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Explicit References to Base Registers and Displacements in OS VS, DOS VS and VM 370 Assembler Language

IP.com Disclosure Number: IPCOM000087564D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Gschwend, A: AUTHOR

Abstract

At present there are two common ways for referencing general registers, namely, reference by register number and symbolic reference.

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Explicit References to Base Registers and Displacements in OS VS, DOS VS and VM 370 Assembler Language

At present there are two common ways for referencing general registers, namely, reference by register number and symbolic reference.

While these reference capabilities are sufficient for computational registers, they are in some cases inadequate for base registers. Thus, there should be an additional capability for referring to a base register by means of any symbol within the addressing range of that register.

Assuming the R' symbol format for such references, the following examples result: USING DSECTX,R6 LA R'DSECTX,AREA1 LA R'DSECTX,L'AREA1(,R'DSECTX) DROP R'DSECTX.

Similar coding is possible, for example, by equating RDSECTX to R6, but this requires an additional definition, whereas with the R' symbol notation, any symbol within the first 4K of DSCETX can be used.

At present it is not possible to specify the displacement of a location from its base without knowing the first operand of the corresponding USING statement. In some cases (for example, in a macro-definition) this knowledge is usually missing.

Assuming the 0' symbol (0 for Offset) format for displacement references, the location "NAME" indexed with "TEMPREG" could be tested for blank by means of AR TEMPREG,R'~AME CLI O'NAME(TEMPREG),C' '. which is more economical than LA TEMPREG,NAME(TEMPREG) CLI O(TEMPREG),C' '

Here, existing assembler language restrictions prevent the generation of an optimum co...