Efficient fill-buffer data forwarding supporting high frequencies

摘要

A Fill Buffer (FB) based data forwarding scheme that stores a combination of Virtual Address (VA), TLB (Translation Look-aside Buffer) entry# or an indication of a location of a Page Table Entry (PTE) in the TLB, and a TLB page size information in the FB and uses these values to expedite FB forwarding. Load (Ld) operations send their non-translated VA for an early comparison against the VA entries in the FB, and are then further qualified with the TLB entry# to determine a “hit.” This hit determination is fast and enables FB forwarding at higher frequencies without waiting for a comparison of Physical Addresses (PA) to conclude in the FB. A safety mechanism may detect a false hit in the FB and generate a late load cancel indication to cancel the earlier-started FB forwarding by ignoring the data obtained as a result of the Ld execution. The Ld is then re-executed later and tries to complete successfully with the correct data.

主权项

1. A method comprising:
determining whether there is a hit in a first level of cache memory for a processor when a Load (Ld) instruction is processed for a first execution; and in the absence of the hit in the first level of cache memory, storing the following in a Fill Buffer (FB) of the processor:
a first Virtual Address (VA) provided by the Ld instruction, anda first indication of a location of a first Page Table Entry (PTE) in a Translation Look-aside Buffer (TLB) of the processor, wherein the first PTE is associated with the first VA provided by the Ld instruction.