Branch prediction and its impact on performance
Modern processors use branch prediction to guess the outcome of conditional operations (branches) before they are executed, allowing the CPU to preload instructions and maintain pipeline efficiency. When the CPU encounters a branch, such as an if statement or loop, it must decide which set of instructions to execute next. Incorrect predictions lead to pipeline flushes, where preloaded instructions are discarded, causing the CPU to idle while the correct instructions are fetched, significantly impacting performance.
The efficiency of branch prediction depends on the predictability of the code’s branching behavior. Predictable patterns allow the CPU’s branch predictor to make accurate guesses, minimizing stalls and maintaining high execution throughput. Conversely, unpredictable patterns can lead to frequent mispredictions, increased pipeline flushes, and reduced performance.
Optimizing code for branch prediction involves...
