Method and system for reduced run-time delay during conditional branch

Abstract

A method and system are disclosed for reducing run-time delay during conditional branch instruction execution in a pipelined processor system. A series of queued sequential instructions and conditional branch instructions are processed wherein each conditional branch instruction specifies an associated conditional branch to be taken in response to a selected outcome of processing one or more sequential instructions. Upon detection of a conditional branch instruction within the queue, a group of target instructions are fetched based upon a prediction that an associated conditional branch will be taken. Sequential instructions within the queue following the conditional branch instruction are then purged and the target instructions loaded into the queue only in response to a successful a retrieval of the target instructions, such that the sequential instructions may be processed without delay if the prediction that the conditional branch is taken proves invalid prior to retrieval of the target instructions. Alternately, the purged sequential instructions may be refetched after loading the target instructions such that the sequential instructions may be executed with minimal delay if the prediction that the conditional branch is taken proves invalid after loading the target instructions. In yet another embodiment, the sequential instructions within the queue following the conditional branch instruction are purged only in response to a successful retrieval of the target instructions and an imminent execution of the conditional branch instruction.