Debug Instruction Execution Control via Dynamic Register
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Solution Overview
Problem
Debug instructions in software development can cause undesired exceptions when left in finalized code, altering execution characteristics and making systems less predictable, especially in real-time applications.
Innovation Solution
Implementing debug instructions that can operate as 'no-op' instructions or be suppressed, allowing them to remain in the code without executing, and grouping debug instructions for independent control, enabling dynamic modification by hardware or software debuggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If debug instructions are removed from finalized code, then execution predictability is improved, but code integrity and development efficiency deteriorate
Solution Approach 1:
The debug instruction execution mode is made dynamic through a control register that can be modified by hardware or software debuggers. The control register contains an execution enable bit that dynamically switches between executing debug instructions and treating them as no-ops, allowing the system to adapt execution behavior based on debugging needs without changing the code image.
Solution Approach 2:
The execution behavior of debug instructions is controlled by changing a parameter in the control register (the execution enable bit). When this bit is set, debug instructions execute normally; when cleared, they are treated as no-ops. This parameter change allows the same code image to exhibit different execution characteristics without modification.
2Ease of manufacture
If debug instructions are left in finalized code, then code integrity is maintained, but execution predictability deteriorates due to undesired exceptions
Solution Approach 1:
The system dynamically controls whether debug instructions generate exceptions or are treated as no-ops through the execution enable bit in the control register. During normal execution, the bit is cleared to prevent exceptions; during debugging, it is set to enable debug operations, thus maintaining code integrity while ensuring execution predictability.
Solution Approach 2:
The control register acts as an intermediary between the debug instructions and the execution engine. It mediates the execution behavior by providing a control mechanism that can suppress or enable debug instruction effects without removing the instructions from the code, thus preventing undesired exceptions while maintaining code integrity.
3Reliability
If debug instructions are suppressed from execution, then execution predictability is improved, but debugging flexibility deteriorates
Solution Approach 1:
The execution control is made dynamic through the control register that can be modified by hardware or software debuggers. This allows the system to switch between suppression mode (for predictability) and execution mode (for debugging flexibility) as needed, with the ability to independently control multiple debug instruction groups.
Solution Approach 2:
Debug instructions are divided into independent groups, each with its own control in the control register. This segmentation allows selective suppression or execution of specific debug instruction groups while maintaining others, providing both execution predictability for non-debug groups and debugging flexibility for active groups.
Data Source
AI summary
A method includes providing a debug instruction and providing a debug control register field, where if the debug control register field has a first value, the debug instruction executes a debug operation and where if the debug control register field has a second value, the debug instruction is to be executed as a no-operation (NOP) instruction. A data processing system includes instruction fetch circuitry for receiving a debug instruction, a debug control register field, and debug execution control circuitry for controlling execution of the debug instruction in a first manner if the debug control register field has a first value and in a second manner if the debug control register field has a second value, where in the first manner a debug operation is performed and in the second manner no debug operation is performed.