Instruction Operand Prefixing for Extensible Decoding
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Solution Overview
Problem
Traditional computing systems face challenges in decoding instructions due to the limited length of instructions, which prevents the inclusion of all necessary fields, leading to a need for extending instruction sets while maintaining backward compatibility.
Innovation Solution
The implementation of instruction operand prefixing mechanisms that combine prefix instructions with existing instructions to create new, extended versions, allowing additional operands to be included, thereby enhancing instruction set extensibility and compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If instructions are kept short in length, then code size is reduced and processing efficiency is improved, but the ability to include all necessary fields for intended operations is limited
Solution Approach 1:
The instruction is divided into two parts: a short base instruction containing the operation code and essential fields, and a separate prefix operand containing additional operands. This segmentation allows the base instruction to remain short for efficient processing while the prefix operand provides additional fields when needed, resolving the contradiction between short length and field completeness.
Solution Approach 2:
A prefix operand acts as an intermediary between the short base instruction and the need for additional operands. The prefix operand is processed by a pre-decoder that identifies and combines it with the base instruction, mediating between the limited instruction length and the requirement for complete operational fields.
2Adaptability or versatility
If new instructions with additional operands are created, then instruction set versatility is improved, but backward compatibility with existing systems is compromised
Solution Approach 1:
The prefix operand mechanism provides a universal method for extending existing instructions. The same prefix operand structure can be applied to multiple different base instructions, allowing new functionality to be added across the instruction set without creating entirely new instruction formats, thus maintaining backward compatibility while achieving extensibility.
Solution Approach 2:
The prefix operand is processed in advance by a pre-decoder that identifies the prefix and combines it with the base instruction before execution. This preliminary action allows the extended instruction functionality to be prepared beforehand, ensuring that existing execution pipelines and decoding logic remain compatible with both original and extended instructions.
3Adaptability or versatility
If prefix operands are combined with base instructions to create extended instructions, then additional operands are included, but the complexity of the decoding mechanism increases
Solution Approach 1:
A pre-decoder stage is introduced that performs preliminary identification and combination of prefix operands with base instructions before the main decoder processes them. This preliminary action simplifies the main decoder's task by pre-processing the instruction format, reducing the overall decoding complexity despite the added functionality.
Solution Approach 2:
The pre-decoder acts as an intermediary between the instruction fetch stage and the main decoder. It handles the complex task of identifying prefix operands and combining them with base instructions, shielding the main decoder from the complexity while enabling enhanced operand inclusion capability.
Data Source
AI summary
A system comprising instruction operand prefixing combinators and decoders and various associated methods are provided for augmenting instruction operands using prefixing mechanisms to existing instructions to create new combined versions of the instructions that are executed. Hardware, computer program products and methods use the mechanisms and/or perform such combinations to include additional source or destination operands into instructions by way of combining them into the instructions. Variations in techniques allow augmenting existing instructions to execute with an added condition prefix to make them into conditional execution instructions. Furthermore, instructions can also be augmented with functions, and/or type operands and/or hints to modify instruction functionality to handle a wider class of operand types or classes of data, improve execution speeds, and instruction set extensibility while maintaining backward compatibility. Instruction extension capability facilitates rapid repurposing of highly used matrix and machine learning related instructions for rapidly changing deep learning models and algorithms.