ReadXF Instruction Vector Fault Handling
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Solution Overview
Problem
Existing vector processors face challenges in vectorizing loops due to dependencies between iterations, such as loop-carried data dependencies and memory-address aliasing, which limits the extent of parallelism that can be exploited, thereby restricting the performance benefits of vectorization.
Innovation Solution
The processor employs a ReadXF instruction that handles faults by determining if a corresponding element of the control vector is active, allowing it to either process or mask faults, enabling dynamic switching between scalar and vector execution based on runtime conditions, and maintaining a fault-status register to track masked elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the processor performs read operations on all elements of the input vector, then the parallelism and productivity are improved, but the reliability deteriorates due to fault conditions encountered during read operations
Solution Approach 1:
The patent applies partial action by selectively performing read operations only on elements where the control vector indicates active status. This prevents fault conditions on inactive elements while maintaining parallelism on valid elements, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The control vector acts as an intermediary that mediates between the input vector and the read operation. It filters which elements should undergo read operations, preventing fault propagation while enabling parallel execution on valid elements, thus balancing productivity and reliability.
2Productivity
If the processor masks faults for all elements, then the productivity is improved by avoiding fault handling overhead, but the reliability deteriorates by potentially missing critical error conditions
Solution Approach 1:
The patent applies local quality by differentiating fault handling based on the control vector status for each element. Active elements undergo strict fault handling to ensure reliability, while inactive elements have faults masked to maintain productivity, resolving the contradiction between execution speed and error detection.
Solution Approach 2:
The patent applies partial action by masking faults only for inactive elements indicated by the control vector, while maintaining strict fault handling for active elements. This selective approach improves productivity by reducing fault handling overhead on irrelevant elements while preserving reliability on critical elements.
3Productivity
If the processor requires complete vectorization for performance benefits, then the productivity is improved, but the adaptability deteriorates due to dependencies between loop iterations
Solution Approach 1:
The patent applies segmentation by dividing the vector processing into active and inactive segments based on the control vector. This allows independent processing of each segment, enabling partial vectorization on active elements while handling dependencies on inactive elements, thus improving both performance and adaptability.
Solution Approach 2:
The patent applies dynamics by making the vectorization extent dynamic based on runtime control vector values. The processor adapts the degree of parallelism executed based on which elements are active, allowing flexible adjustment between scalar and vector execution modes to resolve the contradiction between performance and adaptability.
Data Source
AI summary
The described embodiments include a processor that handles faults. The processor first receives a first input vector, a control vector, and a predicate vector, each vector comprising a plurality of elements. For each element in the first input vector for which a corresponding element in the control vector and the predicate vector are active, the processor then performs a read operation using an address from the element of the first input vector. When a fault condition is encountered while performing the read operation, the processor determines if the element is a first element where a corresponding element of the control vector is active. If so, the processor handles/processes the fault. Otherwise, the processor masks the fault for the element.