Execution Pipeline Bypass Network for Data Forwarding
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Solution Overview
Problem
In micro-processing systems, data dependencies between instructions in the execution pipeline lead to delays as data must pass through a load/store portion, causing stalls and inefficiencies due to the need for data to be available before it can be consumed.
Innovation Solution
A method is introduced to detect and exploit data forwarding opportunities by identifying intervening operations that form an identity function, allowing direct data forwarding from a producer to a consumer within the execution pipeline, bypassing the load/store portion, thereby reducing the time data is available for consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If data is forwarded through the load/store portion to the execution subunit, then data can be made available to the consumer, but pipeline stalls occur and time is lost while waiting for data
Solution Approach 1:
The patent extracts the data forwarding path from the load/store portion by introducing a dedicated bypass network that directly connects the producing execution subunit to the consuming execution subunit. This separates the data forwarding function from the traditional load/store portion, allowing data to be forwarded without passing through memory operations, thereby eliminating pipeline stalls and reducing time loss.
Solution Approach 2:
The bypass network acts as an intermediary mechanism that enables direct data transfer between execution subunits. Instead of data traveling through the load/store portion as an intermediate step, the bypass network provides a direct conduit, eliminating the need for memory reads and writes in the process, thus resolving the time loss and productivity issues.
2Reliability
If the scheduler stalls execution until data is available in the load/store portion, then data can be consumed, but execution time increases
Solution Approach 1:
The patent implements preliminary action by detecting data forwarding opportunities early in the pipeline (e.g., at the decode stage) and proactively establishing bypass paths before the data is actually needed. The scheduler identifies when a producing subunit will make data available and pre-configures the bypass network, allowing the consuming subunit to receive data as soon as it is produced, without waiting for the load/store portion or experiencing execution stalls.
3Adaptability or versatility
If data must pass through the load/store portion, then data can be loaded into memory, but the pipeline cannot proceed simultaneously
Solution Approach 1:
The patent segments the data forwarding path into two independent routes: the traditional load/store portion for memory operations and the new bypass network for internal data transfer. This segmentation allows the bypass network to handle data forwarding between execution subunits without interfering with memory operations, enabling simultaneous instruction execution and maintaining productivity while preserving data loading capability through the load/store portion when needed.
Data Source
AI summary
In one embodiment, in an execution pipeline having a plurality of execution subunits, a method of using a bypass network to directly forward data from a producing execution subunit to a consuming execution subunit is provided. The method includes producing output data with the producing execution subunit, consuming input data with the consuming execution subunit, for one or more intervening operations whose input is the output data from the producing execution subunit and whose output is the input data to the consuming execution subunit, evaluating those one or more intervening operations to determine whether their execution would compose an identify function, and if the one or more intervening operations would compose such an identity function, controlling the bypass network to forward the producing execution subunit's output data directly to the consuming execution subunit.