US Patent 7624254 Segmented pipeline flushing for mispredicted branches

A processor pipeline is segmented into an upper portion—prior to instructions going out of program order—and one or more lower portions beyond the upper portion. The upper pipeline is flushed upon detecting that a branch instruction was mispredicted, minimizing the delay in fetching of instructions from the correct branch target address. The lower pipelines may continue execution until the mispredicted branch instruction confirms, at which time all uncommitted instructions are flushed from the lower pipelines. Existing exception pipeline flushing mechanisms may be utilized, by adding a mispredicted branch identifier, reducing the complexity and hardware cost of flushing the lower pipelines.