src/hotspot/share/runtime/arguments.cpp

@@ -2096,16 +2096,23 @@
     FLAG_SET_CMDLINE(bool, ValueTypeReturnedAsFields, false);
     warning("ValueTypeReturnedAsFields is not supported on this platform");
   }
 
   if (EnableValhalla) {
-    // C1 has no support for value types
+    if (!EnableValhallaC1) {
+      // C1 support for value types is incomplete. Don't use it by default.
     if (!FLAG_IS_DEFAULT(TieredCompilation)) {
       warning("TieredCompilation disabled because value types are not supported by C1");
     }
     FLAG_SET_CMDLINE(bool, TieredCompilation, false);
   } else {
+      if (TieredStopAtLevel > 1) {
+        warning("C1 doesn't work with C2 yet. Forcing TieredStopAtLevel=1");
+        FLAG_SET_CMDLINE(intx, TieredStopAtLevel, 1);
+      }
+    }
+  } else {
     FLAG_SET_CMDLINE(bool, ValueArrayFlatten, false);
   }
 
   return status;
 }