Method and system for preventing livelock due to competing updates of prediction information
AssigneeInternational Business Machines Corporation
InventorsERIK R. ALTMAN, Vijayalakshmi Srinivasan
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Abstract
A system to prevent livelock. An outcome of an event is predicted to form an event outcome prediction. The event outcome prediction is compared with a correct value for a datum to be accessed. An instruction is appended with a real event outcome when the outcome of the event is mispredicted to form an appended instruction. A prediction override bit is set on the appended instruction. Then, the appended instruction is executed with the real event outcome.
Claims20
A computer implemented method in a data processing system to prevent livelock, the computer implemented method comprising:
- predicting an outcome of an event to form an event outcome prediction;
- comparing the event outcome prediction with a correct value for a datum to be accessed;
- appending to an instruction a real event outcome when the outcome of the event is mispredicted to form an appended instruction;
- setting a prediction override bit on the appended instruction;
- and
- executing the appended instruction with the real event outcome.
The computer implemented method of claim 6, wherein the load instruction includes source operands, and wherein the source operands provides the effective address of the datum to be accessed.
A data processing system to prevent livelock, comprising:
- a bus system;
- a storage device connected to the bus system, wherein the storage device includes a set of instructions;
- and
- a processing unit connected to the bus system, wherein the processing unit executes the set of instructions to predict an outcome of an event to form an event outcome prediction, compare the event outcome prediction with a correct value for a datum to be accessed, append to an instruction a real event outcome when the outcome of the event is mispredicted to form an appended instruction, set a prediction override bit on the appended instruction, and execute the appended instruction with the real event outcome.
A computer program product to prevent livelock, the computer program product comprising:
- a computer usable medium having computer usable program code embodied therein, the computer usable medium comprising:
- computer usable program code configured to predict an outcome of an event to form an event outcome prediction;
- computer usable program code configured to compare the event outcome prediction with a correct value for a datum to be accessed;
- computer usable program code configured to append to an instruction a real event outcome when the outcome of the event is mispredicted to form an appended instruction;
- computer usable program code configured to set a prediction override bit on the appended instruction;
- and
- computer usable program code configured to execute the appended instruction with the real event outcome.
Dependencies are inferred from the claim text.