Inline Decode Micro-Operations for String Processing
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Solution Overview
Problem
Traditional string operations in computing environments, such as those using the z/Architecture, are inefficient due to their reliance on hardware or microcode implementations, which are not well-suited for variable length strings and result in suboptimal performance.
Innovation Solution
Implementing string operations, like Move String (MVST) and Compare Logical String (CLST), as inline straight-line code using instruction cracking, which expands the looping instructions into non-looping sequences of operations to process defined amounts of data concurrently, avoiding microcode entry and exit overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If string operations are implemented using hardware or microcode with looping instructions, then the operations can handle variable length strings, but the processing speed and efficiency deteriorate due to loop overhead and microcode entry/exit costs
Solution Approach 1:
The patent segments the string processing operation into fixed-size chunks (e.g., 16-byte blocks). Instead of processing the entire variable-length string in a single loop, the instruction divides the string into multiple fixed-size segments and processes them sequentially using straight-line code. This segmentation eliminates the need for looping control structures while still handling variable-length data by chaining multiple fixed-size operations together.
Solution Approach 2:
The patent dynamically adapts the number of straight-line operations based on the actual string length. The system calculates how many fixed-size chunks are needed to cover the variable-length string and generates the appropriate number of operation sequences. This dynamic adjustment allows the system to maintain high performance through unrolled loops while still accommodating variable input sizes.
2Device complexity
If looping instructions are used to process defined amounts of data, then the code is more compact and easier to implement, but the execution time increases due to loop overhead
Solution Approach 1:
The patent performs preliminary unrolling of the loop iterations into straight-line code sequences. Instead of executing a loop at runtime that iterates through the data, the system pre-expands the loop body into multiple sequential operations during instruction decoding or compilation. This preliminary action eliminates runtime loop overhead while maintaining the same functional behavior, directly addressing the time loss issue.
3Extent of automation
If microcode is used to implement string operations, then the operations can be performed in hardware, but the performance deteriorates due to microcode entry and exit overhead
Solution Approach 1:
The patent extracts the string processing logic from microcode and implements it directly in the main instruction execution path using straight-line code. By taking out the problematic microcode entry/exit overhead and replacing it with native processor instructions that execute in the main control flow, the system retains hardware-level performance while eliminating the performance penalty associated with microcode interpretation.
Data Source
AI summary
An instruction defined to be a looping instruction that repeats a plurality of times to perform an operation on a defined amount of data is obtained. The looping instruction is expanded into a sequence of operations. The sequence of operations is a non-looping sequence of operations to perform the operation on the defined amount of data.