src/hotspot/share/opto/compile.cpp

@@ -1645,10 +1645,14 @@
        if (flat->offset() == TypePtr::OffsetBot) {
          alias_type(idx)->set_element(flat->is_aryptr()->elem());
        }
      }
      if (flat->isa_klassptr()) {
+       if (UseCompactObjectHeaders) {
+         if (flat->offset() == in_bytes(Klass::prototype_header_offset()))
+           alias_type(idx)->set_rewritable(false);
+       }
        if (flat->offset() == in_bytes(Klass::super_check_offset_offset()))
          alias_type(idx)->set_rewritable(false);
        if (flat->offset() == in_bytes(Klass::modifier_flags_offset()))
          alias_type(idx)->set_rewritable(false);
        if (flat->offset() == in_bytes(Klass::access_flags_offset()))