Move Elimination Circuitry for Processor Pipeline Optimization
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Solution Overview
Problem
The existing move elimination techniques in processor pipelines increase resource usage and complexity, particularly in the Rename Commit Queue (RCQ), leading to potential pipeline stalls due to increased logical register allocations, which can be limiting and affect throughput and power consumption.
Innovation Solution
Incorporating move elimination circuitry that adjusts register identities during the rename stage and demotion circuitry to reverse or inhibit these adjustments based on conditions such as RCQ capacity, Instructions Per Cycle, and latency flags to manage resource usage and prevent stalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If move elimination is performed to reduce power consumption and improve throughput, then resource usage in the Rename Commit Queue increases and pipeline stalls occur, but if move elimination is inhibited, then power consumption increases and throughput decreases
Solution Approach 1:
The system dynamically adjusts the application of move elimination based on real-time conditions. The demotion circuitry monitors RCQ capacity, IPC, and latency flags to determine when to apply or reverse move elimination adjustments, making the system adaptive to changing operational states rather than using a static approach
Solution Approach 2:
The system changes operational parameters (move elimination status) based on monitored conditions. When RCQ capacity is sufficient and performance thresholds are met, move elimination is applied; when conditions deteriorate, the demotion circuitry reverses the adjustment, effectively changing the system's operational mode to maintain optimal performance
2Loss of energy
If move elimination adjusts register identities to eliminate move operations, then power consumption decreases, but resource usage and complexity in the rename stage increase
Solution Approach 1:
The move elimination circuitry extracts and eliminates redundant move operations from the instruction stream by adjusting register identities in the rename stage. This removes unnecessary operations that would otherwise consume power, while the demotion circuitry provides a mechanism to extract or reverse adjustments when resource usage becomes excessive
Solution Approach 2:
The demotion circuitry implements feedback by monitoring conditions (RCQ capacity, IPC, latency flags) and reversing move elimination adjustments when thresholds are exceeded. This feedback mechanism prevents the system from entering a state where excessive resource usage would cause pipeline stalls, thereby managing the trade-off between power savings and system complexity
3Productivity
If move elimination is applied to eliminate redundant operations, then instructions per cycle increase, but pipeline stalls occur due to RCQ capacity constraints
Solution Approach 1:
The demotion circuitry performs preliminary checks of RCQ capacity, IPC, and latency flags before allowing move elimination adjustments to be applied. By evaluating conditions in advance, the system prevents situations where move elimination would exceed RCQ capacity and cause pipeline stalls, thereby maintaining continuous instruction flow
Data Source
AI summary
A data processing apparatus is provided that comprises rename circuitry for performing a register rename stage of a pipeline in respect of a stream of operations. Move elimination circuitry performs a move elimination operation on the stream of operations in which a move operation is eliminated and the register rename stage performs an adjustment of an identity of registers in the stream of operations to compensate for the move operation being eliminated and demotion circuitry reverses or inhibits the adjustment in response to one or more conditions being met.