Decoupling recovery mechanism for data speculation from dynamic instruction scheduling structure

Abstract

In this paper, we propose to decouple the recovery mechanism for data speculation from dynamic instruction scheduling structure. Instruction reissue mechanism for data speculation has a serious impact on processor performance. The effective capacity of instruction window is reduced since instructions dependent upon a speculated instruction must remain in instruction window until they are committed. The decoupling of the recovery and scheduling mechanisms solves the problem. A small instruction window schedules instructions and its entry is released immediately when an instruction is dispatched. A large instruction buffer is active only when a misspeculation occurs and is used to reissue instructions dependent upon the misspeculated instruction. Using a cycle-by-cycle simulator, we evaluated the proposal and found that the decoupling is useful. © Springer-Verlag Berlin Heidelberg 1999.