Branch prediction unit in service of short microcode flows

Abstract

Disclosed embodiments relate to the usage of a branch prediction unit in service of performance sensitive microcode flows. In one example, a processor includes a branch prediction unit (BPU) and a pipeline including a fetch stage to fetch an instruction specifying an opcode, an operand, and a loop condition based on the operand, wherein the BPU is to generate a hint reflecting a predicted result of the loop condition, a decode stage to generate either a first or a second micro-operation flow as per the hint, the pipeline to begin executing the generated micro-operation flow; a read stage to read the operand and resolve the loop condition; and execution circuitry to continue the generated micro-operation flow if the prediction was correct, and, otherwise, to flush the pipeline, update the prediction, and switch from the generated micro-operation flow to the other of the first and second micro-operation flows.