Move Prefix Instruction for Reduced Circuit Area
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Solution Overview
Problem
Instruction fusion is costly in terms of circuit area and power consumption, making it unfeasible for low-end systems where energy efficiency is prioritized over performance, due to the need for complex hardware and additional state maintenance to identify and check compatibility between move and data processing instructions across page or cache-line boundaries.
Innovation Solution
A dedicated move prefix instruction is introduced that allows the programmer or compiler to signal the instruction fusing circuitry to fuse a move prefix instruction with an immediately following instruction without needing to compare registers, reducing hardware overhead and enabling fusion in lower-end systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If instruction fusing circuitry is implemented to detect and fuse move instructions with data processing instructions, then processing performance is improved, but circuit area and power consumption increase significantly
Solution Approach 1:
The patent extracts the register comparison function from the instruction fusing circuitry by introducing a separate move prefix instruction that explicitly signals fusion eligibility. This removes the need for complex comparator circuits that would otherwise be required to check register compatibility between move and data processing instructions.
Solution Approach 2:
The move prefix instruction acts as an intermediary signal between the move instruction and the data processing instruction. Instead of directly comparing registers, the prefix instruction mediates the fusion process by providing explicit fusion eligibility information to the instruction fusing circuitry, simplifying the detection mechanism.
2Productivity
If instruction fusing circuitry is implemented to detect and fuse move instructions with data processing instructions, then processing performance is improved, but power consumption increases significantly
Solution Approach 1:
The patent extracts the register comparison function from the instruction fusing circuitry by introducing a separate move prefix instruction that explicitly signals fusion eligibility. This removes the need for complex comparator circuits that would otherwise be required to check register compatibility between move and data processing instructions.
Solution Approach 2:
The move prefix instruction acts as an intermediary signal between the move instruction and the data processing instruction. Instead of directly comparing registers, the prefix instruction mediates the fusion process by providing explicit fusion eligibility information to the instruction fusing circuitry, simplifying the detection mechanism.
3Measurement precision
If register comparison circuits are added to verify compatibility between move and data processing instructions, then fusion accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts the register comparison function from the instruction fusing circuitry by introducing a separate move prefix instruction that explicitly signals fusion eligibility. This removes the need for complex comparator circuits that would otherwise be required to check register compatibility between move and data processing instructions.
Data Source
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AI summary
An apparatus 2 has instruction fusing circuitry 50 for fusing two or more instructions fetched from a data store to generate a fused instruction to be processed by processing circuitry 14. A move prefix instruction is provided which indicates to the instruction fusing circuitry 50 that the move prefix instruction can be fused with an immediately following data processing instruction without needing to compare registers specified by the move prefix instruction and the immediately following instruction. This enables the instruction fusing circuitry 50 to be implemented with reduced hardware and energy cost.