Indirect addressing using a register

When you specify a register, SLIP normally uses the contents of the general purpose register to calculate an address. It uses the address space or data space associated with the related access register when all the following conditions are true:

CURRENT is specified, or defaulted to
The processor is in access register (AR) ASC mode
The indirect address starts with a register indirection.

SLIP will continue to use that space until changed explicitly by a qualifier.

CURRENT can reset the space by negating the space previously found through an access register. The LIST value shown in the following example provides three storage ranges, in pairs. In AR ASC mode, the first two ranges are associated with access register 3. The third range is associated with location 8000 in the primary space.

When no register indirection is specified, SLIP will use the current address space.

LIST=(CU.3R%,+3,+6,+9,CU.8000,+4)

The LIST parameter value shown in the following example, also provides three storage ranges. In AR ASC mode the first range, 3R% to 4R%, is associated with the space indicated by access register 3. The second range, 5R% to 6R%, is also associated with the space indicated by access register 3.

The associated space changes only when the symbolic CURRENT is explicitly specified for the third pair, 7R% to 8R%. The symbolic CURRENT in this example changes the associated space to that indicated by access register 7.

LIST=(CU.3R%,4R%,5R%,6R%,CU.7R%,8R%)

You can use the BEAR symbolic to capture data about a wild branch as follows:

SLIP SET,C=0C1,DATA=(BEAR,EQ,nn),A=SVCD,E

In this example, if SLIP were entered to process an ABEND 0C1 and if the last successful branch occurred from nn (for example a possible branch to low storage from nn), an SVC dump is to be taken. The value of the BEAR symbolic is contained within SDWABEA in the dump.

You can use the BPER symbolic in conjunction with a dynamic PER trap where the range for an activated trap can be unknown.

SLIP SET,IF,LPAMOD=(MYMOD,60),A=TARGETID,TI=TRP2,ID=TRP1,E
SLIP SET,SA,A=SVCD,RA=(1R?),DATA=(BPER?,EQ,00),ID=TRP2,E

In this example, these two traps constitute a dynamic PER activation chain. The author is interested in taking an SVC dump when the first byte of the storage buffer that register 1 points to at offset 60 into MYMOD becomes zero. Without the use of the symbolic, you can not reference the address of this buffer in the trap.