This isn't strictly baseless, but assuming that you return from the CALL
to the address in R14:
CALL SOMEFUNC
USING *,14
B JUMPTABLE(15)
DROP 14
JUMPTABLE DS 0H
J RC0
J RC4
J RC8
J RC12
-----Original Message-----
From: IBM Mainframe Assembler List
[mailto:[email protected]] On Behalf Of McKown, John
Sent: Friday, October 29, 2010 10:05 AM
To: [email protected]
Subject: Re: Modernizing code
The one place where I have found that I cannot replace a branch with a
branch relative is in a construct based on a return code:
CALL SOMEFUNC
B *+4(15)
J RC0
J RC4
J RC8
J RC12
and so on. The closest I can come, in baseless code, is:
CALL SOMEFUNC
LARL R10,JUMPTABLE
ALR R10,R15
L R10,0(,R10)
BR R10
JUMPTABLE DS 0F
DC A(RC0,RC4,RC8,RC12)
And if I understand it correctly, this will perform poorly due to
Address Generation Interlock.
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