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DOI: 10.4230/OASIcs.WCET.2015.85

Analysing Switch-Case Code with Abstract Execution

Authors: Niklas Holsti, Jan Gustafsson, Linus Källberg, and Björn Lisper

Published in: OASIcs, Volume 47, 15th International Workshop on Worst-Case Execution Time Analysis (WCET 2015)

Abstract

Constructing the control-flow graph (CFG) of machine code is made difficult by dynamic transfers of control (DTC), where the address of the next instruction is computed at run-time. Switchcase statements make compilers generate a large variety of machine-code forms with DTC. Two analysis approaches are commonly used: pattern-matching methods identify predefined instruction patterns to extract the target addresses, while analytical methods try to compute the set of target addresses using a general value-analysis. We tested the abstract execution method of the SWEET tool as a value analysis for switch-case code. SWEET is here used as a plugin to the Bound-T tool: thus our work can also be seen as an experiment in modular tool design, where a general value-analysis tool is used to aid the CFG construction in a WCET analysis tool. We find that the abstract-execution analysis works at least as well as the switch-case analyses in Bound-T itself, which are mostly based on pattern-matching. However, there are still some weaknesses: the abstract domains available in SWEET are not well suited to representing sets of DTC target addresses, which are small but sparse and irregular. Also, in some cases the abstract-execution analysis fails because the used domain is not relational, that is, does not model arithmetic relationships between the values of different variables. Future work will be directed towards the design of abstract domains eliminating these weaknesses.

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Niklas Holsti, Jan Gustafsson, Linus Källberg, and Björn Lisper. Analysing Switch-Case Code with Abstract Execution. In 15th International Workshop on Worst-Case Execution Time Analysis (WCET 2015). Open Access Series in Informatics (OASIcs), Volume 47, pp. 85-94, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{holsti_et_al:OASIcs.WCET.2015.85,
  author =	{Holsti, Niklas and Gustafsson, Jan and K\"{a}llberg, Linus and Lisper, Bj\"{o}rn},
  title =	{{Analysing Switch-Case Code with Abstract Execution}},
  booktitle =	{15th International Workshop on Worst-Case Execution Time Analysis (WCET 2015)},
  pages =	{85--94},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-95-8},
  ISSN =	{2190-6807},
  year =	{2015},
  volume =	{47},
  editor =	{Cazorla, Francisco J.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2015.85},
  URN =		{urn:nbn:de:0030-drops-52598},
  doi =		{10.4230/OASIcs.WCET.2015.85},
  annote =	{Keywords: ynamic control flow, indexed branch, machine-code analysis, WCET analysis}
}

Document

DOI: 10.4230/OASIcs.WCET.2009.2279

ALF - A Language for WCET Flow Analysis

Authors: Jan Gustafsson, Andreas Ermedahl, Björn Lisper, Christer Sandberg, and Linus Källberg

Published in: OASIcs, Volume 10, 9th International Workshop on Worst-Case Execution Time Analysis (WCET'09) (2009)

Abstract

Static Worst-Case Execution Time (WCET) analysis derives upper bounds for the execution times of programs. Such bounds are crucial when designing and verifying real-time systems. A key component in static WCET analysis is the flow analysis, which derives bounds on the number of times different code entities can be executed. Examples of flow information derived by a flow analysis are loop bounds and infeasible paths. Flow analysis can be performed on source code, intermediate code, or binary code: for the latter, there is a proliferation of instruction sets. Thus, flow analysis must deal with many code formats. However, the basic flow analysis techniques are more or less the same regardless of the code format. Thus, an interesting option is to define a common code format for flow analysis, which also allows for easy translation from the other formats. Flow analyses for this common format will then be portable, in principle supporting all types of code formats which can be translated to this format. Further, a common format simplifies the development of flow analyses, since only one specific code format needs to be targeted. This paper presents such a common code format, the ALF language (ARTIST2 Language for WCET Flow Analysis).

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Jan Gustafsson, Andreas Ermedahl, Björn Lisper, Christer Sandberg, and Linus Källberg. ALF - A Language for WCET Flow Analysis. In 9th International Workshop on Worst-Case Execution Time Analysis (WCET'09). Open Access Series in Informatics (OASIcs), Volume 10, pp. 1-11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2009)

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@InProceedings{gustafsson_et_al:OASIcs.WCET.2009.2279,
  author =	{Gustafsson, Jan and Ermedahl, Andreas and Lisper, Bj\"{o}rn and Sandberg, Christer and K\"{a}llberg, Linus},
  title =	{{ALF - A Language for WCET Flow Analysis}},
  booktitle =	{9th International Workshop on Worst-Case Execution Time Analysis (WCET'09)},
  pages =	{1--11},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-14-9},
  ISSN =	{2190-6807},
  year =	{2009},
  volume =	{10},
  editor =	{Holsti, Niklas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2009.2279},
  URN =		{urn:nbn:de:0030-drops-22791},
  doi =		{10.4230/OASIcs.WCET.2009.2279},
  annote =	{Keywords: WCET analysis, flow analysis, ALF WCET analysis, flow analysis, ALF}
}

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Analysing Switch-Case Code with Abstract Execution

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ALF - A Language for WCET Flow Analysis

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