Abstract: In one embodiment, a processor includes a performance monitor including a last branch record (LBR) stack to store a call stack to an event of interest, where the call stack is collected responsive to a trigger for the event. The processor further includes logic to control the LBR stack to operate in a call stack mode such that an entry to a call instruction for a leaf function is cleared on return from the leaf function. Other embodiments are described and claimed.

Abstract: An apparatus, method, and system are described herein for providing programmable control of performance/event counters. An event counter is programmable to track different events, as well as to be checkpointed when speculative code regions are encountered. So when a speculative code region is aborted, the event counter is able to be restored to it pre-speculation value. Moreover, the difference between a cumulative event count of committed and uncommitted execution and the committed execution, represents an event count/contribution for uncommitted execution. From information on the uncommitted execution, hardware/software may be tuned to enhance future execution to avoid wasted execution cycles.