Vector Execution Circuitry Address Hazard Detection
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Solution Overview
Problem
Existing vector operation techniques face challenges in managing address collisions, leading to performance bottlenecks due to unpredictable address conflicts, which often result in conservative compilation approaches and missed performance gains.
Innovation Solution
An apparatus and method that dynamically check for address hazards during vector loop iterations, allowing for adaptive vectorization by employing a default level of vectorization when no hazards are present and reducing it when hazards are detected, using a check instruction to influence the control flow and execute a fallback path of instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If code is vectorised to improve performance, then processing speed increases, but address conflicts may occur causing incorrect results
Solution Approach 1:
The patent performs address conflict detection before executing vector operations by checking whether memory addresses accessed by different lanes of a vector operation are unique. This preliminary check prevents incorrect results by identifying potential address conflicts before they occur, allowing the system to either adjust the vector operation or proceed safely with full vectorisation.
2Reliability
If address conflict detection mechanisms are introduced to ensure correctness, then reliability improves, but latency increases limiting performance benefits
Solution Approach 1:
The patent segments the address conflict detection process into distinct stages: generating memory addresses for each lane, checking for uniqueness, and then deciding on the vector operation execution. This segmentation allows the system to perform detection efficiently in parallel where possible and only serialize critical path operations, reducing overall latency while maintaining correctness.
Solution Approach 2:
The patent introduces an intermediary address conflict detection mechanism that sits between the vector operation generation and execution. This intermediary layer checks addresses and provides guidance on whether to proceed with full vectorisation, scalar conversion, or adjusted vectorisation, thereby enabling fast detection without compromising correctness.
3Reliability
If conservative compilation approach is used to avoid address conflicts, then correctness is maintained, but performance gains from vectorisation are lost
Solution Approach 1:
The patent dynamically adjusts the vectorisation strategy based on runtime address conflict detection results. Instead of using a static conservative approach, the system can switch between full vectorisation, adjusted vectorisation with modified lane counts, or scalar execution on a per-vector-operation basis, thereby maximizing performance while ensuring correctness through adaptive decision-making.
Data Source
AI summary
Address collisions are managed when performing vector operations. A register store stores vector operands. Execution circuitry performs memory access operations to move the vector operands between the register store and memory and data processing operations using the vector operands. The execution circuitry may iteratively execute a vector loop, where during each iteration the execution circuitry executes a sequence of instructions to implement the vector loop. The sequence includes a check instruction identifying a plurality of memory addresses. The execution circuitry responds to the check instruction to determine whether an address hazard condition exists among the plurality of memory addresses. For each iteration of the vector loop, the execution circuitry responds to the check instruction determining an absence of the hazard address condition to employ a default level of vectorization when executing the sequence of instructions to implement the vector loop. But in the presence of the address hazard condition, the execution circuitry employs a reduced level of vectorization to implement the vector loop.