Patent ID: 7454602
Filing Date: 2008-11-18
Classification: G06F

Abstract:
1. A method for updating global branch history (GBH) information in a pipelined instruction processing system, said method comprising: providing a branch history table having a plurality of entries, wherein each entry associates a branch instruction with a branch prediction value; providing a bifurcated GBH buffer that contains GBH information that is used to index into said branch history table to obtain a branch prediction signal, said bifurcated GBH buffer comprising: providing a fetch group pattern counter that counts the number of taken branch instructions within a single fetch group; providing a taken-branch flag that indicates whether a branch has been taken in a single fetch group; responsive to a next fetch group of instructions being fetched from an instruction cache, initializing said front-end GBH buffer by shifting a fixed number of GBH bits into said front-end GBH buffer, wherein said fixed number is independent of the number of branch instructions within said next fetch group; in further response to fetching said next fetch group, updating said back-end GBH buffer by performing the following steps: using the updated GBH bits in back-end GBH buffer to update the front-end GBH buffer.