Load Address Prediction Engine Using Path History
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Solution Overview
Problem
Conventional processor optimizations for load instructions, such as data prefetching and data value prediction, while improving performance, still face challenges in reducing execution latency due to variability in data access times across the memory hierarchy, necessitating further mechanisms to enhance processor efficiency.
Innovation Solution
A load address prediction engine using address prediction tables based on load path history is introduced, which generates a table index and predictor tag for load instructions to predict memory addresses, facilitating data value prediction, prefetching, and memory disambiguation, and includes confidence values and cache way indicators to optimize cache access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If data prefetching and data value prediction are used to speed up load instructions, then execution latency is reduced, but the variability in data access times across the memory hierarchy remains, impacting load-dependent instructions
Solution Approach 1:
The patent applies preliminary action by using address prediction tables to predict memory addresses before actual data access occurs. The prediction engine analyzes load path history and generates predicted addresses in advance, allowing the system to prepare for data access patterns before they actually happen, thereby reducing execution latency while maintaining reliable access timing through consistent prediction accuracy.
2Productivity
If conventional processor optimizations are applied to load instructions, then performance is improved, but execution latency variability persists due to memory hierarchy depth variations
Solution Approach 1:
The patent implements feedback mechanisms where the address prediction engine continuously learns from actual load access patterns and updates its predictions accordingly. By analyzing the feedback from actual data access outcomes, the system refines its prediction accuracy over time, maintaining high processor performance while reducing latency variability through adaptive prediction improvements.
3Measurement precision
If address prediction tables with multiple entries are used to improve prediction accuracy, then load address prediction precision increases, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the address prediction function into multiple independent table entries, each handling specific load path history patterns. Instead of using a single complex prediction mechanism, the system segments the prediction space into multiple simpler entries that can be independently managed and updated, achieving high prediction accuracy while keeping individual table entry complexity low.
Data Source
AI summary
Aspects disclosed in the detailed description include providing load address predictions using address prediction tables based on load path history in processor-based systems. In one aspect, a load address prediction engine provides a load address prediction table containing multiple load address prediction table entries. Each load address prediction table entry includes a predictor tag field and a memory address field for a load instruction. The load address prediction engine generates a table index and a predictor tag based on an identifier and a load path history for a detected load instruction. The table index is used to look up a corresponding load address prediction table entry. If the predictor tag matches the predictor tag field of the load address prediction table entry corresponding to the table index, the memory address field of the load address prediction table entry is provided as a predicted memory address for the load instruction.