DATA PROCESSING APPARATUS AND METHOD EMPLOYING INSTRUCTION FLOW PREDICTION

A data processing system for processing a sequence of program instructions has a pipeline structure which includes an instruction pipeline and an execution pipeline. Each of the instruction and execution pipelines has a plurality of serially operating stages. The instruction pipeline reads instructions from storage and forms therefrom address data to be employed by the execution pipeline. The execution pipeline receives the address data and uses it for referencing stored data to be employed for execution of the program instructions. A program instruction flow prediction apparatus and method employ a high speed flow prediction storage element for predicting redirection of program flow prior to the time when the instruction has been decoded. Circuitry is further provided for updating the storage element, correcting erroneous branch and/or non-branch predictions, and accommodating instructions occurring on even or odd boundaries of the normally read double word instruction. Circuitry is further provided for updating the program flow in a single execution cycle so that no disruption to normal instruction sequencing occurs.