[Bug tree-optimization/36387] New: points-to variables not transitively clobbered

[rguenth at gcc dot gnu dot org]

Call clobbering doesn't transitively close the pointed-to sets.

This blocks removal of call-clobbering of variables that have their addresses
stored in local structures.

This also generates wrong code for (-O2 {,-fno-tree-sra} - dependent on
the amount of fixes installed)

extern void abort (void);
struct Foo {
    int *p;
};
struct Bar {
    struct Foo *x;
    int *q;
};
struct Foo __attribute__((noinline))
bar(int *p)
{
  struct Foo f;
  f.p = p;
  return f;
}
void __attribute__((noinline))
foo(struct Foo f)
{
  *f.p = 0;
}
int main()
{
  int a, b;
  a = 0;
  b = 1;
  struct Bar f;
  struct Foo g = bar (&b);
  f.x = &g;
  f.q = &a;
  foo(*f.x);
  if (b != 0)
    abort ();
  return 0;
}


-- 
           Summary: points-to variables not transitively clobbered
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Keywords: wrong-code, alias
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36387