Processor Register Reclamation via Active Status Indicators
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Solution Overview
Problem
Out-of-order execution processors face limitations due to a limited number of architectural registers, which restrict the number of instructions that can be in flight, as multiple uses of a particular architectural register may represent independent variables, leading to reduced instruction throughput and increased latencies.
Innovation Solution
Implementing a method to reclaim physical registers renamed as microcode architectural registers, using indicators to determine active pointers and store information in a committed rename alias data structure, allowing for concurrent reclamation upon exiting a microcode routine, thereby increasing the availability of physical registers for instruction set architectural registers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If physical registers are permanently assigned to architectural registers including microcode architectural registers, then register mapping is simplified, but the number of available physical registers for instruction set architectural registers is reduced
Solution Approach 1:
The patent implements dynamic register mapping by introducing an active status indicator that allows the processor to dynamically determine which physical registers are available for instruction set architectural registers. The system transitions from static permanent assignments to dynamic conditional assignments based on whether microcode architectural registers are currently active, enabling flexible resource allocation that resolves the contradiction between mapping simplicity and register availability.
Solution Approach 2:
The patent changes the parameter of register availability by introducing an active status indicator that modifies the effective number of available physical registers. When microcode architectural registers are inactive, their associated physical registers become available for instruction set architectural registers, effectively changing the quantity of available registers without requiring permanent reassignment or complex dynamic renaming mechanisms.
2Productivity
If multiple uses of architectural registers are treated as independent variables, then more instructions can be in flight, but register dependencies increase latency
Solution Approach 1:
The patent segments the register file into two distinct sets: physical registers assigned to instruction set architectural registers and physical registers assigned to microcode architectural registers. This segmentation allows independent management of register dependencies for different instruction types, enabling more instructions to be in flight simultaneously while reducing latency by preventing false dependencies between independent register uses through separate physical register allocation.
3Productivity
If physical registers are reclaimed when no longer needed, then register utilization improves, but concurrent reclamation of microcode architectural registers is not supported
Solution Approach 1:
The patent merges the reclamation mechanisms for instruction set architectural registers and microcode architectural registers into a unified concurrent reclamation system. Both register types are managed through the same active status indicator and reclamation logic, allowing physical registers to be reclaimed concurrently from either source without requiring separate complex reclamation mechanisms, thus improving register utilization while maintaining manageable system complexity.
Data Source
AI summary
A method of operating a processor includes reclaiming a physical register renamed as a microcode architectural register used by a microcode routine. The physical register is reclaimed according to an indicator corresponding to the microcode architectural register and indicating that a pointer to the physical register and corresponding to the microcode architectural register is an active pointer.