METHOD AND APPARATUS FOR PREDICTING FORWARDING OF DATA FROM A STORE TO A LOAD

摘要

A method for gating a load operation based on entries of a prediction table is presented. The method comprises performing a look-up for the load operation in a prediction table to find a matching entry, wherein the matching entry corresponds to a prediction regarding a behavior of the load operation, and wherein the matching entry comprises: (a) a tag field operable to identify the matching entry; (b) a distance field operable to indicate a distance of the load operation to a prior aliasing store instruction; and (c) a confidence field operable to indicate a prediction strength generated by the prediction table. The method further comprises determining if the matching entry provides a valid prediction and, if valid, retrieving a location for the prior aliasing store instruction using the distance field. It finally comprises performing a gating operation on said load operation.

主权项

1. An apparatus for gating a load operation, said apparatus comprising:
a memory resident data structure, wherein said memory resident data structure is a prediction table comprising a plurality of entries, wherein a matching entry corresponding to said load operation within said prediction table comprises a prediction regarding a dependence of said load operation on a prior aliasing store instruction, and wherein said matching entry comprises:
a tag field operable to identify said matching entry;a distance field operable to indicate a distance of said load operation to said prior aliasing store instruction; anda confidence field operable to indicate a prediction strength generated by said prediction table, wherein said prediction strength influences a gating of said load operation; and a gating circuit in a microprocessor pipeline configured to:
perform a look-up for said load operation in said prediction table to find said matching entry;determine if said matching entry provides a valid prediction by comparing said confidence field for said matching entry with a threshold value;responsive to a determination of a valid prediction, retrieve a location for said prior aliasing store instruction using said distance field; andperform a gating operation on said load operation.