*** old/src/share/vm/opto/loopnode.cpp	Fri Mar 18 18:03:45 2016
--- new/src/share/vm/opto/loopnode.cpp	Fri Mar 18 18:03:44 2016

*** 3273,3282 ****
--- 3273,3317 ----
    }
    assert(!had_error, "bad dominance");
    return LCA;
  }
  
+ // Check the shape of the graph at the loop entry. In some cases,
+ // the shape of the graph does not match the shape outlined below.
+ // That is caused by the Opaque1 node "protecting" the shape of
+ // the graph being removed by, for example, the IGVN performed
+ // in PhaseIdealLoop::build_and_optimize().
+ //
+ // After the Opaque1 node has been removed, optimizations (e.g., split-if,
+ // loop unswitching, and IGVN, or a combination of them) can freely change
+ // the graph's shape. As a result, the graph shape outlined below cannot
+ // be guaranteed anymore.
+ bool PhaseIdealLoop::is_canonical_main_loop_entry(CountedLoopNode* cl) {
+   assert(cl->is_main_loop(), "check should be applied to main loops");
+   Node* ctrl = cl->in(LoopNode::EntryControl);
+   if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
+     return false;
+   }
+   Node* iffm = ctrl->in(0);
+   if (iffm == NULL || !iffm->is_If()) {
+     return false;
+   }
+   Node* bolzm = iffm->in(1);
+   if (bolzm == NULL || !bolzm->is_Bool()) {
+     return false;
+   }
+   Node* cmpzm = bolzm->in(1);
+   if (cmpzm == NULL || !cmpzm->is_Cmp()) {
+     return false;
+   }
+   Node* opqzm = cmpzm->in(2);
+   if (opqzm == NULL || opqzm->Opcode() != Op_Opaque1) {
+     return false;
+   }
+   return true;
+ }
+ 
  //------------------------------get_late_ctrl----------------------------------
  // Compute latest legal control.
  Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
    assert(early != NULL, "early control should not be NULL");