Predicted return address from return stack entry designated by computation unit with multiple inputs including return hit flag and re-fetch signal

Abstract

An information processing apparatus is capable of speculatively performing an execution, such as a pipeline/superscalar/out-of-order execution and equipped with a branch prediction mechanism (a branch history). The information processing apparatus, in order to process an instruction sequence that includes a subroutine at a high speed, is further equipped with a return address stack, of which the stack operation is activated at a time of completing execution of an subroutine call/return correspondent instruction and an entry designating unit (pointer), in order to adjust a time difference resulting from an instruction fetch being executed prior to completing an instruction, pointing to a position relative to the stack front and adjusting a time difference between an instruction fetch performed speculatively in advance and completion of an instruction both at a time of completing execution of a branch instruction that is correspondent to a subroutine call/return and at a time of predicting a subroutine call/return in synchrony to the instruction fetch. An entry position correspondent to a stack position pointed to by the entry designation unit is adopted as a subroutine call/return prediction address and consequently the prediction of the subroutine return address becomes more accurate and the processing speed becomes higher.