Vector Instruction Hazard Tracking for Lower-Latency Execution
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Solution Overview
Problem
Existing vector processing units face latency and power consumption issues due to the need for instructions to wait for previous instructions to finish updating registers, especially when dealing with vector instructions that read and write to multiple registers, leading to inefficient execution.
Innovation Solution
Implementing control storage to track hazarding information for instructions, allowing instructions to check for hazards before execution, reducing the need for costly calculations by pre-calculating and storing hazard information at the vector processing unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If instructions wait for previous instructions to finish executing and updating registers, then data correctness is ensured, but execution latency increases
Solution Approach 1:
The patent pre-calculates and stores hazard information in control storage when instructions are received, before execution begins. This allows the instruction to know in advance whether it needs to wait for previous instructions, eliminating unnecessary waiting while ensuring data correctness only when needed.
Solution Approach 2:
The patent introduces control storage as an intermediary structure that tracks hazard information between instructions. This mediator stores the necessary dependency information, allowing instructions to make informed decisions about execution timing without actually waiting for register updates, thus reducing latency while maintaining correctness.
2Reliability
If instructions check for hazards by detecting writing instructions and calculating hazards at execution time, then data correctness is maintained, but processing time and power consumption increase
Solution Approach 1:
The patent performs hazard detection and information storage as a preliminary action when instructions are received, rather than performing costly hazard calculations at execution time. This shifts the computational workload to an earlier stage when less processing power is required, reducing overall energy consumption while maintaining correctness.
Solution Approach 2:
The patent creates a simplified copy of hazard information in control storage rather than performing complex real-time hazard detection for every instruction. This copied hazard information allows fast execution-time decisions without the computational overhead of full hazard analysis, reducing power consumption while preserving data correctness.
3Adaptability or versatility
If vector instructions read and write to multiple registers, then computational capability is improved, but hazard detection complexity increases
Solution Approach 1:
The patent segments the hazard detection process into two parts: (1) pre-calculating hazard information when instructions are received and storing it in control storage, and (2) simple execution-time checks using the pre-stored information. This segmentation reduces the complexity of real-time hazard detection while maintaining the ability to handle multiple register operations.
Solution Approach 2:
The patent introduces control storage as an intermediary that simplifies hazard detection for multi-register operations. Instead of complex real-time analysis, the system uses the pre-stored hazard information in control storage to make simple lookup decisions, reducing detection complexity while preserving full computational capability for multi-register vector instructions.
Data Source
AI summary
When an instruction is received, the instruction checks against older “in-flight” instructions for hazards, and stores a hazard flag in a control storage entry. An instruction will not start executing while the hazard flag is set. When the older instruction executes and produces a result to a register, it clears the hazard for the current instruction. The current instruction can start executing when no hazards remain.