175 results about "Branch predictor" patented technology

The invention provides an instruction acquisition control method based on simultaneous multithreading, which includes the steps: in each clock cycle of a processor, reading a PC (personable computer) value of instructions by an instruction acquisition component according to a program counter, selecting two threads with high priority as instruction acquisition threads firstly, and then computing the actual instruction number required by each instruction acquisition thread so as to read the instructions; according to an IPC (inter-process communication) value and the Cache failure rate, enabling a dual-priority resource allocation mechanism to compute system resources required by the threads in an instruction acquisition stage and complete dynamic allocation of the resources; matching a TBHBP (thread branch history branch predictor) with the instruction acquisition operations of the instruction acquisition component, acquiring a pattern type match position Sc by connecting global historical information with local historical information read by a branch instruction Bi to utilize as an index of a secondary PHT (pattern history table), and inputting computed results to a BRT (branch result table); and when the branch instruction Bi is executed again, judging whether CONF fields are larger than or equal to 2 or not by the aid of a selector, directly outputting the recorded branch results if the CONF fields are larger than or equal to 2, and finally placing the acquired instruction into an instruction Cache, so that all operations of instruction acquisition control are completed.

An apparatus for executing branch predictor directed prefetch operations. During operation, a branch prediction unit may provide an address of a first instruction to the fetch unit. The fetch unit may send a fetch request for the first instruction to the instruction cache to perform a fetch operation. In response to detecting a cache miss corresponding to the first instruction, the fetch unit may execute one or more prefetch operation while the cache miss corresponding to the first instruction is being serviced. The branch prediction unit may provide an address of a predicted next instruction in the instruction stream to the fetch unit. The fetch unit may send a prefetch request for the predicted next instruction to the instruction cache to execute the prefetch operation. The fetch unit may store prefetched instruction data obtained from a next level of memory in the instruction cache or in a prefetch buffer.

A polymorphic branch predictor and method includes a plurality of branch prediction methods. The methods are selectively enabled to perform branch prediction. A selection mechanism is configured to select one or more of the branch prediction methods in accordance with a dynamic setting to optimize performance of the branch predictor during operation in accordance with a current task.

One embodiment of the present invention provides a system which improves branch prediction accuracy in a processor that supports speculative-execution. During normal-execution mode, the system issues instructions in program order. Upon encountering a launch condition which causes a processor to enter a speculative-execution mode, the system performs a checkpoint and begins executing instructions in a speculative-execution mode. Upon encountering a branch instruction during speculative-execution mode, the system selects the subsequent instruction to be executed based on a current state of a branch predictor and does not update the current state of the branch predictor, thereby preventing the branch predictor from being incorrectly updated twice when re-executing the branch instruction after returning to normal-execution mode.

In a branch predictor in a processor capable of executing transactional memory transactions, the branch predictor for speculatively prediction outcome of branch instructions, such as taken / not-taken, target address and target instruction. Branch prediction information is buffered during a transaction, and is only loaded into the branch predictor when the transaction is completed, but discarded if the transaction aborts.