diff -r a9f729b641a3 -r 1dc9bf9d016b src/hotspot/share/oops/instanceKlass.cpp
--- a/src/hotspot/share/oops/instanceKlass.cpp	Tue May 07 07:44:15 2019 +0200
+++ b/src/hotspot/share/oops/instanceKlass.cpp	Tue May 07 09:17:03 2019 +0200
@@ -2965,6 +2965,13 @@
 
 // On-stack replacement stuff
 void InstanceKlass::add_osr_nmethod(nmethod* n) {
+#ifndef PRODUCT
+  if (TieredCompilation) {
+      nmethod * prev = lookup_osr_nmethod(n->method(), n->osr_entry_bci(), n->comp_level(), true);
+      assert(prev == NULL || !prev->is_in_use(),
+      "redundunt OSR recompilation detected. memory leak in CodeCache!");
+  }
+#endif
   // only one compilation can be active
   {
     // This is a short non-blocking critical region, so the no safepoint check is ok.
@@ -3083,7 +3090,9 @@
     }
     osr = osr->osr_link();
   }
-  if (best != NULL && best->comp_level() >= comp_level && match_level == false) {
+
+  assert(match_level == false || best == NULL, "shouldn't pick up anything if match_level is set");
+  if (best != NULL && best->comp_level() >= comp_level) {
     return best;
   }
   return NULL;