Deferred branch history update scheme

A method comprising:

• generating an index to a branch prediction array in a processor, wherein the branch prediction array stores a plurality of branch predictions for conditional branches, the generating comprising logically combining at least:
• (i) at least a portion of a fetch address corresponding to a fetch request that is at a first pipeline stage of the processor;
• and (ii) a branch history;
• updating the branch history responsive to at least a first fetch request at the first pipeline stage;
• and
• deferring an update for at least a second fetch request to a second pipeline stage subsequent to the first pipeline stage, wherein instructions corresponding to the second fetch request are scanned to identify conditional branches at the second pipeline stage.

A processor comprising:

• a branch prediction array configured to store a plurality of branch predictions for conditional branches;
• an index generator coupled to the branch prediction array, wherein the index generator is configured to generate an index to the branch prediction array to read at least one of the plurality of branch predictions, wherein generating the index comprises logically combining at least:
• (i) at least a portion of a fetch address corresponding to a fetch request that is at a first pipeline stage of the processor;
• and (ii) an active branch history maintained by the index generator;
• and
• a control unit coupled to the index generator, wherein the control unit is configured to update the active branch history maintained by the index generator responsive to a first fetch request at the first pipeline stage, and wherein the control unit is configured to restore the active branch history maintained by the index generator to a state prior to the update for the first fetch request at a second stage of the pipeline at which instruction corresponding to the first fetch request are scanned to identify conditional branches.