[Bug tree-optimization/77479] New: [7 Regression] Compile time hog w/ -O2 (-Os)

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77479

            Bug ID: 77479
           Summary: [7 Regression] Compile time hog w/ -O2 (-Os)
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

(This issue was initially reported in PR72866.)

gcc 7.0.0-alpha20160821 and newer snapshots take large (or infinite?) time when
compiling the following reduced snippet at -O2 or -Os:

void
vr (int of, unsigned char bw)
{
  int d1;
  int lm = 0;

  for (d1 = 0; d1 < 3; ++d1)
    {
      const int vl = 2;

      while (bw < vl)
        {
        }
      if (bw != vl)
        lm -= vl;
    }
  while (++of < 1)
    {
      lm /= bw;
      of += lm;
    }
}

7.0.0-alpha20160731 seems to be unaffected by this issue.