US 10,761,844 B2 · Systems and methods to predict load data values

Abstract

Disclosed embodiments relate to predicting load data. In one example, a processor a pipeline having stages ordered as fetch, decode, allocate, write back, and commit, a training table to store an address, predicted data, a state, and a count of instances of unchanged return data, and tracking circuitry to determine, during one or more of the allocate and decode stages, whether a training table entry has a first state and matches a fetched first load instruction, and, if so, using the data predicted by the entry during the execute stage, the tracking circuitry further to update the training table during or after the write back stage to set the state of the first load instruction in the training table to the first state when the count reaches a first threshold.

Claims25

Dependent claims

A processor comprising:

fetch and decode circuitry to fetch and decode load instructions;
a training table to store, for each of a plurality of load instructions, an address, predicted data, a state, and a count of instances of unchanged return data;
and
tracking circuitry to determine, during one or more of allocate and decode stages, whether a training table entry has a first state and matches a fetched first load instruction, and, if so, using the data predicted by the entry during an execute stage, the tracking circuitry further to update the training table during or after a write back stage to:
when no match exists, add a new entry reflecting the first load instruction,
when a match exists, but has different predicted data than data returned for the first load instruction, reset the count and set the state to a second state, and
when a match exists with matching predicted data, increment the count and, when the incremented count reaches a first threshold, set the state to the first state.

4 more elements

A method comprising:

storing a first load instruction in a training table comprising, for each entry, an address, predicted data, a state, and a count of instances of unchanged return data;
determining, during one or more of allocate and decode stages, whether a training table entry having a stored address matching that of a fetched first load instruction exists and has a first state, and, if so, using the data predicted by the entry to optimize execution;
and
updating the training table during or after a write back stage by:
when no match exists, adding a new entry reflecting the first load instruction,
when a match exists, but has different predicted data than data returned for the first load instruction, resetting the count and setting the state to a second state, and
when a match exists with matching predicted data, incrementing the count and, when the incremented count reaches a first threshold, setting the state to the first state.

4 more elements

A non-transitory computer-readable medium containing instructions that, when performed by a processor having a pipeline comprising fetch, allocate, decode, write back, and commit stages, are to cause the processor to respond by:

storing a first load instruction in a training table comprising, for each entry, an address, predicted data, a state, and a count of instances of unchanged return data;
determining, during one or more of the allocate and decode stages, whether a training table entry having a stored address matching that of a fetched first load instruction exists and has a first state, and, if so, using the data predicted by the entry to optimize execution;
and
updating the training table during or after the write back stage by:
when no match exists, adding a new entry reflecting the first load instruction,
when a match exists, but has different predicted data than data returned for the first load instruction, resetting the count and setting the state to a second state, and
when a match exists with matching predicted data, incrementing the count and, when the incremented count reaches a first threshold, setting the state to the first state.

4 more elements

Dependencies are inferred from the claim text.

Systems and methods to predict load data values

Life of this patent

Systems and methods to predict load data values

Life of this patent

Abstract

Claims25