Processor Exception Handling via Instruction Age Tracking
Solution Overview
Problem
Processors face challenges in handling exceptions during instruction execution, such as data access timeouts, arithmetic overflows, and invalid instructions, which can lead to errors and require efficient exception handling mechanisms to maintain data integrity and processing continuity.
Innovation Solution
A processor-implemented method for exception handling involves maintaining an ordered list of instructions using pointers, detecting execution exceptions, determining the effective age of instructions, and initiating an exception handling routine based on matching the age with pointers, allowing for out-of-order execution and delayed handling to prevent data damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an exception handling routine is initiated immediately upon detecting an execution exception, then the exception is addressed promptly, but valid data may be overwritten or lost and instructions not causing exceptions cannot complete
Solution Approach 1:
The system performs preliminary actions by saving the state of the instruction buffer and identifying the specific instruction causing the exception before initiating the exception handling routine. This allows the system to restore only the necessary state later, rather than conservatively blocking all instructions or overwriting data immediately.
Solution Approach 2:
The system discards the erroneous instruction that caused the exception while recovering and continuing execution of subsequent valid instructions. The exception handling routine identifies and removes only the problematic instruction from the buffer, allowing other instructions to complete successfully.
2Device complexity
If instructions are executed strictly in order, then exception handling is simplified, but processor performance and throughput are reduced
Solution Approach 1:
The instruction buffer is segmented into individual instruction entries, each with metadata including age information. This segmentation allows the system to identify and handle exceptions at the individual instruction level rather than requiring complete buffer rollback, enabling out-of-order execution while maintaining exception handling capability.
Solution Approach 2:
An intermediary mechanism (the age tracking system) is introduced between the out-of-order execution unit and the exception handling routine. This intermediary tracks the temporal order of instructions independently from their execution order, allowing the exception handler to identify the first erroneous instruction even when instructions execute out of order.
3Productivity
If a reorder buffer is used to manage out-of-order execution and exception handling, then instruction completion is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential functionality needed for exception handling from a full reorder buffer implementation. Instead of implementing complete reordering capability, the system maintains an ordered list with age tracking information, taking out only the minimum necessary structure to identify the first erroneous instruction while supporting out-of-order execution.
Solution Approach 2:
The system uses simple, lightweight data structures (ordered list with pointer and age field) rather than complex reorder buffer structures. These simple structures are easily created and discarded, providing the necessary exception handling capability without the overhead of sophisticated buffer management.
Data Source
AI summary
Techniques for instruction execution based on processor instruction exception handling are disclosed. A processor core is accessed. The processor core executes at least one instruction thread. The processor core executes one or more instructions out of order. An ordered list of instructions is maintained. The ordered list is based on instructions that are presented to the processor core for execution. The ordered list is organized using one or more pointers. An execution exception is detected in the processor core. The execution exception corresponds to one of the instructions in the ordered list. The execution exception requires initiating an exception handling routine. An effective age of an instruction in the ordered list is determined. The effective age corresponds to the execution exception. The exception handling routine is initiated, based on matching the effective age of an instruction in the ordered list with one of the one or more pointers.