A Novel Two-Level Instruction Issue Window Based on VLIW Architecture

Abstract

Instruction compression technique overcomes the drawbacks of traditional VLIW architectures with low density in the instruction cache. However, the separated long instruction word was arranged into two cache line. It comes to be a bottleneck problem for VLIW architecture processor performance because these split long instruction word can not be fetched and issued simultaneously. A novel two-level instruction issue window mechanism is proposed in this paper. It solves the instruction fetch and issue problem in separating instruction words. It provides more effective and continuous instruction flow, and stores one iteration of the loop body to support software pipeline technique, which improves VLIW DSP processor performance effectively. Proposed machanism was synthesized to evaluate its overall costs, and the performance speedup result for DSP/IMG library bencharks using the cycle accurate simulator are presented.