Register Renaming Circuitry for Faster Physical Register Release
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Solution Overview
Problem
In data processing, register renaming techniques face challenges in efficiently managing physical registers due to complex conditions for freeing renamed registers, leading to prolonged unavailability and potential errors from out-of-order execution and speculative execution.
Innovation Solution
Implementing a register renaming circuitry that differentiates between architectural and additional registers, using a second set of less restrictive conditions for freeing additional registers, which allows quicker release by counting micro-operations or clock cycles, and employing a counter to determine when micro-operations have completed, thereby simplifying the monitoring of register availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex conditions are applied to ensure correct register freeing in speculative execution, then reliability is improved, but device complexity and loss of time increase
Solution Approach 1:
The patent segments the register set into two distinct categories: architectural registers and additional registers. This segmentation allows different freeing conditions to be applied to each type, simplifying the overall system while maintaining reliability. Architectural registers use conservative multi-condition checking, while additional registers use simpler counter-based tracking.
Solution Approach 2:
Different freeing conditions are applied locally to different register types based on their specific characteristics. Architectural registers require comprehensive validation (write completion, renaming table removal, exception table checking), while additional registers use simpler micro-operation counting. This localized approach optimizes each register type's freeing process.
2Reliability
If conservative conditions are used for freeing architectural registers, then reliability is improved, but loss of time increases
Solution Approach 1:
The patent divides registers into architectural and additional categories, allowing conservative multi-condition checking for architectural registers while using faster counter-based tracking for additional registers. This segmentation enables parallel processing of register freeing decisions with different validation depths.
Solution Approach 2:
For additional registers, the patent applies a sufficient but not excessive validation approach using micro-operation counters. Instead of checking all possible conditions, it counts the number of micro-operations to determine when a register is safe to free, which is adequate for correctness but faster than comprehensive checking.
3Reliability
If monitoring of processor state is performed to determine register availability, then reliability is improved, but device complexity and loss of time increase
Solution Approach 1:
The patent extracts the monitoring function into a dedicated counter mechanism that operates independently for additional registers. Instead of having the main processor state monitoring system track every additional register, a separate simple counter is used that only counts micro-operations, reducing the burden on the main monitoring system.
Solution Approach 2:
The patent uses a simplified copy of the validation logic for additional registers - instead of implementing the full architectural register freeing logic, it uses a micro-operation counter that replicates the essential functionality (tracking when registers become available) without the complexity of full state monitoring.
Data Source
AI summary
Register renaming circuitry for a processing apparatus configured to process a stream of instructions from an instruction set specifying registers from an architectural set of registers. The apparatus including a physical set of registers configured to store data values being processed by the processing apparatus. Register renaming circuitry is configured to receive a stream of operations from an instruction decoder and to map registers that are to be written to by the stream of operations to physical registers within the physical set of registers that are currently available. The register renaming circuitry comprises register release circuitry configured to release the physical registers that have been mapped to the registers when a first set of conditions have been met, and to release the physical registers that have been mapped to the additional registers when a second set of conditions have been met.