Loop fusion and reordering for register file optimization on stream processors

Wanyong Tian, Chun Jason Xue, Minming Li, Enhong Chen

Abstract: Stream processors are gaining popularity and getting deployed in many multimedia and scientific applications. stream register file (SRF) is a non-bypassing software-managed on-chip memory. Unlike conventional register files, the input data must be all stored in the SRF when a program is being executed. It is a critical resource in stream processors. When loading a program from the off-chip memory into SRF for execution, the storage consumption and the data transfer time are two key factors which affect the performance. This work applies loop transformation to programs for SRF optimization. We consider two objectives of minimizing the storage consumption and data transfer time. Previous techniques concentrate on the utilization of SRF only. This is the first paper considering both the two factors. We present a cost evaluation function in this paper and apply loop fusion and reordering to improve the performance of stream processors. The experimental results show significant performance improvement. Highlights ► Both storage consumption and data transfer time are considered for SRF optimization. ► The NP-hardness for all three cases is proved. ► Polynomial–time heuristics for all cases are proposed.