Processor Partial Register Write Logic
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Solution Overview
Problem
Modern processors face inefficiencies in executing instructions due to the need for additional instructions to handle partial register writes, which constrain instruction scheduling and increase data copy operations, especially when dealing with instructions of differing operand widths.
Innovation Solution
A processor is adapted to perform partial write operations that preserve at least a portion of the destination location, allowing it to act as a source location, using a three-operand instruction format with a partial write indicator to efficiently handle partial register writes without additional merge instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional instructions are used to handle partial register writes, then register data consistency is ensured, but instruction scheduling flexibility is reduced and data copy operations increase
Solution Approach 1:
The patent merges the partial write operation with a read operation into a single atomic instruction. The execution unit reads the destination register, performs the write operation on the specified portion, and writes back the result in one unified operation, eliminating the need for separate read-modify-write sequences and maintaining data consistency without reducing scheduling flexibility.
Solution Approach 2:
The execution unit is designed to handle both full-width and partial-width write operations using the same architectural framework. The partial write indicator bit enables the unit to perform selective writes without requiring different instruction formats or additional specialized instructions, thereby maintaining scheduling flexibility while ensuring data consistency.
2Reliability
If additional instructions are used to handle partial register writes, then register data consistency is ensured, but the number of instructions and data copy operations increases
Solution Approach 1:
The patent combines multiple operations (read, write, and data copy) into a single atomic partial write instruction. This eliminates the need for separate instructions to read the destination register, perform the write, and potentially copy data, thereby reducing the total instruction count while maintaining register data consistency through the atomic nature of the operation.
Solution Approach 2:
The execution unit automatically handles the complexity of partial writes by using the partial write indicator bit to direct the write operation to the correct portion of the destination register. The system serves itself by automatically determining where to write without requiring additional instructions to calculate addresses or manage data copying, thus reducing overall device complexity.
3Productivity
If full width registers are used for all operations, then processing width is maximized, but instructions taking advantage of full processing width are constrained
Solution Approach 1:
The patent enables partial register writes by allowing instructions to write to only the necessary portion of a full-width register rather than requiring full-width writes. The partial write indicator bit specifies the exact width and location of the write operation, allowing instructions to be as flexible as needed while still utilizing the full processing width when beneficial, thus resolving the constraint on instruction operand width flexibility.
Data Source
AI summary
In one embodiment, a processor includes logic, responsive to a first instruction, to perform an operation on a first source operand and a second source operand associated with the first instruction and write a result of the operation to a destination location comprising a third source operand. The write may be a partial write of the destination location to maintain an unmodified portion of the third source operand. Other embodiments are described and claimed.