Stack Pointer Load-Store Dependence Predictor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current computing systems face inefficiencies in reducing latency and power consumption during memory access operations, particularly due to data dependencies that hinder processor throughput, such as RAW dependencies between load and store instructions.
Innovation Solution
The implementation of a stack pointer load-store dependence (SP-LSD) predictor and a register file (RF-LSD) predictor, which use tables and control logic to predict memory dependencies and perform register renaming, thereby reducing latency by anticipating and managing dependencies between stack push and pop operations and other memory instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If register renaming is used to handle WAR and WAW dependencies, then parallel execution of instructions is enabled, but true RAW dependencies still cause serialization of instruction execution
Solution Approach 1:
The patent performs register renaming in the decode stage, which is earlier than the traditional rename stage. This preliminary action allows the processor to identify and handle RAW dependencies between stack push and pop instructions before they reach the execution stage, enabling earlier detection of opportunities to eliminate serialization and improve instruction throughput.
2Loss of time
If memory dependence prediction is implemented, then latency of load operations is reduced, but device complexity increases due to additional predictor hardware
Solution Approach 1:
The patent divides memory dependence prediction into two separate predictors: the SP-LSD predictor specifically for stack push-pop dependencies and the RF-LSD predictor for general load-store dependencies. This segmentation allows each predictor to be optimized for its specific purpose, reducing the overall complexity compared to a single comprehensive predictor while maintaining effective latency reduction.
Solution Approach 2:
The patent creates specialized predictor structures with different characteristics for different types of memory dependencies. The SP-LSD predictor uses stack pointer information and specific table structures optimized for push-pop sequences, while the RF-LSD predictor handles general register file dependencies. This local optimization allows each predictor to efficiently handle its specific case without requiring complex general-purpose logic.
3Productivity
If speculative execution is used to handle memory dependencies, then processor throughput is maintained, but power consumption increases
Solution Approach 1:
The patent performs register renaming and memory dependence prediction in the decode stage, which is earlier in the pipeline than traditional approaches. This preliminary action allows the processor to identify and resolve dependencies before instructions are dispatched for execution, reducing the need for later speculative execution and its associated power consumption while maintaining throughput.
Data Source
AI summary
A system and method for efficiently reducing the latency and power of memory access operations. A processor includes a stack pointer (SP) load-store dependence (LSD) predictor which predicts whether a memory dependence exists on a store instruction. The processor also includes a register file (RF) LSD predictor which predicts whether a memory dependence exists on a store instruction or a load instruction by a subsequent load instruction in program order. Each of the SP-LSD predictor and the RF-LSD predictor predicts and performs register renaming in a pipeline stage earlier than a renaming pipeline stage. The RF-LSD predictor also determines whether any intervening instructions between a producer memory instruction and a consumer memory instruction modify a predicted dependence.