Code sequence for asynchronous backing store switch utilizing both the

Abstract

A computer implemented method for switching from an interrupted context to an interrupting context in a processor is provided. The processor includes a register stack (RS) that has first and second portions. The processor includes a register stack engine (RSE) that exchanges information, in one of instruction execution dependent and independent modes between the second portion and a storage area. The method includes the following steps: a state of the RSE of the interrupted context is preserved; a COVER instruction is issued; a first (BSPSTORE) pointer is preserved. The first pointer points to a location in the storage area, of the interrupted context, where a next register of the second portion is to be written; first pointer is written with a value corresponding to the interrupting context; and a second pointer (BSP) is preserved. The new first and second pointers in the interrupting context define the storage area of RS values associated with the interrupted context. The new first pointer is subtracted from the second new pointer. The difference (number of dirty registers) is deposited into the RSC.loadrs field. A LOADRS instruction is issued to load the RS with all interrupted context values. The original first BSPSTORE is restored from the preserved BSPSTORE.