Different structures for storing predicted branch destinations and their corresponding target instructions significantly impact processor performance. These structures, essentially specialized caches, vary in size, associativity, and indexing methods. For example, a simple direct-mapped structure uses a portion of the branch instruction’s address to directly locate its predicted target, while a set-associative structure offers multiple possible locations for each branch, potentially reducing conflicts and improving prediction accuracy. Furthermore, the organization influences how the processor updates predicted targets when mispredictions occur.
Efficiently predicting branch outcomes is crucial for modern pipelined processors. The ability to fetch and execute the correct instructions in advance, without stalling the pipeline, significantly boosts instruction throughput and overall performance. Historically, advancements in these prediction mechanisms have been key to accelerating program execution speeds. Various techniques, such as incorporating global and local branch history, have been developed to enhance prediction accuracy within these specialized caches.
