Vector Register Rearrangement via Instruction Grouping
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Solution Overview
Problem
Current data processing systems face performance issues when performing vector load and store instructions that require rearrangement of data elements between memory and vector registers, leading to stalls and inefficiencies, especially in processors that allow overlapped execution of memory and arithmetic operations.
Innovation Solution
The implementation of a group of rearrangement instructions that collectively perform the rearrangement operation, allowing each instruction to access different data elements and vector registers, thereby distributing the computational burden and improving memory subsystem efficiency, and enabling overlapped execution with arithmetic operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single vector load or store instruction performs rearrangement of data elements between memory and vector registers, then the rearrangement operation is completed in one instruction, but the instruction causes memory-related stalls that reduce processor performance
Solution Approach 1:
The patent divides a single vector load/store instruction with rearrangement into multiple separate instructions. Each instruction handles a subset of data elements, allowing the total rearrangement operation to be completed through multiple smaller steps rather than one large instruction, thereby reducing stall impact on overall throughput
Solution Approach 2:
The patent performs partial rearrangement operations in each instruction rather than completing the full rearrangement in a single instruction. By performing rearrangement on subsets of data elements across multiple instructions, the system reduces the stall time per instruction while maintaining the complete rearrangement functionality
2Productivity
If memory and arithmetic operations are overlapped for improved performance, then arithmetic operations can execute during memory operations, but memory-related stalls still represent missed opportunities and reduce overall efficiency
Solution Approach 1:
By segmenting the vector load/store operation into multiple instructions, the patent creates more granular execution units that can be better scheduled and overlapped with arithmetic operations. Each smaller instruction can be issued and executed more frequently, providing more opportunities for overlap with arithmetic operations and reducing the impact of memory stalls
Solution Approach 2:
The patent enables dynamic scheduling of multiple rearrangement instructions to overlap with arithmetic operations in the instruction stream. By having multiple instructions available rather than one large instruction, the processor can dynamically interleave memory and arithmetic operations to maximize parallel execution and minimize idle cycles
Data Source
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AI summary
An apparatus and method are provided for performing a vector rearrangement operation as data elements are moved between memory and vector registers. The apparatus has processing circuitry for performing operations specified by a sequence of program instructions, and a set of vector registers, where each vector register is arranged to store a vector comprising a plurality of data elements. The processing circuitry includes access circuitry to move the data elements between memory and multiple vector registers of the set, and to perform a rearrangement operation as the data elements are moved so that the data elements are arranged in a first organisation in the memory and are arranged in a second, different, organisation in the vector registers. Decode circuitry is arranged to be responsive to a group of rearrangement instructions within the sequence of program instructions to produce control signals to control execution of each rearrangement instruction by the processing circuitry. Each rearrangement instruction in the group defines a data element access pattern that differs to the data element access pattern defined by each other rearrangement instruction in the group, and that causes the access circuitry to access more than one vector register amongst the multiple vector registers involved in the rearrangement operation. Through such an approach, the access circuitry performs the rearrangement operation as a result of the processing circuitry executing all of the rearrangement instructions in the group. The use of such a group of rearrangement instructions can enable an efficient performance of the rearrangement operation by reducing stalling within the apparatus that might otherwise occur if all of the required steps to be performed to implement the rearrangement operation were implemented in response to execution of a single instruction.