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Constant-Loop Dominators for Single-Path Code Optimization

Authors Emad Jacob Maroun , Martin Schoeberl , Peter Puschner

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Author Details

Emad Jacob Maroun
  • Institute of Computer Engineering, TU Wien, Vienna, Austria
Martin Schoeberl
  • Department of Applied Mathematics and Computer Science, Technical University of Denmark, Lyngby, Denmark
Peter Puschner
  • Institute of Computer Engineering, TU Wien, Vienna, Austria

Acknowledgements

This work has been supported by the Doctoral College Resilient Embedded Systems, which is run jointly by the TU Wien’s Faculty of Informatics and the UAS Technikum Wien.

Cite AsGet BibTex

Emad Jacob Maroun, Martin Schoeberl, and Peter Puschner. Constant-Loop Dominators for Single-Path Code Optimization. In 21th International Workshop on Worst-Case Execution Time Analysis (WCET 2023). Open Access Series in Informatics (OASIcs), Volume 114, pp. 7:1-7:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)
https://doi.org/10.4230/OASIcs.WCET.2023.7

Abstract

Single-path code is a code generation technique specifically designed for real-time systems. It guarantees that programs execute the same instruction sequence regardless of runtime conditions. Single-path code uses loop bounds to ensure all loops iterate a fixed number of times equal to their upper loop bound. When the lower and upper bounds are equal, the loop must iterate the same number of times, which we call a constant loop. In this paper, we present the constant-loop dominance relation on control-flow graphs. It is a variation of the traditional dominance relation that considers constant loops to find basic blocks that are always executed the same number of times. Using this relation, we present an optimization that reduces the code needed to manage single-path code. Our evaluation shows significant performance improvements, with one example of up to 90%, with mostly minor effects on code size.

Subject Classification

ACM Subject Classification
  • Computer systems organization → Real-time systems
  • Theory of computation → Graph algorithms analysis
  • Theory of computation → Control primitives
  • General and reference → Performance
Keywords
  • single-path
  • dominators
  • algorithms
  • optimization
  • control-flow graph

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References

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