[Bug middle-end/67005] [5/6 Regression] ICE: in verify_loop_structure, at cfgloop.c:1647 (loop with header n not in loop tree)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67005

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Hm, adding || (e2->flags & EDGE_IRREDUCIBLE_LOOP) doesn't work; the E2 edge
doesn't have the EDGE_IRREDUCIBLE_LOOP flag, even if I recompute that flag via
mark_irreducible_loops.  So maybe set LOOPS_NEED_FIXUP every time we remove an
edge?

FTR, the CFG looks like

f ()
{
  int a.0_4;
  int a.0_7;

  <bb 2>:
  a.0_4 = a;
  if (a.0_4 == 0)
    goto <bb 3> (lbl);
  else
    goto <bb 4>;

lbl:

  <bb 4>:
  a.0_7 = a;
  if (a.0_7 != 0)
    goto <bb 5>;
  else
    goto <bb 3> (lbl);

  <bb 5>:
  a = 8;
  goto <bb 3> (lbl);

}

so the 2 -> 4 and 2 -> 3 edges are multiple entries of a loop -- why aren't
they EDGE_IRREDUCIBLE_LOOP?