Automatic cache prefetch timing with dynamic trigger migration

Abstract

Dynamic migration of a cache prefetch request is performed. A prefetch candidate table maintains at least one prefetch candidate which may be executed as a prefetch request. The prefetch candidate includes one or more trigger addresses which correspond to locations in the instruction stream where the prefetch candidate is to be executed as a prefetch request. A jump history table maintains a record of target addresses of program branches which have been executed. The trigger addresses in the prefetch candidate are defined by the target addresses of recently executed program branches maintained in the jump history table. A pending prefetch table maintains a record of executed prefetch requests. When an operation such as a cache miss, cache hit, touch instruction or program branch is identified, the pending prefetch table is scanned to determine whether a prefetch request has been executed. If a prefetch request has been executed, the prefetch candidate which was used to execute that prefetch request is updated. That is, a new trigger address in the prefetch candidate is selected in order to reduce access latency.