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Global History Branch Prediction Updating Responsive to Taken Branches

  • US 20090198984A1
  • Filed: 01/31/2008
  • Published: 08/06/2009
  • Est. Priority Date: 01/31/2008
  • Status: Active Grant
First Claim
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1. In a microprocessor system using pipelined instruction processing, a method for updating a global history prediction record, the method comprising:

  • accepting a first microprocessor instruction of consecutive operations, including a first conditional branch operation with an associated first branch address, at a first stage in a pipelined microprocessor execution process;

    accessing a current value from a global history record (GHR) of conditional branch resolutions and predictions;

    hashing the current global history record value with the first branch address, creating a first hash result;

    using the first hash result to access an indexed branch history table (BHT) of branch direction counts;

    using the BHT, making a first branch prediction;

    in response to the first branch prediction being “

    taken”

    , left-shifting the current GHR value;

    hashing the left-shifted GHR with the first branch address, creating a second hash result; and

    ,using the second hash result, creating an updated GHR.

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