SCRF – A Hybrid Register File Architecture

In VLIW processor design, clustered architecture becomes a popular solution for better hardware efficiency. But the inter-cluster communication (ICC) will cause the execution cycles overhead. In this paper, we propose a shared cluster register file (SCRF) architecture and a SCRF register allocation algorithm to reduce the ICC overhead. The SCRF architecture is a hybrid register file (RF) organization composed of shared RF (SRF) and clustered RFs (CRFs). By putting the frequently used variables that need ICCs on SRF, we can reduce the number of data communication of clusters and thus reduce the ICC overhead. The SCRF register allocation algorithm exploits this architecture feature to perform optimization on ICC reduction and spill codes balancing. The SCRF register allocation algorithm is a heuristic based on graph coloring. To evaluate the performance of the proposed architecture and the SCRF register allocation algorithm, the frequently used two-cluster architecture with and without the SRF scheme are simulated on Trimaran. The simulation results show that the performance of the SCRF architecture is better than that of the clustered RF architecture for all test programs in all measured metrics.