Compiler driven data cache prefetching for high performance computers

Abstract

With advances in compiler optimization and program flow analysis, software assisted cache prefetching schemes using PREFETCH instructions are now possible. Although data can be prefetched accurately into the cache, the runtime overhead associated with these schemes often limits their practical use. We propose a new prefetching scheme, called the Embedded Data Prefetching (EDP), to prefetch array references with constant strides accurately. The basic idea of the EDP scheme is to store constant stride values of array references to be prefetched into a register array, called the stride register file. For each array reference r with constant stride s, the name of the stride register containing s will be embedded into the corresponding LOAD or STORE instruction for r. Then, prefetch hardware will use this embedded prefetching hint and its corresponding value in the stride register for accurate data prefetching. Compared to current software assisted data prefetching schemes, the EDP scheme has much lower runtime overhead without sacrificing prefetching accuracy. Our result showed that the EDP scheme is particularly suitable for computing intensive scientific applications where cache misses are mainly due to array references with constant strides and they can be prefetched very accurately by this EDP scheme. >