Compiler Structure Points for Cross-Lane Semantics
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Solution Overview
Problem
Compilers face challenges in preserving the intended semantics of cross-lane operations during the compilation process, leading to unpredictable and non-deterministic behavior due to optimizations and transformations in control flow graphs, especially in parallel execution models used in GPU and CPU programming.
Innovation Solution
The introduction of structure point intrinsic function calls and their conversion to post-dominating join (pjoin) representations, which are then transformed into reconverging control flow graphs to ensure predictable execution of cross-lane operations by inserting structure points and pjoin calls, constraining optimizations to maintain intended semantics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If compilers perform optimizations and transformations on control flow graphs, then productivity and execution efficiency are improved, but the semantics of cross-lane operations become unpredictable and non-deterministic
Solution Approach 1:
The patent introduces structure point intrinsic function calls as intermediary elements that mediate between the compiler's optimization processes and the cross-lane operations. These structure points act as markers that constrain how the control flow graph can be transformed, ensuring that optimizations do not violate the semantic requirements of cross-lane operations while still allowing efficiency improvements.
Solution Approach 2:
The patent applies preliminary actions by inserting structure point intrinsic function calls into the control flow graph before optimizations are performed. These structure points pre-establish constraints on valid transformations, guiding the compiler to perform optimizations that maintain semantic correctness. The conversion to post-dominating join representations further refines these constraints before the actual optimization process begins.
2Reliability
If structure point intrinsic function calls are inserted to preserve semantics, then reliability of cross-lane operations is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter representation of structure points from their initial form to post-dominating join representations. This parameter transformation simplifies the control flow graph by consolidating multiple structure points into fewer, more manageable join operations that are easier for the compiler to handle while maintaining the same semantic constraints.
Solution Approach 2:
The patent segments the control flow graph into regions bounded by structure points and post-dominating joins. This segmentation allows the compiler to independently optimize each segment while respecting the semantic constraints imposed by the structure points, reducing the overall complexity by breaking down the global optimization problem into smaller, more manageable local problems.
Data Source
AI summary
A computing system includes a processor and a memory storing instructions for a compiler that, when executed by the processor, cause the processor to generate a control flow graph of program source code by receiving the program source code in the compiler, in the compiler, generating a structure point representation based on the received program source code by inserting into the program source code a set of structure points including an anchor structure point and a join structure point associated with the anchor structure point, and based on the structure point representation, generating the control flow graph including a plurality of blocks each representing a portion of the program source code. In the control flow graph, a block A between the anchor structure point and the join structure point post-dominates each of the one or more divergent branches between the anchor structure point and the join structure point.