Temporary Register Reuse in Processing Pipelines
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Solution Overview
Problem
In data processing systems with multiple register files, the frequent allocation of new temporary registers for temporary-register-using instructions leads to unnecessary register move operations, occupying pipeline slots and bandwidth, and increasing power consumption, especially when multiple instructions reuse the same source register.
Innovation Solution
The processing pipeline detects whether a temporary-register-using instruction follows an earlier instruction that specified the same source register, and if so, reuses the temporary variable stored in the second register file, suppressing the need for additional register move micro-operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a new temporary register is allocated for each temporary-register-using instruction, then the instruction can be executed correctly, but unnecessary register move operations are generated consuming pipeline slots and bandwidth
Solution Approach 1:
The patent recovers and reuses temporary registers that are no longer needed by earlier instructions. When a later temporary-register-using instruction requests a temporary register, the system checks if an earlier instruction's temporary register is still valid (not overwritten by intervening instructions). If valid, the later instruction reuses that register instead of allocating a new one, thereby discarding the notion that each instruction needs a dedicated temporary register and recovering the register resource for reuse.
Solution Approach 2:
The patent makes temporary registers universal by allowing them to serve multiple temporary-register-using instructions rather than being dedicated to a single instruction. A temporary register allocated for an earlier instruction can be reused by later instructions that need temporary storage, making the register serve multiple functions and multiple instructions, thereby reducing the total number of temporary registers needed and eliminating redundant register move operations.
2Reliability
If new temporary registers are allocated for each instruction, then register availability is maintained, but register pressure increases causing potential stalls
Solution Approach 1:
The system discards the conservative approach of maintaining dedicated temporary registers for each instruction and instead recovers temporary registers for reuse. By tracking which temporary registers are still valid (not overwritten), the system can safely reuse them, thereby reducing register pressure while maintaining reliability through validation checks.
Solution Approach 2:
The patent changes the parameter of register allocation from static (one register per instruction) to dynamic (registers allocated and reused based on actual needs). The system monitors the validity state of temporary registers and allocates them dynamically, changing the register availability parameter from a fixed guarantee to a validated flexible state, thereby reducing register pressure while maintaining reliability.
3Reliability
If register move micro-operations are processed for each temporary-register-using instruction, then data is transferred correctly, but pipeline slots are occupied reducing overall throughput
Solution Approach 1:
The patent discards redundant register move micro-operations by recovering and reusing temporary registers. When a later instruction can reuse a temporary register from an earlier instruction, the system discards the unnecessary register move operation that would have transferred data again, thereby maintaining data transfer accuracy (the data is already in the correct register) while improving pipeline throughput by eliminating wasted operations.
Solution Approach 2:
The patent extracts and removes redundant register move micro-operations from the instruction execution flow. By detecting when a temporary register can be reused, the system extracts the unnecessary data transfer step and removes it from the pipeline, thereby maintaining correctness (the data is already where it needs to be) while improving throughput by reducing the number of micro-operations that must be processed.
Data Source
AI summary
An apparatus has a processing pipeline, and first and second register files. A temporary-register-using instruction is supported which controls the pipeline to perform an operation using a temporary variable derived from an operand stored in the first register file. In response to the instruction, when a predetermined condition is not satisfied, the pipeline processes at least one register move micro-operation to transfer data from the at least one source register of the first register file to at least one newly allocated temporary register of the second register file. When the condition is satisfied, the operation can be performed using a temporary variable already stored in the temporary register of the second register file used by an earlier temporary-register-using instruction specifying the same source register for determining the temporary variable, in the absence of an intervening instruction for rewriting the source register.