Prediction Circuitry for Register Renaming Sector Selection
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Solution Overview
Problem
Delays in execution of instruction sequences occur due to stalled instructions waiting for functional units or dependencies, despite register renaming techniques, which can hinder parallelism and performance in data processing.
Innovation Solution
A data processing apparatus with prediction circuitry that learns sector identifiers and delay indicators from performance monitoring information to optimize register renaming, mapping architectural registers to physical registers, and scheduling subsequent instructions based on predicted performance metrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If register renaming is used to remove dependencies, then parallelism is improved, but execution delays still occur due to stalled instructions waiting for functional units
Solution Approach 1:
The prediction circuitry performs preliminary actions by predicting sector identifiers and delay indicators before instruction execution completes. The prediction is made based on performance monitoring information from previous instruction sequences, allowing the register rename circuitry to pre-determine optimal physical register mappings and scheduling delays, thus reducing execution delays while maintaining parallelism benefits
Solution Approach 2:
The system implements feedback through performance monitoring information that tracks execution performance for sequences of instructions using different sector identifiers. This feedback is fed back to the prediction circuitry, which uses it to refine future predictions, creating a closed-loop system that continuously optimizes register renaming and instruction scheduling to minimize execution delays
2Speed
If physical register array is divided into multiple sectors with different access properties, then register access performance is improved, but device complexity increases
Solution Approach 1:
The physical register array is divided into multiple sectors, each with different access properties tailored to specific needs. The prediction circuitry learns which sectors provide optimal access performance for different instruction sequences, allowing the system to assign appropriate sectors to different registers based on their access patterns, thus improving overall access performance while managing the complexity through intelligent allocation
3Productivity
If prediction circuitry uses performance monitoring information to select sector identifiers, then register utilization is improved, but measurement and detection complexity increases
Solution Approach 1:
The system performs self-service by using its own execution results and performance data to train the prediction circuitry. The performance monitoring information is generated from actual instruction execution, and this same data is used to refine predictions, creating a self-improving system that automatically optimizes register utilization without requiring external intervention or complex external measurement systems
Data Source
AI summary
A data processing apparatus comprises: a physical register array, prediction circuitry, register rename circuitry, and hardware execution circuitry. The physical register array comprises a plurality of sectors having one or more different access properties, each of the plurality of sectors having one or more different access properties compared to other sectors of the plurality of sectors, each sector of the plurality of sectors comprising at least one physical register. The prediction circuitry to predict, for a given instruction, a sector identifier identifying one of the sectors of the physical register array to be used for a destination register of the given instruction. The prediction circuitry is configured to select the sector identifier in dependence on prediction information learnt from performance monitoring information indicative of performance achieved for a sequence of instructions when using different sector identifiers for the given instruction. The register rename circuitry to map a destination architectural register identifier specified by the given instruction to a destination physical register in the sector identified by the sector identifier predicted by the prediction circuitry. The execution circuitry to execute the given instruction and generate a result to be written to the destination physical register mapped to the destination architectural register identifier by the register rename circuitry.