Debugging Prefixed Code Using Trap Instructions
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Solution Overview
Problem
The debugging of code containing prefix instructions is challenging due to the limitations imposed by the size of directly addressable data ranges, which restricts the size of global data areas and complicates debugging processes.
Innovation Solution
A computer program product that uses traps to debug application code with prefix instructions, where a trap replaces the prefixed instruction, reports the presence of the prefix, and ignores it during execution, allowing for efficient debugging and code modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If prefix instructions are used to extend addressability, then the directly addressable data range is increased, but the debugging complexity increases due to prefix handling requirements
Solution Approach 1:
The patent extracts the prefix handling logic from the normal instruction execution path by introducing a separate prefix storage facility and prefix detection mechanism. The trap instruction isolates prefix information in a dedicated register, separating it from the main execution flow and allowing independent handling of prefix and instruction debugging.
Solution Approach 2:
The prefix storage facility acts as an intermediary between the prefix instruction and the prefixed instruction. It stores prefix information (such as address extensions) and makes it available to the execution unit without requiring the debugging mechanism to directly interpret or handle the prefix-modified instruction semantics.
2Reliability
If traps are inserted to debug prefixed instructions, then debugging capability is improved, but the trap execution may be incorrectly modified by the prefix
Solution Approach 1:
The patent performs preliminary detection of prefix instructions before executing the trap. The system checks whether a prefix is present and, if so, prevents the prefix from modifying the trap instruction. This preliminary action ensures that the trap executes with its original semantics unchanged by any prefix.
Solution Approach 2:
The patent applies a counter-action to nullify the prefix effect on trap instructions. When a prefix is detected before a trap, the system actively prevents the prefix from taking effect on the trap instruction, thereby counteracting what would otherwise be a harmful modification to the trap's execution behavior.
3Quantity of substance
If breakpoints are set over prefix or prefixed instructions, then code coverage is improved, but the execution flow management becomes more complex
Solution Approach 1:
The patent segments the instruction stream into distinct prefix instructions and prefixed instructions. This segmentation allows the debugging system to independently track and manage breakpoints for each segment, simplifying execution flow management while maintaining comprehensive code coverage through separate handling of prefix and instruction portions.
Data Source
AI summary
A debugging capability that enables the efficient debugging of code that has prefixes, referred to herein as prefixed code. To debug application code, in which the application code includes a prefixed instruction to be modified by a prefix, a trap is provided. The trap is configured to report a presence of the prefix, but to otherwise perform the trap functions absent the prefix; i.e., the prefix is otherwise ignored in the processing of the trap.