Vector Micro-Operation Dispatch for Non-Blocking Unit Stride Loads
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Solution Overview
Problem
Processor pipelines experience bottlenecks and reduced throughput due to the mix of scalar and vector instructions, particularly when vector instructions are divided into multiple micro-operations, leading to pipeline stalls and inefficient use of CPU resources.
Innovation Solution
Implement non-blocking unit stride vector instruction dispatch by dividing vector operations into micro-operations and routing them through dedicated scalar and vector request queues, using a reorder buffer identifier (ROBID) to ensure proper sequencing and out-of-order execution, thereby reducing the likelihood of pipeline stalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If vector instructions are divided into multiple micro-operations and processed through shared request queues, then vector processing capability is improved, but pipeline stalls increase and throughput decreases
Solution Approach 1:
The patent segments the request queue into separate scalar and vector request queues, allowing independent processing paths. Vector micro-operations are routed through dedicated vector queues rather than competing for shared scalar queue resources, eliminating the bottleneck that caused pipeline stalls while maintaining vector processing capability.
2Device complexity
If scalar and vector instructions are processed in the same pipeline using shared queues, then device complexity is reduced, but pipeline stalls increase due to resource contention
Solution Approach 1:
The request queue is divided into distinct scalar and vector segments (queues), allowing parallel processing without requiring completely separate pipelines. This segmentation reduces resource contention and pipeline stalls while adding minimal complexity compared to fully independent scalar and vector pipelines.
3Speed
If vector operations are executed as single instructions, then instruction execution speed is improved, but resource utilization decreases due to inability to interleave with scalar operations
Solution Approach 1:
By segmenting the request queue and separating scalar and vector micro-operation streams, the patent enables out-of-order execution and interleaving of scalar and vector operations. This maintains high instruction execution speed while improving overall CPU resource utilization through better pipeline occupancy.
Solution Approach 2:
The patent implements dynamic scheduling where vector micro-operations can be executed out of order when scalar operations are pending, and vice versa. This dynamic approach allows the pipeline to adapt to varying workloads and maintain high utilization without sacrificing the speed of individual vector operation execution.
Data Source
AI summary
Disclosed techniques enable vector instruction processing. A processor core is accessed. The processor core is coupled to a memory hierarchy, and is configured to execute vector operations, scalar operations, and micro-operations. A decode unit decodes a vector memory operation. The vector memory operation is associated with a unit stride addressing mode. The decoding includes dividing the vector memory operation into one or more vector memory micro-operations. A dispatch unit sends at least one vector micro-operation within the one or more vector micro-operations to a scalar request queue within a plurality of request queues. The at least one vector micro-operation is issued to a load-store unit within the processor core. The issuing includes selecting, from the plurality of request queues, the at least one vector memory micro-operation.