--- old/src/hotspot/share/opto/c2compiler.cpp	2018-08-20 11:53:35.252419252 +0100
+++ new/src/hotspot/share/opto/c2compiler.cpp	2018-08-20 11:53:34.962418388 +0100
@@ -547,6 +547,12 @@
 #endif
   case vmIntrinsics::_currentTimeMillis:
   case vmIntrinsics::_nanoTime:
+    break;
+  case vmIntrinsics::_writeback0:
+  case vmIntrinsics::_writebackPreSync0:
+  case vmIntrinsics::_writebackPostSync0:
+    if (getenv("DISABLE_UNSAFE_WRITEBACK_INTRINSIC")) return false;
+    break;
   case vmIntrinsics::_allocateInstance:
   case vmIntrinsics::_allocateUninitializedArray:
   case vmIntrinsics::_newArray: