"IBM Mainframe Assembler List" <ASSEMBLER-LIST@LISTSERV.UGA.EDU> wrote on
01/20/2022 12:28:53 PM:
> I'm aware of a 72-byte format and several 144-byte formats; I'm not
> aware of a 128 byte format. 128 bytes would not allow space for both
> a prefix and the top halves of the GRs.
Yes, a 128-byte savearea is sufficient because the Assembler
Service manual states that a calling program expects upon return:
• The low halves (Bits 32-63) of GPRs 2 - 13 are unchanged
• The high halves (Bits 0-31) of GPRs 2 - 14 are unchanged
• The remaining registers are all unchanged
The 72-byte savearea provides for the first bullet point and an
additional 56 bytes (for a total of 128 bytes) would provide for the
second bullet point. So, the only reason for additional savearea space is
if the called program is going to modify the other registers as well as
the general purpose registers.
The only issue is that in z/VSE I don't know if the caller is
providing a 72-byte savearea or a 128+byte savearea. So, I have to
compensate for anything above 72 bytes.
Sincerely,
Dave Clark
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