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Asian Symposium on Programming Languages and Systems

APLAS 2011: Programming Languages and Systems pp 137–154Cite as

A Non-iterative Data-Flow Algorithm for Computing Liveness Sets in Strict SSA Programs

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Part of the book series: Lecture Notes in Computer Science ((LNPSE,volume 7078))

Abstract

We revisit the problem of computing liveness sets (the sets of variables live-in and live-out of basic blocks) for programs in strict static single assignment (SSA). In strict SSA, aka SSA with dominance property, the definition of a variable always dominates all its uses. We exploit this property and the concept of loop-nesting forest to design a fast two-phases data-flow algorithm: a first pass traverses the control-flow graph (CFG), propagating liveness information backwards, a second pass traverses a loop-nesting forest, updating liveness sets within loops. The algorithm is proved correct even for irreducible CFGs. We analyze its algorithmic complexity and evaluate its efficiency on SPECINT 2000. Compared to traditional iterative data-flow approaches, which perform updates until a fixed point is reached, our algorithm is 2 times faster on average. Other approaches are possible that propagate from uses to definitions, one variable at a time, instead of unioning sets as in data-flow analysis. Our algorithm is 1.43 times faster than the fastest alternative on average, when sets are represented as bitsets and for optimized programs, which have non-trivial live-ranges and a larger number of variables.

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Author information

Authors and Affiliations

  1. LIP, UMR 5668 CNRS, INRIA, ENS-Lyon, UCB-Lyon, France

    Benoit Boissinot, Florian Brandner, Alain Darte & Fabrice Rastello

  2. Kalray, France

    Benoît Dupont de Dinechin

Authors
  1. Benoit Boissinot
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  2. Florian Brandner
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  3. Alain Darte
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  4. Benoît Dupont de Dinechin
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  5. Fabrice Rastello
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Editor information

Editors and Affiliations

  1. Department of Computer Science, University of Oxford, Parks Road, OX1 3QD, Oxford, UK

    Hongseok Yang

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Boissinot, B., Brandner, F., Darte, A., de Dinechin, B.D., Rastello, F. (2011). A Non-iterative Data-Flow Algorithm for Computing Liveness Sets in Strict SSA Programs. In: Yang, H. (eds) Programming Languages and Systems. APLAS 2011. Lecture Notes in Computer Science, vol 7078. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-25318-8_13

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  • DOI: https://doi.org/10.1007/978-3-642-25318-8_13

  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-642-25317-1

  • Online ISBN: 978-3-642-25318-8

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