Processor Data Element Rearrangement Instructions
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Solution Overview
Problem
Current processors lack efficient instructions for data element rearrangement, particularly in SIMD architectures, which can lead to asymmetry and increased costs in implementing certain algorithms, making it difficult to vectorize operations effectively.
Innovation Solution
Incorporating instructions such as gather by indices to register, scatter by indices to register, and data element rearrangement instructions that allow for the rearrangement of indices between scatter and gather patterns, enhancing the processor's ability to perform parallel operations and improve algorithm efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional SIMD architectures are used without dedicated rearrangement instructions, then the processor structure remains simple, but algorithm implementation becomes asymmetric and less efficient
Solution Approach 1:
The data rearrangement operation is segmented into distinct phases: gather phase (collecting scattered data elements into contiguous storage), rearrangement phase (reordering elements within the register), and scatter phase (distributing elements to target locations). This segmentation allows each phase to be optimized independently with dedicated instructions like gather, permute, and scatter operations.
Solution Approach 2:
A temporary register or buffer is introduced as an intermediary storage location between the scattered source data and the destination. This intermediary allows the processor to collect scattered elements, rearrange them in the intermediate storage, and then scatter them to the final destination, enabling complex rearrangements through composition of simpler operations.
2Productivity
If data rearrangement is implemented using multiple separate instructions, then the instruction set remains simple, but the number of instructions required increases and performance decreases
Solution Approach 1:
Multiple data rearrangement operations are merged into single composite instructions. For example, a gather-scatter operation that previously required separate gather, rearrangement, and scatter instructions is now performed by a single instruction that combines these functions, reducing instruction count and improving execution efficiency.
Solution Approach 2:
The processor implements universal data rearrangement instructions that can perform multiple types of rearrangements (gather, scatter, permute, shuffle) through a single instruction format with configurable parameters. This multi-functionality allows the same instruction to handle different rearrangement patterns without requiring separate specialized instructions for each case.
3Adaptability or versatility
If symmetric gather and scatter instructions are added to the processor, then algorithm versatility improves, but the device complexity increases
Solution Approach 1:
The processor implements asymmetric but complementary gather and scatter instructions that mirror each other in functionality but are optimized for their specific directions. The gather instruction is optimized for collecting scattered data into contiguous storage, while the scatter instruction is optimized for distributing contiguous data to scattered locations. This asymmetric design provides the needed symmetry for algorithms while maintaining instruction efficiency.
Data Source
AI summary
A processor includes a decode unit to decode an instruction indicating a source packed data operand having source data elements and indicating a destination storage location. Each of the source data elements has a source data element value and a source data element position. An execution unit, in response to the instruction, stores a result packed data operand having result data elements each having a result data element value and a result data element position. Each result data element value is one of: (1) equal to a source data element position of a source data element, closest to one end of the source operand, having a source data element value equal to the result data element position of the result data element; and (2) a replacement value, when no source data element has a source data element value equal to the result data element position of the result data element.