Data processing device with branch prediction mechanism
AssigneeFujitsu Limited
InventorMasaki Ukai
Life of this patent
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Abstract
Phantom entries of entries in a branch history are completely detected using a flag identifying a phantom and a flag detecting the misalignment between the address of an instruction and an address where a branch has been predicted, which are provided for a queue executing branch instruction and controlling a phantom, and if the entries are not needed, they are erased. If there is an instruction that branches control flow, a phantom entry is intentionally created and instruction pre-fetching is applied to the entry.
Claims7
(canceled)
A data processing device with a branch prediction mechanism, comprising:
- a queue unit decoding an instruction and issuing it for execution;
- a detection unit judging whether an instruction for where a branch has been predicted falls on a boundary of an instruction word stored in the queue unit when the branch has been predicted for the instruction stored in the queue unit;
- and
- a misalignment erasure unit erasing a branch prediction entry to be stored in the branch prediction mechanism on which the branch prediction is based, if it is judged that the instruction for which where a branch has been predicted does not fall on a boundary of an instruction word.
4-5. (canceled)
A method for erasing an unnecessary entry of branch prediction entries in a data processing device with a branch prediction mechanism, comprising:
- decoding an instruction and issuing it for execution;
- judging whether a target instruction falls on a boundary of the instruction word stored in the queue step when a branch is predicted for the instruction stored in the decoding and issuing step;
- and
- erasing a branch prediction entry to be stored in a branch prediction mechanism on which the branch prediction is based, if it is judged that the target instruction does not fall on a boundary of an instruction word.
(canceled)
Dependencies are inferred from the claim text.