Inter-Pipeline Hazard Tracking With Compile-Time Counters
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Solution Overview
Problem
In parallel processing units with multiple instruction pipelines, inter-pipeline data hazards are challenging to track and eliminate, leading to inefficiencies and performance issues, as existing hardware-based solutions are costly and complex.
Innovation Solution
A software-controlled method identifies inter-pipeline data hazards at compile time, using counters to link primary and secondary instructions and enforce appropriate ordering, with queues and monitor logic to stall or reschedule instructions as necessary to resolve hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardware-based solutions are used to track and eliminate inter-pipeline data hazards, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex hardware-based hazard tracking mechanisms with a software-controlled approach. The compiler generates metadata tags that identify primary and secondary instructions and their hazard relationships, which are then processed by control logic that adjusts counter values rather than requiring extensive hardware monitoring circuits. This substitution of hardware mechanisms with software-controlled logic reduces hardware complexity while maintaining reliability.
Solution Approach 2:
The patent introduces counters as intermediary elements that mediate between the instruction pipelines and hazard tracking. Each primary instruction has an associated counter that tracks the number of unresolved hazards. These counters serve as intermediaries that simplify the tracking mechanism by providing a single-value state representation instead of requiring complex hardware circuits to monitor multiple instruction dependencies across pipelines.
2Device complexity
If software-controlled hazard tracking is implemented, then device complexity is reduced, but processing speed may be affected
Solution Approach 1:
The patent performs hazard identification and metadata generation during the compile time phase, before runtime execution. The compiler analyzes instruction sequences, identifies primary and secondary instructions with hazard relationships, and embeds this information in metadata tags. This preliminary action moves the complex hazard analysis work from runtime to compile time, allowing faster runtime execution with minimal overhead.
Solution Approach 2:
The patent maintains continuous instruction flow through the pipelines by using counters that can be quickly adjusted without stalling entire pipeline stages. When a primary instruction is output, its counter is incremented; when hazards are resolved, the counter is decremented. This allows secondary instructions to proceed as long as their associated counters indicate no unresolved hazards, maintaining continuous useful action rather than forcing sequential waiting.
3Productivity
If inter-pipeline data hazards are tracked and eliminated, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent segments the hazard tracking mechanism into separate, independent counter elements for each primary instruction. Instead of requiring a monolithic hazard tracking system that monitors all instructions across all pipelines, the system divides tracking into discrete counter units that can be independently managed. Each counter tracks hazards for its associated primary instruction, allowing modular and scalable implementation that supports parallel processing without proportionally increasing overall system complexity.
Data Source
AI summary
Data hazards are avoided by stalling from execution a received secondary instruction determined to be dependent on a primary instruction by an associated instruction pipeline if a counter of a plurality of counters associated with the primary instruction indicates that there is a hazard related to the primary instruction. In response to detecting that a hazard related to a primary instruction has been resolved by an instruction pipeline of a plurality of instruction pipelines, an adjustment signal is transmitted to a counter block that causes the value of the counter of the plurality of counters of the counter block associated with the primary instruction to be adjusted to indicate that the hazard related to the primary instruction has been resolved.