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Machine Assist for Software Subroutines

IP.com Disclosure Number: IPCOM000088017D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

McCauley, JN: AUTHOR [+3]

Abstract

The implementation of a hardware assist for a software subroutine is described. The assist implementation provides a transparent interface between the calling code and the called subroutine.

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Machine Assist for Software Subroutines

The implementation of a hardware assist for a software subroutine is described. The assist implementation provides a transparent interface between the calling code and the called subroutine.

The function of the assisted subroutine is invoked by a software defined CALL/RETURN protocol. The assist definition takes advantage of this information. The instruction which invokes the assist is inserted as the first instruction in the assisted subroutine. (See below.) When the subroutine is called, the assist feature is invoked. The assist feature first tests all conditions which prevent it from successful completion. If any such conditions exist, then the assist instruction degenerates to a NOOP and the normal software subroutine instructions are executed. Otherwise, the assist performs the function of the subroutine and uses the software linkage conventions to return control to the calling routine. CALLING ROUTINE CALLED SUBROUTINE . SUBA: instruction to invoke assist . . (instructions to .
. do function CALL SUBA . of subroutine . . in software) . RETURN

This implementation has a number of advantages. First, the assisted feature can be implemented with minimal software changes. No change to the CALL/RETURN protocol is required. Second, the assist can incorporate the RETURN protocol into its implementation. Third, software is not required to pretest any condition before invoking the assist.

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