, which is present on almost all macros) on their
macros, so that the
definition of the work areas can be put in another (separate) DSECT ?
This would IMO make
the creation of RENT programs which include IBM macros so much easier
... and help us
solve some SIIS problems.
Kind regards
Bernd
Am 27.08.2024 um 15:10 schrieb Peter Relson:
...
Will the macros ever be "changed" from using "LA" or "LAE" to some long-displacement form
unconditionally? Surely "no". That's the same 6-byte vs 4-byte consideration.
Conditionally? Maybe. But only if a formal request is submitted. And it's more
likely to happen for those macros that are tool-generated (as many of the
macros created since the mid 80's are).
...
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