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Re: "Using" statement? --

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JEmebius wrote:
> Anonymous wrote:
>> John W Kennedy <jwkenne@attglobal.net> wrote:
>>
>>> On 2012-07-13 12:12:09 +0000, Fritz Wuehler said:
>>>
>>>> John W Kennedy <jwkenne@attglobal.net> wrote:
>>>>
>>>> Didn't see Pete's post since I killfile everything from google
>>>>
>>>>> On 2012-07-12 15:36:32 +0000, Pete Nelson said:
>>>>>
>>>>>> On Friday, July 6, 2012 10:24:16 AM UTC-5, John W Kennedy wrote:
>>>>>>> But, as I say, if you are writing code expressly for 
>>>>>>> z/Architecture,>
>>>>>>> and use only the Branch Relative family of instructions, and put 
>>>>>>> all>
>>>>>>> your data in a separate CSECT or DSECT (or PSECT), you do not 
>>>>>>> need a>
>>>>>>> base register for your code CSECT. That&#39;s why the Branch 
>>>>>>> Relative>
>>>>>>> instructions were invented -- so that you have one more general>
>>>>>>> register to use for other purposes.
>>>>>>>
>>>>>> Basically true, although whether your literal pool and constants 
>>>>>> are in
>>>>>> a separate CSECT or the same CSECT as your executable code, a base
>>>>>> register is still needed to address the data.  For small programs, 
>>>>>> you
>>>>>> probably end up using just as many base registers either way; when 
>>>>>> the
>>>>>> size of your executable code approaches/exceeds 4K, then you start
>>>>>> avoiding register starvation by using relative branching.
>>>> It's true many people allocate additional base registers when code 
>>>> exceeds
>>>> 4K but there is another way around this and I have written and 
>>>> worked on
>>>> substantial pieces of code that use one code base register no matter 
>>>> how
>>>> large the CSECT. There is really no excuse to use more than one code 
>>>> base
>>>> register, and I am saying that in reference to OS/360, not just 
>>>> since the
>>>> branch relative and immediate facility came out.
>>> Back in the OS/360 days, frankly, I always regarded more than one 
>>> code base register (for which I generally used GR12 unless in a PL/I 
>>> environment, in which case I used GR11) as a sure sign that the 
>>> module had grown too big, and needed to be refactored.
>>
>> Agreed.
> 
> When I knew in advance that my OS/360 module would occupy more than 8 
> Kbytes (4096 bytes) and certainly less than 12 Kbytes I would define 
> registers GR12, GR11 and GR10 as base registers for the first 4K, the 
> second 4K and the last 4K, and load them in advance with the appropriate 
> values:
> <GR15>, <GR15> + 4096, <GR15> + 8192.
> 
> The most straightforward coding for this reads [use fixed-space font]
> 
> ABCDEFGH CSECT
>          USING 12,11,10
>          LR    12,15
>          LR    11,15
>          AH    11,=H'4096'
>          LR    10,15
>          AH    10,=H'8192'
>          .................
>          LTORG
>          DC    H'4096'     (I am not sure if this the correct printing 
> in the output listing)
>          DC    H'8192'
> 
> (Takes 18 bytes)
> 
> Programmers who dislike literals can of course code something like
> 
> IKJL     CSECT
>          USING 12,11,10
>          LR    12,15       Origin of CSECT to GR12
>          LA    11,2048     Number 2048 to GR11
>          SLL   11,1        Shift one bit to the left so as to obtain 4096
>          LA    10,2048     Number 2048 to GR10
>          SLL   10,2        Shift two bits to the left so as to obtain 8192
>          AR    11,12       Add contents of GR12 to contents of GR11, 
> obtaining <GR12> + 4096
>          AR    10,12       Add contents of GR12 to contents of GR10, 
> obtaining <GR12> + 8192
>          
> ................................................................................... 
> 
> 
> (Takes 20 bytes)
> 
> Enjoy this old and bygone(?) stuff!
> 
> Ciao: Johan E. Mebius
> 

Silly mistake: 8 Kbytes is of course 8192 bytes. Was too fast editing my post. Johan E. Mebius

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"Using" statement? hancock4@bbs.cpcn.com - 2012-07-06 06:52 -0700
  Re: "Using" statement? John W Kennedy <jwkenne@attglobal.net> - 2012-07-06 11:24 -0400
    Re: "Using" statement? hancock4@bbs.cpcn.com - 2012-07-06 10:15 -0700
    Re: "Using" statement? Fritz Wuehler <fritz@spamexpire-201207.rodent.frell.theremailer.net> - 2012-07-12 07:31 +0200
      Re: "Using" statement? John W Kennedy <jwkenne@attglobal.net> - 2012-07-12 22:09 -0400
    Re: "Using" statement? Pete Nelson <plnelsonoma@yahoo.com> - 2012-07-12 08:36 -0700
      Re: "Using" statement? John W Kennedy <jwkenne@attglobal.net> - 2012-07-12 22:13 -0400
        Re: "Using" statement? Fritz Wuehler <fritz@spamexpire-201207.rodent.frell.theremailer.net> - 2012-07-13 14:12 +0200
          Re: "Using" statement? John W Kennedy <jwkenne@attglobal.net> - 2012-07-13 13:57 -0400
            Re: "Using" statement? Anonymous <noreply@breaka.net> - 2012-07-15 05:54 -0400
              Re: "Using" statement? -  JEmebius <jemebius@xs4all.nl> - 2012-07-30 22:09 +0100
                Re: "Using" statement? -- JEmebius <jemebius@xs4all.nl> - 2012-07-30 22:13 +0100
                Re: "Using" statement? --- JEmebius <jemebius@xs4all.nl> - 2012-07-30 22:19 +0100
                Re: "Using" statement? --- woodag@trap.ozemail.com.au (Andy Wood) - 2012-07-31 06:22 +0000
                Re: "Using" statement? --- reply JEmebius <jemebius@xs4all.nl> - 2012-08-01 02:44 +0100
                Re: "Using" statement? - Fritz Wuehler <fritz@spamexpire-201207.rodent.frell.theremailer.net> - 2012-07-31 20:46 +0200
                Re: "Using" statement? - reply JEmebius <jemebius@xs4all.nl> - 2012-08-01 03:10 +0100
                Re: "Using" statement? - reply Fritz Wuehler <fritz@spamexpire-201208.rodent.frell.theremailer.net> - 2012-08-07 16:36 +0200
                Re: "Using" statement? - reply Nomen Nescio <nobody@dizum.com> - 2012-08-07 21:33 +0200
                Re: "Using" statement? - reply Clark F Morris <cfmpublic@ns.sympatico.ca> - 2012-08-07 18:13 -0300
                Re: "Using" statement? - "Michel Castelein" <arcis@advalvas.be.without.this.no.spam.tail> - 2012-08-03 11:13 +0200
                Re: "Using" statement? - Anonymous <nobody@remailer.paranoici.org> - 2012-08-03 13:05 +0000
                Re: "Using" statement? - Allodoxaphobia <knock_yourself_out@example.net> - 2012-08-03 13:29 +0000
                Re: "Using" statement? - WAB JEmebius <jemebius@xs4all.nl> - 2012-08-04 00:03 +0100
                Re: "Using" statement? - WAB Allodoxaphobia <knock_yourself_out@example.net> - 2012-08-04 03:14 +0000
                Re: "Using" statement? - Nomen Nescio <nobody@dizum.com> - 2012-08-06 15:15 +0200
  Re: "Using" statement? alistair.j.l.maclean@gmail.com - 2012-08-19 05:58 -0700
    Re: "Using" statement? John W Kennedy <jwkenne@attglobal.net> - 2012-08-19 13:15 -0400
      Re: "Using" statement? Nomen Nescio <nobody@dizum.com> - 2012-08-19 22:20 +0200
        Re: "Using" statement? John W Kennedy <jwkenne@attglobal.net> - 2012-08-19 18:30 -0400

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