Reducing off-chip memory access via stream-conscious tiling on multimedia applications

Abstract

The iteration space of a loop nest is the set of all loop iterations bounded by the loop limits. Tiling the iteration space can effectively exploit the available parallelism, which is essential to multiprocessor compiling and pipelined architecture design. Another improvement brought by tiling is the better data locality that can dramatically reduce memory access and, consequently, the relevant memory access energy consumptions. However, previous studies on tiling were based on the data dependence, thus arrays without dependencies such as input arrays (data streams) were not considered. In this paper, we extend the tiling exploration to also accommodate those dependence-free arrays, and propose a stream-conscious tiling scheme for off-chip memory access optimization. We show that input arrays are as important, if not more, as the arrays with data dependencies when the focus is on memory access optimization instead of parallelism extraction. Our approach is verified on TI's low power C55X DSP with popular multimedia applications, exhibiting off-chip memory access reduction by 67% on average over the traditional iteration space tiling.