Program is running out of Base register Addressibilty

milind suman · New User Joined: 19 Aug 2009 Posts: 55 Location: Pune

Hi ,

My Assembler program is running out of Base register Addressibilty . I need to insert few lines of code comprising 30 bytes of Instruction size . I dont have any option to increase the base registers . Can something be done as a quick turnaround .

Thanks

enrico-sorichetti · Posted: Fri Feb 26, 2010 1:00 am

not without having a full understanding of the program workings.

milind suman · New User Joined: 19 Aug 2009 Posts: 55 Location: Pune

Is there any any Macro available which assigns the base registers correctly . .

enrico-sorichetti · Posted: Fri Feb 26, 2010 1:22 am

base register assignment depends on the program structure!
no macro will realize the addressing branch pattern of Your program.

most macros will simply fill a certain number of base registers with the proper values

milind suman · New User Joined: 19 Aug 2009 Posts: 55 Location: Pune

So , Is there any way/method to convert the existing program baseless .

Bill O'Boyle · Posted: Fri Feb 26, 2010 1:39 am

Many times, Assembler programs contain constants (defined to the Main CSECT and addressed off a CSECT base-register), which could be defined to an External CSECT (table) and brought into the program via an MVS LOAD Macro (Batch only) and addressed via their own base-register and DSECT?

Do you have a situation like this where constants like these could be removed and externalized?

Otherwise, it's just guesswork for us....

Bill

enrico-sorichetti · Posted: Fri Feb 26, 2010 1:52 am

MBabu · Posted: Fri Feb 26, 2010 10:31 am

Its a few years since I did assembler, but remember running into the same problems and was able to find a few bytes here and there with things like using smaller constants or different instructions to do the same thing. For example (and my memory of lengths and instructions may be a bit off here):
L R6,=F'2' -> LA R6,2(0,0) : 8 bytes -> 2 bytes
L R3,=F'523' -> LH R3,=H'523' : 8 bytes -> 6 bytes
S 2,=F'1' -> BCTR 2,0 : 8 -> 2

Basically this stuff is similar to what Bill mentioned about reducing the footprint of literals.
There are also immediate instructions (CLI, etc) that take up less space than instructions that reference storage.
Sometimes there are eye-catcher constants you can reduce the size of.

You might be able to reorganize literals or constants so that wasted space due to alignment is reclaimed. Be careful with that because there are some instructions and macros that still require alignment (not many though).

Some instructions set condition codes and perform similar functions as others that don't. This can let you remove condition code test instructions.

Finally (and this should have been first) sometimes there is an algorithm done inefficiently that can simply be rewritten in less code. There are some old tricks that save space for some tasks (using UNPK for conversion to hex, using TRT for reversing strings, etc) that might be smaller than code in the existing program (note any such change obviously requires extensive testing).

Of course, the best thing to do is create a new CSECT or two to isolate some of the function as external subroutines if that is possible.

PeterHolland · Posted: Fri Feb 26, 2010 3:07 pm

Following are 2 macro's I used for entering/exiting programs,
and also an example how to use them