Control Independence Using Dual Renaming

Abstract

Modern Super scalar Processor squashes up all of wrong-path instructions when the branch prediction misses. In deeper pipelines, branch miss prediction penalty increases seriously owing to large number of squashed instructions. Exploiting control independence has been proposed for reducing this penalty. Control Independence method reuses control independent instructions (CI instructions) without squashing when branch prediction misses. Reusing CI instructions at branch miss prediction is not easy because of changing data dependency between squashed instructions and CI instructions. Conventional researches of CI architecture require complex Re-renaming mechanism, or with a limited applicability. This paper proposes a new mechanism named Dual Renaming for reusing CI instructions. It assigns two tags for each source register of CI instruction, and solves data dependency with simple mechanism when branch miss prediction is detected. The simulation result shows that Dual Renaming mechanism increases IPCs by maximum 29.52%.