>>        LR      R15,R3          Copy low 32-bits to R15
>>        SRLG    R0,R3,32                Copy upper 32-bits to R0

>You may want to add an SR or XR for register 0 and 15 prior to the 
>above two instructions if you want to make sure of the upper 
>32-bits of the target registers.

FWIW, you don't need to do anything to R0 prior to this because SRLG sets 
all 64 bits.
And of course you likely meant to do something to clear the high half of 
reg 15 (hence not SR, XR, in addition to instructions that are part of the 
high word facility introduced with z196, there are things like SGR, XGR, 
LGHI, LMH).

If there happens to be a requirement to preserve the high half of R0, SRLG 
into R0 by itself won't meet the needs.
 
Peter Relson
z/OS Core Technology Design


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