Method and apparatus for minimizing overhead when executing nested do

Abstract

A data processing system having apparatus for selectively executing nested do loops with minimum overhead is provided. The apparatus may be added to a system which executes do loops. The method of execution of the do loops may be any of a myriad of conventional methods. Memory storage is provided for storing the number of iterations remaining in a do loop and an active loop flag. The active loop flag indicates that a do loop is active and enables the do loop apparatus. The active loop flag also indicates whether the data stored in memory is associated with an active loop. New parameters relating to the nested do loop may be used by the same circuitry which executes the do loop thereby eliminating duplication of circuitry. Upon termination of the nested do loop, the memory storage restores the information required to complete the do loop by the apparatus.