Microprocessor Shifting and Rounding Single Instruction
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Solution Overview
Problem
Existing digital signal processors (DSPs) face complexity in performing shifting and rounding operations, which can be improved for more efficient data manipulation.
Innovation Solution
A method and system within a DSP that performs shifting and rounding operations using a single instruction, where data is shifted right by an encoded bit value, a unitary integer is added, and further shifted to round the data to the next integer value, eliminating the need for a rounding module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional separate shifting and rounding modules are used in DSP, then rounding operations can be performed, but device complexity increases and cost increases
Solution Approach 1:
The patent merges the shifting operation and rounding operation into a single integrated instruction. The rounding function is achieved by combining a shift operation with an addition of 0.5 (implemented through bit manipulation), eliminating the need for a separate hardware rounding module. This is accomplished by executing a shift instruction that simultaneously performs the shift and adds the rounding offset in one operation.
Solution Approach 2:
The shift instruction is designed to perform multiple functions: it can perform both the data shifting operation and the rounding operation using the same instruction format and execution pathway. By making the shift instruction universal, the processor can handle both shifting and rounding without requiring dedicated hardware for each function, thereby reducing device complexity while maintaining full rounding capability.
2Productivity
If multiple instructions are used for shifting and rounding operations, then operations can be performed accurately, but productivity decreases
Solution Approach 1:
The patent combines multiple operations (shifting and rounding) into a single atomic instruction that executes in one cycle. The rounding accuracy is maintained by implementing the rounding offset addition (adding 0.5 before truncation) within the same instruction execution flow, ensuring numerical precision is not compromised while achieving single-instruction execution.
Solution Approach 2:
The rounding offset (0.5) is pre-calculated and embedded into the instruction execution pathway. Before the final truncation occurs, the rounding offset is automatically added to the shifted value, ensuring correct rounding behavior. This preliminary action of adding the offset is integrated into the single instruction execution, maintaining accuracy while improving productivity.
Data Source
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AI summary
A method and system to perform shifting and rounding operations within a microprocessor, such as, for example, a digital signal processor, during execution of a single instruction are described. An instruction to shift and round data within a source register unit of a register file structure is received within a processing unit. The instruction includes a shifting bit value indicating the bit amount for a right shift operation and is subsequently executed to shift data within the source register unit to the right by an encoded bit value, calculated by subtracting a single bit from the shifting bit value contained within the instruction. A predetermined bit extension is further inserted within the vacated bit positions adjacent to the shifted data. Subsequently, an addition operation is performed on the shifted data and a unitary integer value is added to the shifted data to obtain resulting data. Finally, the resulting data is further shifted to the right by a single bit value and a predetermined bit extension is inserted within the vacated bit position to obtain the final rounded data results to be stored within a destination register unit.