Linkage editor and binder support of AMODE and RMODE

The linkage editor accepts AMODE and RMODE specifications from any or all of the following:

Object modules.
Load modules.
PARM field of the linkage editor EXEC statement. For example:
```
//LKED EXEC PGM=name,PARM='AMODE=31,RMODE=ANY,.....'
```
PARM field input overrides object module and load module input.
Linkage editor MODE control statements in the SYSLIN data set. For example:
```
MODE AMODE(31),RMODE(24)
```
MODE control statement input overrides object module, load module and PARM input.

Linkage editor processing results in two sets of AMODE and RMODE indicators located in:

The load module
The PDS entry for the member name and any PDS entries for alternate names or alternate entry points that were constructed using the linkage editor ALIAS control statement.

These two sets of indicators might differ because they can be created from different input. The linkage editor creates indicators in the load module based on input from the input object module and load module. The linkage editor creates indicators in the PDS directory based not only on input from the object module and load module but also on the PARM field of the linkage editor EXEC statement, and the MODE control statements in the SYSLIN data set. The last two sources of input override indicators from the object module and load module. Figure 1 shows linkage editor processing of AMODE and RMODE.

Figure 1. AMODE and RMODE Processing by the Linkage Editor

The linkage editor and binder use default values of AMODE 24/RMODE 24 for:

Object modules produced by assemblers older than Assembler H Version 2 and High Level Assembler.
Object modules produced by Assembler H Version 2 where source statements did not specify AMODE or RMODE.
Load modules produced by linkage editors older than the MVS/XA linkage editor.
Load modules produced by the linkage editor that did not have AMODE or RMODE specified from any input source.
Load modules in overlay structure.

Treat programs in overlay structure as AMODE 24, RMODE 24 programs. Putting a program into overlay structure destroys any AMODE and RMODE specifications contained in the load module.

The linkage editor recognizes as valid the following combinations of AMODE and RMODE:

AMODE 24: RMODE 24
AMODE 31: RMODE 24
AMODE 31: RMODE ANY
AMODE ANY: RMODE 24
AMODE ANY: RMODE ANY

The linkage editor accepts the ANY/ANY combination from the object module or load module and places AMODE 31, RMODE ANY into the PDS (unless overridden by PARM values or MODE control statements). The linkage editor does not accept ANY/ANY from the PARM value or MODE control statement.

Any AMODE value specified alone in the PARM field or MODE control statement implies an RMODE of 24. Likewise, an RMODE of ANY specified alone implies an AMODE of 31. However, for RMODE 24 specified alone, the linkage editor does not assume an AMODE value. Instead, it uses the AMODE value specified in the CSECT in generating the entry or entries in the PDS.

When the linkage editor creates an overlay structure, it assigns AMODE 24, RMODE 24 to the resulting program.