[Bug tree-optimization/79622] New: [7 Regression] Wrong code w/ -O2 -floop-nest-optimize

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79622

            Bug ID: 79622
           Summary: [7 Regression] Wrong code w/ -O2 -floop-nest-optimize
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

At least gcc-7.0.0-alpha20170212 and gcc-7.0.0-alpha20170219 snapshots produce
wrong code for the following snippet w/ -O2 -floop-nest-optimize:

int bf;

int
main (void)
{
  int dc[5];

  for (bf = 0; bf < 2; ++bf)
    {
      int l9, g5 = -1;

      for (l9 = 0; l9 < 5; ++l9)
        {
          dc[l9] = g5;
          g5 = (dc[l9] > 0);
        }
    }

  if (dc[0] != -1)
    __builtin_abort ();

  return 0;
}

% gcc-7.0.0-alpha20170219 -O2 -o good dsmbs5u1.c
% ./good
% echo $?
0

% gcc-7.0.0-alpha20170219 -O2 -floop-nest-optimize -o bad dsmbs5u1.c
% ./bad
zsh: abort (core dumped)  ./bad