Recirculation Queue for Load-Store Issue Queue Deallocation

Solution Overview

Problem

Existing processor cores have resource-intensive issue queues that require significant power and die area due to the need to store operands, relative addresses, and other fields for load-store operations, limiting their efficiency.

Innovation Solution

Implementing a recirculation queue that stores only the effective address for load operations and the store value for store operations, allowing rejected load-store operations to be reissued from the recirculation queue rather than the original issue queue, thereby reducing power and area requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If issue queues store complete operation information including operands and control fields, then operations can be properly executed and tracked, but power consumption and die area increase significantly

Engineering Contradiction:

Improveoperation execution correctnessVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The patent segments the issue queue into two distinct structures: a traditional issue queue that stores complete operation information (operands, control fields) for a limited number of entries, and a recirculation queue that stores only effective addresses for load-store operations. This segmentation allows the system to maintain execution correctness while reducing the storage requirements and power consumption for load-store operation tracking.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts the effective address information from the complete issue queue entries and places it in a separate recirculation queue. By taking out only the essential address information needed for load-store operations while leaving the full operation details in the original issue queue, the system reduces the power and area requirements for tracking load-store operations without compromising execution correctness.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If issue queues store complete operation information including operands and control fields, then operations can be properly executed and tracked, but die area increases significantly

Engineering Contradiction:

Improveoperation execution correctnessVSAvoiddie area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent segments the issue queue into two distinct structures: a traditional issue queue that stores complete operation information (operands, control fields) for a limited number of entries, and a recirculation queue that stores only effective addresses for load-store operations. This segmentation allows the system to maintain execution correctness while reducing the storage requirements and power consumption for load-store operation tracking.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts the effective address information from the complete issue queue entries and places it in a separate recirculation queue. By taking out only the essential address information needed for load-store operations while leaving the full operation details in the original issue queue, the system reduces the power and area requirements for tracking load-store operations without compromising execution correctness.

Inventive Principle:

Principle #2Taking out (Extraction)

3Use of energy by stationary object

If the issue queue is made smaller to reduce power and area, then resource efficiency improves, but the ability to handle rejected load-store operations decreases

Engineering Contradiction:

Improvepower consumptionVSAvoidhandling rejected operations

Core Design Contradiction:

Use of energy by stationary objectVSAdaptability or versatility

Solution Approach 1:

The patent introduces a recirculation queue as an intermediary structure between the issue queue and the load-store pipeline. This intermediary holds effective addresses of load-store operations after they leave the issue queue, enabling the system to handle rejected operations by reissuing them from the recirculation queue rather than requiring the original issue queue entries to persist.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12061909B2Parallel slice processor having a recirculating load-store queue for fast deallocation of issue queue entries

Publication Date: 2024.08.13 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An execution unit circuit for use in a processor core provides efficient use of area and energy by reducing the per-entry storage requirement of a load-store unit issue queue. The execution unit circuit includes a recirculation queue that stores the effective address of the load and store operations and the values to be stored by the store operations. A queue control logic controls the recirculation queue and issue queue so that that after the effective address of a load or store operation has been computed, the effective address of the load operation or the store operation is written to the recirculation queue and the operation is removed from the issue queue, so that address operands and other values that were in the issue queue entry no longer require storage. When a load or store operation is rejected by the cache unit, it is subsequently reissued from the recirculation queue.