Switch Statement Range Stride Check Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional encoding techniques are inefficient in recognizing stride values and performing range and stride checks in switch statements, leading to expensive branch table filling and potential branch misprediction, which affects processing performance.
Innovation Solution
A method and system that efficiently encode combined range and stride checks by analyzing case labels in switch statements, recognizing stride values, and generating code to perform range and stride checks without using branch instructions, thereby reducing the number of tests required and freeing up the branch target buffer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional encoding techniques are used for switch statements, then the code can be generated, but the branch table becomes large and inefficient due to filling gaps with default branches
Solution Approach 1:
The patent segments the branch table into multiple smaller tables, each handling a specific range of stride values. Instead of one large branch table filling all gaps with defaults, the code is divided into multiple lookup tables that each manage a portion of the stride space, reducing the size and complexity of each individual table while maintaining complete coverage of all possible stride values.
Solution Approach 2:
The patent introduces an additional dimension to the branch lookup process by using a two-level table structure. The first level determines which stride range is being accessed, and the second level provides the actual branch target within that range. This dimensional approach transforms a single large table problem into a hierarchy of smaller tables, improving efficiency without sacrificing completeness.
2Measurement precision
If three conditional branches are used to check range and stride, then the check is accurate, but the branch target buffer is consumed and misprediction risk increases
Solution Approach 1:
The patent replaces the mechanical branch instruction system with a computational lookup system. Instead of using three conditional branch instructions that require buffer entries and are subject to misprediction, the invention uses arithmetic operations to compute an index into a pre-computed branch table, substituting branching mechanics with direct memory access and arithmetic computation.
Solution Approach 2:
The patent performs preliminary action by pre-computing and storing branch targets in lookup tables during code generation. The complex logic of range and stride checking is resolved in advance and encoded into the table structure itself, so that runtime execution only requires simple index computation and table lookup, eliminating the need for runtime conditional branches.
3Adaptability or versatility
If default branches are used to fill gaps in the branch table, then all stride values can be handled, but the code becomes expensive and inefficient
Solution Approach 1:
The patent applies local quality by making different parts of the branch handling system specialized for different purposes. Each segment of the branch table is optimized for its specific stride range, and the table structure itself encodes the stride information locally. This eliminates the need for generic default branches that must handle all cases uniformly, allowing each local segment to be highly efficient for its specific purpose.
Data Source
AI summary
Embodiments of a method and system for compiling code, such as program-generated code, are disclosed herein. The method and system efficiently encode combined range and stride checks. For example, the method and system are operable to encode combined range and stride checks as they occur in a translation of switch statements. The method and system can generate code to perform the range and stride check, and to branch to the case body, if the range and stride checks are successful. The various embodiments may operate to provide an efficient code transformation, better code density, and processing performance. Other embodiments are described and claimed.