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Documents authored by Gebhard, Gernot


Document
Embedded Program Annotations for WCET Analysis

Authors: Bernhard Schommer, Christoph Cullmann, Gernot Gebhard, Xavier Leroy, Michael Schmidt, and Simon Wegener

Published in: OASIcs, Volume 63, 18th International Workshop on Worst-Case Execution Time Analysis (WCET 2018)


Abstract
We present __builtin_ais_annot(), a user-friendly, versatile way to transfer annotations (also known as flow facts) written on the source code level to the machine code level. To do so, we couple two tools often used during the development of safety-critical hard real-time systems, the formally verified C compiler CompCert and the static WCET analyzer aiT. CompCert stores the AIS annotations given via __builtin_ais_annot() in a special section of the ELF binary, which can later be extracted automatically by aiT.

Cite as

Bernhard Schommer, Christoph Cullmann, Gernot Gebhard, Xavier Leroy, Michael Schmidt, and Simon Wegener. Embedded Program Annotations for WCET Analysis. In 18th International Workshop on Worst-Case Execution Time Analysis (WCET 2018). Open Access Series in Informatics (OASIcs), Volume 63, pp. 8:1-8:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)


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@InProceedings{schommer_et_al:OASIcs.WCET.2018.8,
  author =	{Schommer, Bernhard and Cullmann, Christoph and Gebhard, Gernot and Leroy, Xavier and Schmidt, Michael and Wegener, Simon},
  title =	{{Embedded Program Annotations for WCET Analysis}},
  booktitle =	{18th International Workshop on Worst-Case Execution Time Analysis (WCET 2018)},
  pages =	{8:1--8:13},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-073-6},
  ISSN =	{2190-6807},
  year =	{2018},
  volume =	{63},
  editor =	{Brandner, Florian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2018.8},
  URN =		{urn:nbn:de:0030-drops-97543},
  doi =		{10.4230/OASIcs.WCET.2018.8},
  annote =	{Keywords: Worst-Case Execution Time (WCET) Analysis, Annotation Support, CompCert, Tool Coupling, aiT}
}
Document
Fine-Grain Iterative Compilation for WCET Estimation

Authors: Isabelle Puaut, Mickaël Dardaillon, Christoph Cullmann, Gernot Gebhard, and Steven Derrien

Published in: OASIcs, Volume 63, 18th International Workshop on Worst-Case Execution Time Analysis (WCET 2018)


Abstract
Compiler optimizations, although reducing the execution times of programs, raise issues in static WCET estimation techniques and tools. Flow facts, such as loop bounds, may not be automatically found by static WCET analysis tools after aggressive code optimizations. In this paper, we explore the use of iterative compilation (WCET-directed program optimization to explore the optimization space), with the objective to (i) allow flow facts to be automatically found and (ii) select optimizations that result in the lowest WCET estimates. We also explore to which extent code outlining helps, by allowing the selection of different optimization options for different code snippets of the application.

Cite as

Isabelle Puaut, Mickaël Dardaillon, Christoph Cullmann, Gernot Gebhard, and Steven Derrien. Fine-Grain Iterative Compilation for WCET Estimation. In 18th International Workshop on Worst-Case Execution Time Analysis (WCET 2018). Open Access Series in Informatics (OASIcs), Volume 63, pp. 9:1-9:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)


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@InProceedings{puaut_et_al:OASIcs.WCET.2018.9,
  author =	{Puaut, Isabelle and Dardaillon, Micka\"{e}l and Cullmann, Christoph and Gebhard, Gernot and Derrien, Steven},
  title =	{{Fine-Grain Iterative Compilation for WCET Estimation}},
  booktitle =	{18th International Workshop on Worst-Case Execution Time Analysis (WCET 2018)},
  pages =	{9:1--9:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-073-6},
  ISSN =	{2190-6807},
  year =	{2018},
  volume =	{63},
  editor =	{Brandner, Florian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2018.9},
  URN =		{urn:nbn:de:0030-drops-97556},
  doi =		{10.4230/OASIcs.WCET.2018.9},
  annote =	{Keywords: Worst-Case Execution Time Estimation, Compiler optimizations, Iterative Compilation, Flow fact extraction, Outlining}
}
Document
Software Structure and WCET Predictability

Authors: Gernot Gebhard, Christoph Cullmann, and Reinhold Heckmann

Published in: OASIcs, Volume 18, Bringing Theory to Practice: Predictability and Performance in Embedded Systems (2011)


Abstract
Being able to compute worst-case execution time bounds for tasks of an embedded software system with hard real-time constraints is crucial to ensure the correct (timing) behavior of the overall system. Any means to increase the (static) time predictability of the embedded software are of high interest -- especially due to the ever-growing complexity of such software systems. In this paper we study existing coding proposals and guidelines, such as MISRA-C, and investigate whether they simplify static timing analysis. Furthermore, we investigate how additional knowledge, such as design-level information, can further aid in this process.

Cite as

Gernot Gebhard, Christoph Cullmann, and Reinhold Heckmann. Software Structure and WCET Predictability. In Bringing Theory to Practice: Predictability and Performance in Embedded Systems. Open Access Series in Informatics (OASIcs), Volume 18, pp. 1-10, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2011)


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@InProceedings{gebhard_et_al:OASIcs.PPES.2011.1,
  author =	{Gebhard, Gernot and Cullmann, Christoph and Heckmann, Reinhold},
  title =	{{Software Structure and WCET Predictability}},
  booktitle =	{Bringing Theory to Practice: Predictability and Performance in Embedded Systems},
  pages =	{1--10},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-28-6},
  ISSN =	{2190-6807},
  year =	{2011},
  volume =	{18},
  editor =	{Lucas, Philipp and Wilhelm, Reinhard},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.PPES.2011.1},
  URN =		{urn:nbn:de:0030-drops-30836},
  doi =		{10.4230/OASIcs.PPES.2011.1},
  annote =	{Keywords: WCET Predictability, Embedded Software Structure, Coding Guidelines}
}
Document
Timing Anomalies Reloaded

Authors: Gernot Gebhard

Published in: OASIcs, Volume 15, 10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010)


Abstract
Computing tight WCET bounds in the presence of timing anomalies - found in almost any modern hardware architecture - is a major challenge of timing analysis. In this paper, we renew the discussion about timing anomalies, demonstrating that even simple hardware architectures are prone to timing anomalies. We furthermore complete the list of timing-anomalous cache replacement policies, proving that the most-recently-used replacement policy (MRU) also exhibits a domino effect.

Cite as

Gernot Gebhard. Timing Anomalies Reloaded. In 10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010). Open Access Series in Informatics (OASIcs), Volume 15, pp. 1-10, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2010)


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@InProceedings{gebhard:OASIcs.WCET.2010.1,
  author =	{Gebhard, Gernot},
  title =	{{Timing Anomalies Reloaded}},
  booktitle =	{10th International Workshop on Worst-Case Execution Time Analysis (WCET 2010)},
  pages =	{1--10},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-21-7},
  ISSN =	{2190-6807},
  year =	{2010},
  volume =	{15},
  editor =	{Lisper, Bj\"{o}rn},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2010.1},
  URN =		{urn:nbn:de:0030-drops-28201},
  doi =		{10.4230/OASIcs.WCET.2010.1},
  annote =	{Keywords: Timing Anomalies, Domino Effects, MRU Replacement Policy, LEON2}
}
Document
WCET Analysis for Preemptive Scheduling

Authors: Sebastian Altmeyer and Gernot Gebhard

Published in: OASIcs, Volume 8, 8th International Workshop on Worst-Case Execution Time Analysis (WCET'08) (2008)


Abstract
Hard real-time systems induce strict constraints on the timing of the task set. Validation of these timing constraints is thus a major challenge during the design of such a system. Whereas the derivation of timing guarantees must already be considered complex if tasks are running to completion, it gets even more complex if tasks are scheduled preemptively -- especially due to caches, deployed to improve the average performance. In this paper we propose a new method to compute valid upper bounds on a task's worst case execution time (WCET). Our method approximates an optimal memory layout such that the set of possibly evicted cache-entries during preemption is minimized. This set then delivers information to bound the execution time of tasks under preemption in an adopted WCET analysis.

Cite as

Sebastian Altmeyer and Gernot Gebhard. WCET Analysis for Preemptive Scheduling. In 8th International Workshop on Worst-Case Execution Time Analysis (WCET'08). Open Access Series in Informatics (OASIcs), Volume 8, pp. 1-8, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2008)


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@InProceedings{altmeyer_et_al:OASIcs.WCET.2008.1664,
  author =	{Altmeyer, Sebastian and Gebhard, Gernot},
  title =	{{WCET Analysis for Preemptive Scheduling}},
  booktitle =	{8th International Workshop on Worst-Case Execution Time Analysis (WCET'08)},
  pages =	{1--8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-10-1},
  ISSN =	{2190-6807},
  year =	{2008},
  volume =	{8},
  editor =	{Kirner, Raimund},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2008.1664},
  URN =		{urn:nbn:de:0030-drops-16644},
  doi =		{10.4230/OASIcs.WCET.2008.1664},
  annote =	{Keywords: WCET, Preemption}
}
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