Instruction Cache Branch Rearrangement for Execution Efficiency
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Solution Overview
Problem
Branching instructions in instruction caches lead to inefficiencies due to frequent jumps to remote addresses, which can result in decreased code execution efficiency, especially when data needs to be discarded or retrieved from memory.
Innovation Solution
A method that identifies and rearranges branching instructions in the instruction cache based on historical data to prioritize 'hot' targets over 'cold' targets, inserting jump instructions and duplicating code blocks to optimize the execution path, thereby reducing the number of jumps to remote addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If branching instructions jump to remote targets in the instruction cache, then code flexibility is improved, but code execution efficiency deteriorates
Solution Approach 1:
The system performs preliminary analysis of branch prediction accuracy and proactively reorganizes instruction cache layout before execution. By identifying frequently taken branches and their targets in advance, the system pre-positions instructions to minimize cache jumps, thereby improving execution efficiency while preserving code flexibility through conditional branching.
Solution Approach 2:
The instruction cache organization is made dynamic by adjusting the layout based on runtime branch prediction data. The system continuously monitors branch behavior and reorganizes the cache to place hot targets near their branch instructions, creating an adaptive structure that optimizes for actual execution patterns rather than static predetermined layouts.
2Speed
If instructions are pre-cached in the instruction cache, then code execution speed is improved, but data management complexity increases when remote jumps are required
Solution Approach 1:
The system introduces an intermediary layer of branch prediction analysis and cache reorganization logic that mediates between pre-cached instructions and remote jump requirements. This intermediary mechanism analyzes branch patterns and strategically positions instructions in the cache to reduce the frequency and impact of remote jumps, thereby maintaining execution speed while simplifying data management.
3Ease of operation
If the instruction cache maintains a linear layout, then cache access simplicity is improved, but branch target accessibility deteriorates
Solution Approach 1:
The instruction cache is segmented into regions based on branch prediction hotspots. Frequently taken branch targets are positioned in optimized locations close to their source instructions, while less critical instructions maintain linear placement. This segmentation allows the system to preserve overall cache access simplicity while dramatically improving branch target accessibility through strategic local repositioning.
Data Source
AI summary
Instruction cache behavior and branch prediction are used to improve the functionality of a computing device by profiling branching instructions in an instruction cache to identify likelihoods of proceeding to a plurality of targets from the branching instructions; identifying a hot path in the instruction cache based on the identified likelihoods; and rearranging the plurality of targets relative to one another and associated branching instructions so that a first branching instruction that has a higher likelihood of proceeding to a first hot target than to a first cold target and that previously flowed to the first cold target and jumped to the first hot target instead flows to the first hot target and jumps to the first cold target.