Arrgh! You're right, I said SRA but meant SLR.
That's how IBM documents standard return logic in the Assembler Services Guide:
SLR 15,15 Set return code of zero
So that question remains: I wonder why they use SLR instead of SR.
-----Original Message-----
From: IBM Mainframe Assembler List <[email protected]> On Behalf
Of John Melcher
Sent: Monday, August 10, 2020 3:00 PM
To: [email protected]
Subject: Re: Clearing a register
My 360/67 functional characteristics says
XR 1.25 microsec
SR 0.65 microsec
SLR 0.65 microsec
-----Original Message-----
From: IBM Mainframe Assembler List <[email protected]> On Behalf
Of Schmitt, Michael
Sent: Monday, August 10, 2020 2:56 PM
To: [email protected]
Subject: Re: Clearing a register
*** External email: Verify sender before opening attachments or links ***
Yes, only clear low 32-bits of 64-bit registers.
I've seen method #3 in IBM code or documentation, which makes one wonder why
they used it instead of SR.
I forgot about LA Rn,0.
-----Original Message-----
From: IBM Mainframe Assembler List <[email protected]> On Behalf
Of Mike Hochee
Sent: Monday, August 10, 2020 2:50 PM
To: [email protected]
Subject: Re: Clearing a register
I tend to use XR or XGR and LLIHF or LLILF. SRA does not operate against all
32 bits, and sometimes I do not want to think about extras like sign extension
with LHI. (I know, it's not much to have to think about) I suppose if you want
compatibility with machines of 30/40 years ago you might tend towards XR and SR.
My 2 cents worth,
Mike
-----Original Message-----
From: IBM Mainframe Assembler List [mailto:[email protected]] On
Behalf Of Schmitt, Michael
Sent: Monday, August 10, 2020 3:13 PM
To: [email protected]
Subject: Clearing a register
Caution! This message was sent from outside your organization.
There are many ways to set a register to binary zero. My question is, which is
the most efficient?
1. XR Rn,Rn
2. SR Rn,RN
3. SLR Rn,Rn
4. LHI Rn,0
5. Other instruction
6. Depends on hardware
7. Depends on other factors. (What?)
8. They all have equal performance
9. Method X has worse performance but other advantages. (What?)
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