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US 8,078,853 B1Granted
Explicit control of speculation
OwnerH. Peter Anvin, David Dunninventors
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Abstract
Described are methods and systems that allow partial speculation (e.g., speculation within constraints). With partial speculation, after a fault is detected for example, speculation remains enabled for processor registers and other memories private to a microprocessor, while speculation normally permitted for certain other operations is suspended. Accordingly, while the fault is dispatched, some speculation is permitted as opposed to suspending all speculation. As such, microcode that makes use of speculation can be written.
Claims26
A method comprising:
- operating a computer system in a first mode of speculative operation, said first mode permitting speculation of a first set of speculative operations;
- in response to an event during said operating, restoring a state of a microprocessor to a state stored prior to said event;
- and
- subsequent to said restoring, exiting said first mode and entering a partial speculation mode, wherein said partial speculation mode permits speculation of a second set of speculative operations comprising some but not all of said first set.
1 more element
A method comprising:
- executing instructions after a point in time at which a first memory state for a microprocessor is stored, said executing according to a full speculation mode that permits a set of speculative operations;
- in response to an event during said executing, restoring said microprocessor to said first memory state;
- subsequent to said restoring, executing instructions according to a partial speculation mode, wherein in said partial speculation mode some but not all of said set of speculative operations are suspended.
A computer system comprising:
- a main memory;
- and
- a microprocessor coupled to said main memory;
- wherein said computer system is operable for implementing a first mode of speculative operation in which a set of speculative operations are permitted, a second mode of partial speculative operation in which some but not all of said set of speculative operations are permitted, and a third mode in which all of said first set of speculative operations are suspended, wherein said computer system is operable for selecting said second mode following an operation that causes a state of said microprocessor to be restored to a prior state.
1 more element
Dependencies are inferred from the claim text.