Processor Instruction Conversion Table for Dynamic Code Extension
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Solution Overview
Problem
Conventional processors face challenges in extending instruction sets due to increased code size and complexity when using escape codes, limiting the flexibility of bit field assignments and instruction lengths, which restricts the number of instruction types and operand lengths.
Innovation Solution
A processor with an instruction conversion table that associates bit patterns with extension fields, allowing for dynamic extension of instruction lengths by substituting extension fields for predetermined fields, enabling the decoding of new instructions with longer operation codes and operands, and including mode information for operand interpretation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If escape codes are used to extend the instruction set, then the number of instruction types is increased, but the code size becomes large and control complexity increases
Solution Approach 1:
The instruction format is segmented into multiple fields, with the operation code field being extendable through an extension field. This segmentation allows the instruction set to be extended without requiring escape codes, as the extension field is an integral part of the instruction structure. The instruction conversion table separates the base instruction fields from the extendable operation code portion, enabling systematic extension while maintaining structured control.
Solution Approach 2:
The patent extends the instruction set by adding another dimension to the operation code field through the extension field. Instead of using escape codes that add control complexity, the extension field provides an additional bit dimension that directly increases the number of available instruction types. The instruction conversion table maps base instructions to extended instructions by appending extension field bits, effectively adding a dimensional layer to the instruction space.
2Adaptability or versatility
If the instruction word length is increased to secure more instruction types and operand lengths, then the flexibility is improved, but the code size increases
Solution Approach 1:
The patent implements dynamic instruction encoding where the effective instruction word length varies based on the specific instruction type. The instruction conversion table allows certain instructions to access the extension field for longer operation codes and operands, while other instructions use the standard format. This dynamic approach ensures that code size increases only when extended instruction formats are actually used, rather than allocating fixed space for all possible extensions.
Solution Approach 2:
The patent changes the parameter of operation code length dynamically through the extension field. By using the instruction conversion table, the system can switch between standard and extended operation code lengths based on the instruction being executed. This parameter change allows the instruction set to accommodate longer operation codes and operands when needed, while maintaining compact encoding for instructions that don't require extension, thus optimizing code size.
3Device complexity
If bit field assignment is fixed at design time, then the decoder logic is simplified, but the adaptability to different applications is reduced
Solution Approach 1:
The instruction conversion table serves as an intermediary between the fixed decoder logic and the variable instruction requirements. The table stores pre-computed extension field values that correspond to base instructions, allowing the fixed decoder to generate variable-length operation codes by simply looking up and appending the appropriate extension field. This intermediary structure maintains simple decoder logic while providing application-specific adaptability through the configurable table contents.
Data Source
AI summary
A predetermined field of a fetched instruction is extended to secure an instruction type and an operand length. An instruction conversion table stores an extension field longer than the predetermined field in association with a bit pattern of the predetermined field of an instruction. An extension field acquisition unit acquires the extension field by referring to the instruction conversion table, with a bit pattern of the predetermined field of the fetched instruction. An instruction decoder performs a decoding process on a new instruction including the extension field in place of the predetermined field of the fetched instruction.