Prefetch hardware efficiency via prefetch hint instructions

Abstract

A software agent assembles prefetch hint instructions or prefixes defined in an instruction set architecture, the instructions/prefixes conveying prefetch hint information to a processor enabled to execute instructions according to the instruction set architecture. The prefetch hints are directed to control operation of one or more hardware memory prefetcher units included in the processor, providing for increased efficiency in memory prefetching operations. The hints may optionally provide any combination of parameters describing a memory reference traffic pattern to search for, when to begin searching, when to terminate prefetching, and how aggressively to prefetch. Thus the hardware prefetchers are enabled to make improved traffic prediction, providing more accurate results using reduced hardware resources. The hints may include any combination of specific pattern hints (one/two/N-dimensional strides, indirect, and indirect-stride), modifiers including sparse and region, and a prefetch-stop directive. The parameters may include any combination of a count, a priority and a ramp.