Chris_Craddock@no-spam (Craddock, Chris) wrote: >
> Basically just convenience in some situations where you might
> not have a convenient base register. Its really intended for use
> by compilers because it may allow them to use the registers more
> productively.
>
> Chris
Hi Chris,
it's not only for convenience.
Branch relative is also more efficient because it does not need TLB
lookups for base/index register values. This may be not relevant for
application programs but may significantly improve frequently used
system routines and exits. AFAIK most of critical z/OS 1.4 internal
code uses relative instuctions when running in ARCHLVL 2.
In fact it makes compilers more effective because other processor
architectures (especially Intel x86) know relative instructions since
many years.
Regards,
Peter Pfaffner