Register Renamer Even Odd Banks False Dependency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Implementing register renaming in processors that define multiple aliases for the same storage location is complex, leading to challenges in detecting and resolving false dependencies between instructions, which affects execution performance and parallelism.
Innovation Solution
A processor with a register renamer organized into even and odd banks, where each entry stores a physical register identifier, allowing for efficient mapping and renaming of architected registers of varying sizes by selecting appropriate banks based on the register number bits, and handling false dependencies by creating aliases that decode to the same renamer entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If register renaming is implemented to eliminate false dependencies and improve execution performance, then code parallelism and throughput are improved, but the complexity of the register renamer increases significantly when handling multiple register size aliases
Solution Approach 1:
The register renamer is segmented into multiple banks (even and odd banks) where each bank handles specific register size aliases. This segmentation allows the system to manage complexity by dividing the renaming task across separate storage structures, each optimized for particular register sizes, rather than using a single complex renaming structure.
Solution Approach 2:
The patent introduces an intermediary mapping structure that translates between different register size aliases and a unified physical register namespace. This intermediary layer handles the complexity of multiple aliases by providing a standardized interface, allowing the register renamer to manage diverse register sizes without requiring separate renaming logic for each size.
2Adaptability or versatility
If multiple aliases for the same storage location are supported, then versatility and adaptability of the register file are improved, but false dependency detection becomes more difficult and error-prone
Solution Approach 1:
The patent creates copy relationships between alias entries in the register renamer, where multiple alias entries point to the same underlying physical register mapping. This copying mechanism allows the system to support multiple aliases while maintaining consistent dependency tracking, as all aliases referencing the same storage location share the same renamer entry and thus the same dependency information.
Solution Approach 2:
The register renamer implements feedback mechanisms that track and propagate dependency information across all aliases of a given storage location. When a rename operation occurs on one alias, the dependency information is fed back to update all related aliases, ensuring consistent false dependency detection across the entire alias family.
Data Source
AI summary
A processor may include a physical register file and a register renamer. The register renamer may be organized into even and odd banks of entries, where each entry stores an identifier of a physical register. The register renamer may be indexed by a register number of an architected register, such that the renamer maps a particular architected register to a corresponding physical register. Individual entries of the renamer may correspond to architected register aliases of a given size. Renaming aliases that are larger than the given size may involve accessing multiple entries of the renamer, while renaming aliases that are smaller than the given size may involve accessing a single renamer entry.