Prediction Circuitry Deactivation for Control-Flow Power Reduction
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Solution Overview
Problem
Prediction circuitry for control flow instructions is power intensive and can be inefficient when the contents of local and global history storage circuits are similar, leading to redundant predictions.
Innovation Solution
Implementing power control circuitry to disable prediction circuitry when the subset of control flow information stored in local history storage matches the global history storage, using techniques such as TAGE predictors and local history registers to reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prediction circuitry is continuously enabled to produce control flow predictions, then prediction accuracy is maintained, but power consumption increases
Solution Approach 1:
The prediction circuitry transitions between enabled and disabled states dynamically based on the similarity determination between local and global history storage contents. The power control circuitry enables the prediction circuitry only when the local history storage contains significantly different information from the global history storage, otherwise it disables the prediction circuitry to save power while maintaining prediction accuracy when needed.
2Use of energy by moving object
If prediction circuitry is disabled to save power, then power consumption decreases, but prediction accuracy may be compromised
Solution Approach 1:
The power control circuitry continuously monitors and determines the similarity between the subset of control flow information in local history storage and the control flow information in global history storage. Based on this feedback comparison, it intelligently controls the enablement state of the prediction circuitry, ensuring that the prediction circuitry is enabled only when the local history provides significantly different and potentially more accurate prediction information.
3Reliability
If local history storage is maintained separately to improve prediction accuracy, then prediction quality improves, but device complexity increases
Solution Approach 1:
The power control circuitry merges the functionality of maintaining separate local and global history storages by determining their similarity and using this information to control the prediction circuitry. This integration allows the system to leverage both local and global history information without requiring permanently active prediction circuitry for both, thereby reducing overall device complexity while maintaining prediction quality.
Data Source
AI summary
A data processing apparatus is provided. It includes first history storage circuitry that stores control flow information of control flow instructions. Second history storage circuitry stores a subset of the control flow information by considering a subset of the control flow instructions. Prediction circuitry produces a prediction for a specific one of the control flow instructions based on the subset of the control flow information and power control circuitry performs a determination of an extent to which the subset of the control flow information matches the control flow information and disables the prediction circuitry in dependence on a result of the determination.