Sticky Bit Segmentation for Speculative Execution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing data processing systems that support speculative execution face resource overhead issues due to the need for large numbers of registers for register renaming and excessive storage requirements when combining with sticky bits, which restrict speculation and increase resource consumption.
Innovation Solution
Implementing sticky bit storage circuitry to store separate versions of sticky bits associated with segments of program instructions, allowing speculative execution to proceed while minimizing storage needs and enabling state restoration without the need for extensive register allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If register renaming is used to support speculative execution, then instruction execution throughput is improved, but the number of registers required increases significantly
Solution Approach 1:
The patent divides the program instructions into segments separated by speculation nodes. Each segment can be executed speculatively with its own sticky bit version, allowing register renaming to be applied selectively within segments rather than requiring separate registers for every possible speculative outcome across the entire program.
Solution Approach 2:
The patent changes the state parameter of sticky bits by creating separate versions for different segments. This allows the system to track exception conditions across speculative boundaries without requiring full register renaming, as the sticky bit versions can be restored or discarded based on speculation outcomes.
2Reliability
If separate sticky bit versions are stored for each event and instruction, then state restoration capability is improved, but storage requirements increase significantly
Solution Approach 1:
The patent segments the program into regions separated by speculation nodes and creates sticky bit versions at these boundaries. This segmentation approach provides state restoration capability only where needed (at speculation nodes) rather than maintaining separate sticky bit versions for every instruction, significantly reducing storage requirements while preserving reliability.
Solution Approach 2:
The patent applies partial action by creating sticky bit versions only at speculation nodes rather than for every instruction. This provides sufficient state restoration capability for speculative execution needs without the excessive storage overhead of maintaining versions for all possible event outcomes at every instruction point.
3Device complexity
If speculation is restricted beyond events that update sticky bits, then register renaming overhead is reduced, but the amount of speculation that can be performed is limited
Solution Approach 1:
The patent introduces speculation nodes that segment the program into regions. Speculation is permitted within these segments even beyond sticky bit updating events, while speculation boundaries are clearly defined at the nodes. This segmentation allows flexible speculation capability within segments while maintaining manageable complexity through structured boundaries.
Data Source
AI summary
A data processing apparatus 2 supports speculative execution and the use of sticky bits. A different version of a sticky bit is associated with each segment of the speculative program flow. The segments of the program flow are separated by speculation nodes corresponding to program instructions which may be followed by a plurality of different alternative program instruction serving as the next program instruction. When a speculation node is resolved, then the segments separated by that speculation node are merged and the sticky bit values for those two segments are merged.