UD-chains for record fields

Thu, 4 Oct 90 18:01:29 +0100

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UD-chains for record fields jml@wally.altair.fr (1990-10-04)
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Newsgroups: comp.compilers
From: jml@wally.altair.fr
Posted-Date: Thu, 4 Oct 90 18:01:29 +0100
Keywords: optimize
Organization: Compilers Central
Date: Thu, 4 Oct 90 18:01:29 +0100

  I wonder if there has been any research done on the behavior of
records in dataflow analysis. What I mean is that the algorithms
for the building of ud-chains or alias analysis that I have read
about consider only simple variables and arrays. But field
selection also introduces aliasing. For example, after an
assignment such as
      x.a = v;
v.b becomes an alias for x.a.b.

  And when pointer-induced aliasing is compounded with field
selection, it seems to lead to rather formidable complexity:
      s1: y = x;
      s2: y->a = v;
      s3: return (x->a.b);

  There seems to be no definition of x->a.b reaching s3, though s2
is such a definition, due to aliasing of x to y in s1, even if
the field b does not appear explicitly in s2.

  I'd be grateful if somebody could direct me to literature
on this problem.
Jean-Marie (John) Larcheveque
<jml@bdblues.altair.fr> or <jml@nuri.inria.fr>

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