Speculative Register File Read Suppression Circuit
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Solution Overview
Problem
Data processing systems face inefficiencies in power consumption due to unnecessary read operations from speculative register files, as existing techniques fail to effectively determine when a read operation can be suppressed, leading to energy wastage.
Innovation Solution
Implementing read suppression circuitry that maintains a boundary pointer within an allocation sequence to identify a read-suppression region where no valid speculative register values exist, allowing for the suppression of unnecessary reads by comparing the position of the speculative register to be read with the boundary pointer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read operations are performed for all speculative register accesses, then source operand values can be obtained, but power consumption increases due to unnecessary reads
Solution Approach 1:
The patent performs preliminary determination of whether a speculative register contains a valid value before executing the read operation. By checking the validity status in advance, the system avoids performing unnecessary read operations on invalid registers, thereby reducing power consumption while ensuring that valid reads are not missed.
Solution Approach 2:
The patent introduces a validity parameter (valid/invalid status) for each speculative register that changes based on allocation and commit events. This parameter enables the system to dynamically adjust read operation execution, suppressing reads when invalid and performing them when valid, thus optimizing power consumption without compromising operand availability.
2Adaptability or versatility
If speculative registers are allocated frequently to support out-of-order execution, then instruction processing flexibility improves, but determining valid reads becomes more complex
Solution Approach 1:
The system performs preliminary tracking of speculative register allocation and commit events to pre-determine validity status before read operations are needed. This advance preparation simplifies the read determination process by having validity information ready, rather than performing complex analysis at the time of each read request.
Solution Approach 2:
Each speculative register maintains its own validity status indicator that is automatically updated by the allocation and commit mechanisms. This self-service approach allows the validity determination to be inherent in the register structure itself, reducing the complexity of external determination logic while supporting flexible out-of-order execution.
Data Source
AI summary
A single threaded out-of-order processor 2 includes an architected register file 22 and a speculative register file 20. Speculative register allocation circuitry 24 serves to allocate speculative registers for use in accordance with an allocation sequence and taken from a position determined by a tail point. Read suppression circuitry 30 serves to maintain a boundary pointer corresponding to a position within the allocation sequence such that no speculative register more recently allocated within the allocation sequence than that corresponding to the boundary pointer can have a valid register value. The read suppression circuitry 30 serves to suppress read operations for source operands lying within a read-suppression region delimited by the tail point and the boundary pointer. Separate boundary pointers may be maintained for different types of register values, such as integer register values and floating point register values.