Browse Prior Art Database

Entry Point Identification Facility

IP.com Disclosure Number: IPCOM000086514D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Melkun, BF: AUTHOR

Abstract

The current technique for identifying an entry point to a module in most IBM S/370 programs is to provide an entry point address in general purpose register 15 for branching around an identified (ID) string at the entry point. This has the undesirable features that it depends on a correct entry value, it executes a branch, and it puts data (the ID string) into an instruction area.

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Entry Point Identification Facility

The current technique for identifying an entry point to a module in most IBM S/370 programs is to provide an entry point address in general purpose register 15 for branching around an identified (ID) string at the entry point. This has the undesirable features that it depends on a correct entry value, it executes a branch, and it puts data (the ID string) into an instruction area.

The alternative identification facility presented herein replaces the current assembler sequence at the entry point in a module by an NOP, the NOP including a halfword displacement to an ID string located outside the instruction area (for example, at the beginning or end of the module).

Examples: Current Identification Alternative Identification ENTRY DS OH ENTRY DS OH *SETUP USING FOR ADDRESSABILITY *SETUP USING FOR HALFWORD * DISPLACEMENT *OF THE BRANCH OPERAND *IN NOP OPERAND USING *,15 USING *,0,1,...,15

B AROUND NOP ID

DC ALI(AROUND-*) DROP 0,1,...,15

DC C `ID' ...

AROUND DS OH ID DC ALI(ENDID-*) DROP 15 DC C `ID'

... ENDID DS OH.

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