> -----Original Message-----
> From: IBM Mainframe Discussion List
> [mailto:[EMAIL PROTECTED] On Behalf Of Shmuel Metz (Seymour J.)
> Sent: Sunday, July 17, 2005 5:23 PM
> To: [email protected]
> Subject: Re: Highly used programs: any better replacements out there?
>
>
> In <[EMAIL PROTECTED]>, on 07/16/2005
> at 01:27 AM, Gerhard Postpischil <[EMAIL PROTECTED]> said:
>
> >Depends on what we're talking about. LA r,0 vs. SLR r,r probably is
> >irrelevant these days. LA r,0(s) vs. LA r,0(,s) isn't.
>
> Some processors have a 3-way adder in the I-unit and the performance
> is the same whether the base field is 0 or not.
>
> >And atrocities like LH r,=H'5' rather than LA r,5 are still timely.
>
> It gets worse[1]; I've seen stuff like LH r,FIVE with FIVE DC H'5'.
>
> [1] I have an even worse example, but nobody[2] would believe it.
>
> [2] Well, you've seen the code, so I know you would believe it.
>
> --
> Shmuel (Seymour J.) Metz, SysProg and JOAT
I may be able to top that. Somebody, who I guess started on a s/360,
wrote the following all through a routine:
MVC HALFWORD,0(R1)
LH R2,HALFWORD
...
STH R2,HALFWORD
MVC 0(2,R1),HALFWORD
Granted, R1 may or may not have been halfword aligned. I'm fairly sure
that doing an "unaligned" LH is a lot faster than an MVC to align the
data, then the LH. If this were a "once only", who cares. But it was in
a inner loop that was executed thousands of times per call to the
subroutine, which was called for every record being processed from a
particular file.
--
John McKown
Senior Systems Programmer
UICI Insurance Center
Information Technology
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