diff -r 2251ba078bec -r eb7ce841ccec src/share/vm/opto/superword.cpp
--- a/src/share/vm/opto/superword.cpp	Sat Oct 24 16:18:50 2020 +0800
+++ b/src/share/vm/opto/superword.cpp	Sat Oct 24 16:43:47 2020 +0800
@@ -2209,21 +2209,13 @@
 //----------------------------get_pre_loop_end---------------------------
 // Find pre loop end from main loop.  Returns null if none.
 CountedLoopEndNode* SuperWord::get_pre_loop_end(CountedLoopNode* cl) {
-  Node* ctrl = cl->in(LoopNode::EntryControl);
-  if (!ctrl->is_IfTrue() && !ctrl->is_IfFalse()) return NULL;
-  Node* iffm = ctrl->in(0);
-  if (!iffm->is_If()) return NULL;
-  Node* bolzm = iffm->in(1);
-  if (!bolzm->is_Bool()) return NULL;
-  Node* cmpzm = bolzm->in(1);
-  if (!cmpzm->is_Cmp()) return NULL;
-  Node* opqzm = cmpzm->in(2);
-  // Can not optimize a loop if zero-trip Opaque1 node is optimized
-  // away and then another round of loop opts attempted.
-  if (opqzm->Opcode() != Op_Opaque1) {
+  // The loop cannot be optimized if the graph shape at
+  // the loop entry is inappropriate.
+  if (!PhaseIdealLoop::is_canonical_main_loop_entry(cl)) {
     return NULL;
   }
-  Node* p_f = iffm->in(0);
+
+  Node* p_f = cl->in(LoopNode::EntryControl)->in(0)->in(0);
   if (!p_f->is_IfFalse()) return NULL;
   if (!p_f->in(0)->is_CountedLoopEnd()) return NULL;
   CountedLoopEndNode* pre_end = p_f->in(0)->as_CountedLoopEnd();