[Bug tree-optimization/81240] New: [7/8 Regression] ICE in dfs_enumerate_from

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81240

            Bug ID: 81240
           Summary: [7/8 Regression] ICE in dfs_enumerate_from
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc 7.1 and gcc-8.0.0-alpha20170625 snapshot ICE when compiling the following
snippet w/ -O2 (-O3, -Ofast):

void
py (int y7, int vh)
{
  const int kq = 2;
  int rn;

  y7 = rn = -1;
  for (;;)
  {
    int w6;

    for (w6 = 0; w6 < kq; ++w6)
    {
      int xk = !!y7 - ((vh != 0) ? 1 : y7);

      if (xk != 0)
      {
        vh = 0;
        while (vh < kq)
        {
          w6 = 1;
          vh += !!(rn - w6) + 1;
          rn *= 2;
          if (rn != 0)
            w6 = kq;
        }
      }
    }

    if (rn != 0)
      for (;;)
      {
      }

    y7 = 0;
  }
}

% gcc-8.0.0-alpha20170625 -O2 -ftracer -c -w pniq8oa3.c
during GIMPLE pass: vrp
pniq8oa3.c: In function 'py':
pniq8oa3.c:2:1: internal compiler error: in dfs_enumerate_from, at
cfganal.c:1194
 py (int y7, int vh)
 ^~