? ITYM
L R10,PSATOLD-PSA(,0)
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
________________________________________
From: IBM Mainframe Assembler List [ASSEMBLER-LIST@LISTSERV.UGA.EDU] on behalf
of David Cole [dbc...@colesoft.com]
Sent: Thursday, June 1, 2023 1:49 PM
To: ASSEMBLER-LIST@LISTSERV.UGA.EDU
Subject: Re: Assembler theology question
WRT:
L R10,PSATOLD-PSA(,R9) Get current TCB
L R9,TCBJSCB-TCB(,R1) Get JSCB
In the specific case of the PSA, there is no need to load a base register.
Also, I probably wouldn't bother with a USING. My favorite
instruction for this is:
L R10,PSATOLD-PSA(0)
Note, providing the "0" for the index register prevents that rather
annoying ASMA306W message.
Dave Cole
At 6/1/2023 12:57 PM, Seymour J Metz wrote:
>R9? I might believe R0.
>In general, I prefer the code with USING over the code with explicit
>offset and base, although I might use the second if I'm only going
>to reference a single field in the control block. If I need to
>access multiple instances of the same control block, I would prefer
>to use a labeled USING or, in some cases, a labeled dependent USING.
> USING PSA,R0
> L R10,PSATOLD Get current TCB
> DROP R0
>THIS USING TCB,R10
> L R9,THIS.TCBJSCB Get JSCB
> l R11,THIS.TCBOTCB
>THAT USING TCB,R11
>--
>Shmuel (Seymour J.) Metz
>http://mason.gmu.edu/~smetz3
>________________________________________
>>From: IBM Mainframe Assembler List
>>[ASSEMBLER-LIST@LISTSERV.UGA.EDU] on behalf of Phil Smith III
>>[li...@akphs.com]
>>Sent: Thursday, June 1, 2023 12:24 PM
>>To: ASSEMBLER-LIST@LISTSERV.UGA.EDU
>>Subject: Assembler theology question
>>We've all seen (and written!) code like this:
>> USING PSA,R9
>> L R10,PSATOLD Get current TCB
>> DROP R9
>> USING TCB,R10
>> L R9,TCBJSCB Get JSCB
>> DROP R10
>>I've also seen (and probably written) the equivalent:
>> L R10,PSATOLD-PSA(,R9) Get current TCB
>> L R9,TCBJSCB-TCB(,R1) Get JSCB
>>I like the latter because it's tighter to read, reduces the USING
>>map, keeps you out of trouble if you decide to use R9 or R10 for
>>something global, etc. But I can also see a theological argument
>>that you really *are* using (USING?) the control block.
>>Thoughts? (Yes, I *said* it was theology, so I'm prepared for
>>religious arguments!)
