"IBM Mainframe Assembler List" <[email protected]> wrote on
04/01/2022 02:14:38 PM:
> Where I disagree is on the base register issue. Base registers and
> code addressability issues should have gone away. It is pretty
> trivial to replace old branches with their newer relative
> counterparts. Should be faster code, too, FWIW.
OK, I'll bite. This discussion has probably been done before but
I wasn't around for that. Forgive my newbie questions -- even though I
have been programming in assembler on and off since 1978. That said...
I understand relative branching on a basic level. But I haven't
really looked into them and haven't used them at all to this point. So...
1. Is it as simple as just using a different mnemonic for the branch?
2. Does the target label still have to be within 4K for the relative
branch?
3. ...or is there an extended relative branch that uses the extended
displacement feature?
4. What about the target for the EXecute instruction? Is there a relative
version of this?
5. Even if code base register(s) is(are) eliminated, you still need a data
base register -- yes?
6. If you have a large program with constant data at the end of the
program, how do you establish the base register needed for that data area?
7. Lastly, if the code base register has been eliminated, does this mean
you should no longer have things like LTORG at the end of each subroutine
to force data to be stored near the subroutine that uses it (where
previously the code base register for the subroutine would have served
double-duty as the data base register)?
Sincerely,
Dave Clark
--
Winsupply Group Services
3110 Kettering Boulevard
Dayton, Ohio 45439 USA
(937) 294-5331
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