src/share/vm/code/dependencies.cpp

@@ -880,10 +880,18 @@
   // Current thread must be in VM (not native mode, as in CI):
   assert(must_be_in_vm(), "raw oops here");
   // Must not move the class hierarchy during this check:
   assert_locked_or_safepoint(Compile_lock);
 
+  int nof_impls = instanceKlass::cast(context_type)->nof_implementors();
+  if (nof_impls > 1) {
+    // Avoid this case: *I.m > { A.m, C }; B.m > C
+    // %%% Until this is fixed more systematically, bail out.
+    // See corresponding comment in find_witness_anywhere.
+    return context_type;
+  }
+
   assert(!is_participant(new_type), "only old classes are participants");
   if (participants_hide_witnesses) {
     // If the new type is a subtype of a participant, we are done.
     for (int i = 0; i < num_participants(); i++) {
       klassOop part = participant(i);