Looking at my "yellow card" , there MAY be a reason to use LA or L for
certain cases.
It looks like both SR and XR set the condition code, while L and LA do
not . So if one wanted to
preserve the CC for some reason, one could be justified in coding the L
or LA. So take a good look
at the subsequent stmts before replacing those Load opcodes !
Schuh, Richard wrote:
IIRC, the times for SR and XR were the same on the Amdahl machines, at
least on the ones that came after the 470. They may have been the same
on the 470, as well.
-----Original Message-----
From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On
Behalf Of Mike Walter
Sent: Monday, December 04, 2006 12:02 PM
To: IBMVM@LISTSERV.UARK.EDU
Subject: Re: CMSCALL return code
Sheesh, this goes way back to my good old Assembler diaper days when
programmers really cared about performance instead of drag and drop
solutions.
Slightly off-topic: if I remember correctly, we argued intensely about
zeroing a GPR and the performance differences between:
- SR R15,R15
- XR R15,R15
- LA R15,0 (not seriously considered by performance geeks)
- L R15,=F'0' (considered for use only by amateur programmers coming
from a BASIC or COBOL background and otherwise held in low esteem by
"real programmers"). ;-)
IIRC, the actual performance difference between SR and XR was different
based more on specific processor models that anything else.
Mike Walter
Hewitt Associates
Any opinions expressed herein are mine alone and do not necessarily
represent the opinions or policies of Hewitt Associates.
