Instruction Trace Registers for Debugging
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Solution Overview
Problem
Current solutions fail to accurately determine which instruction in a program code is responsible for updating values in processor registers, making it difficult to identify the source of register value changes during program execution.
Innovation Solution
The implementation of instruction trace registers, where the address of the last instruction updating a value in a processor register is stored, allowing for the identification of responsible instructions and enabling the generation of an execution path through the program code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional register storage is used, then the processor structure remains simple, but the ability to identify which instruction updated register values is lost
Solution Approach 1:
The patent embeds instruction trace registers within the existing processor register structure. Each instruction trace register is nested alongside its corresponding processor register, creating a hierarchical organization where the trace register contains the address information of the instruction that last updated the associated processor register value. This nesting approach adds the identification capability without requiring a completely separate tracking system.
Solution Approach 2:
The instruction trace register acts as an intermediary between the processor registers and the debugging/maintenance tools. Instead of directly tracking instruction updates through complex hardware logic, the trace register serves as a mediator that stores the address information, allowing external tools to query and analyze register update history without interfering with the core processor operations.
2Reliability
If instruction trace registers are added to track each processor register, then debugging capability is improved, but the device complexity increases
Solution Approach 1:
The instruction trace registers are designed to serve multiple purposes: they support debugging operations, enable crash analysis by preserving the state of the last instructions that modified register values, and provide information for performance analysis. This multi-functionality justifies the added hardware complexity by delivering multiple benefits from a single structural addition.
Solution Approach 2:
Rather than implementing a single complex tracking mechanism for all registers, the patent segments the tracking function into individual instruction trace registers, each associated with specific processor registers. This segmentation allows for granular control and enables the system to track only the necessary register updates, reducing the overall complexity compared to a universal tracking approach.
3Measurement precision
If addresses are copied to instruction trace registers on every register update, then accurate tracking is achieved, but the processing overhead increases
Solution Approach 1:
The instruction trace register updates are performed as part of the normal instruction execution pipeline, specifically during the commit stage when register updates are finalized. By integrating the trace register update into the existing execution flow rather than adding a separate tracking step, the system achieves accurate tracking without significant overhead, as the address copying occurs naturally during the instruction commit process.
Data Source
AI summary
A computer implemented method, apparatus, and computer usable program product for utilizing instruction trace registers. In one embodiment, a value in a target processor register in a plurality of processor registers is updated in response to executing an instruction associated with program code. In response to updating the value in the target processor register, an address for the instruction is copied from an instruction address register into an instruction trace register associated with the target processor register. The instruction trace register holds the address of the instruction that updated the value stored in the target processor register.