--- old/src/cpu/x86/vm/macroAssembler_x86.cpp	2017-02-23 13:57:10.553871135 +0100
+++ new/src/cpu/x86/vm/macroAssembler_x86.cpp	2017-02-23 13:57:10.453872120 +0100
@@ -5159,6 +5159,13 @@
   bind(done);
 }
 
+void MacroAssembler::clear_jweak_tag(Register possibly_jweak) {
+  const int32_t inverted_jweak_mask = ~static_cast<int32_t>(JNIHandles::weak_tag_mask);
+  STATIC_ASSERT(inverted_jweak_mask == -2); // otherwise check this code
+  // The inverted mask is sign-extended
+  andptr(possibly_jweak, inverted_jweak_mask);
+}
+
 //////////////////////////////////////////////////////////////////////////////////
 #if INCLUDE_ALL_GCS