🚀 go-pugleaf

Steve Comstock wrote:

>          LARL  R12,TEST64
>          USING *,R12


Ignoring the fact that the above USING is wrong, 64-bit programs are
intended to use relative addressing. Thus, the base register would
normally cover constants and literals only (for reentrant code) and the
work area (for non-reentrant code). That is, under normal circumstances,
the LARL would not point to the start of the program. I believe these
examples may be somewhat more typical:

Reentrant code:
|         LARL  R12,TEST64_Const    Point to constants area
|         USING TEST64_Const,R12    Synchronize base register
|         STORAGE OBTAIN,           Acquire the work area
|               LENGTH=WKAREA_LEN   Acquire work area
|         STG   R1,136(,R13)        Chain save areas
|         STG   R13,128(,R1)        (same)
|         LGR   R13,R1              Get area address in R13
|         USING WKAREA,R13          Synchronize WKAREA
|         .
|         .
|               CNOP  0,8           Align to doubleword
|TEST64_Const   DC    0D            Begin constants area
|               .
|               .
|               LTORG ,             Define literals
|
|WKAREA         DSECT ,             Program work area DSECT
|               DS    18D           Program save area
|               .
|               .
|WKAREA_LEN     EQU   *-WKAREA      Length of work area


Non-reentrant code:
|         LARL  R1,TEST64_Const     Point to constants area
|         STG   R1,136(,R13)        Chain save areas
|         STG   R13,128(,R1)        (same)
|         LGR   R13,R1              Get area address in R13
|         USING TEST64_Const,R13    Synchronize base register
|         .
|         .
|               CNOP  0,8           Align to doubleword
|TEST64_Const   DC    0D            Begin constants area
|               DC    18D'0'        Define program save area
|               .
|               .
|               LTORG ,             Define literals

--
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| Edward E. Jaffe                |                                |
| Mgr, Research & Development    | edjaffe@phoenixsoftware.com    |
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