Fencing off instruction buffer until re-circulation of rejected preceding and branch instructions to avoid mispredict flush

摘要

Systems and methods for handling the event of a wrong branch prediction and an instruction rejection in a digital processor are disclosed. More particularly, hardware and software are disclosed for detecting a condition where a branch instruction was mispredicted and an instruction that preceded the branch instruction is rejected after the branch instruction is executed. When the condition is detected, the branch instruction and rejected instruction are recirculated for execution. Until, the branch instruction is re-executed, control circuitry can prevent instructions from being received into an instruction buffer that feeds instructions to the execution units of the processor by fencing the instruction buffer from the fetcher. The instruction fetcher may continue fetching instructions along the branch target path into a local cache until the fence is dropped.