diff -r f33e2b727e10 -r 4373df7c4a92 src/share/vm/opto/loopnode.cpp
--- a/src/share/vm/opto/loopnode.cpp	Fri Apr 24 04:23:06 2020 +0100
+++ b/src/share/vm/opto/loopnode.cpp	Mon Mar 23 19:52:34 2020 +0800
@@ -1538,7 +1538,7 @@
   // If I am a shared header (multiple backedges), peel off the many
   // backedges into a private merge point and use the merge point as
   // the one true backedge.
-  if( _head->req() > 3 ) {
+  if (_head->req() > 3 && !_irreducible) {
     // Merge the many backedges into a single backedge but leave
     // the hottest backedge as separate edge for the following peel.
     merge_many_backedges( phase );