[Bug tree-optimization/21488] [4.0/4.1 regression] Not copy propagating single-argument PHIs causes out-of-ssa coalescing failure

["pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-11 19:43 -------
Here is an example which shows that IV-OPTs is not the cause and that we have the same issue and 
shows what is going wrong clearer:
int k(int);
int h(void);
long h1(void);

int f(int i)
{
  int oldii;
  int ii;
  ii = h1();
  do
  {
    oldii = ii;
    k(ii);
    ii = oldii + h();
  } while (i<ii);
  return oldii;
}

We remove the use of oldii and use ii_n instead,  I think we are coalescing the wrong two ii_n and not 
the two inside the loop but the one that was called oldii with the one before the loop.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21488