--- old/src/cpu/x86/vm/jniFastGetField_x86_64.cpp	2017-04-25 16:43:54.119176617 +0200
+++ new/src/cpu/x86/vm/jniFastGetField_x86_64.cpp	2017-04-25 16:43:53.983176622 +0200
@@ -81,7 +81,8 @@
                                                 // robj is data dependent on rcounter.
   }
 
-  __ clear_jweak_tag(robj);
+  __ testb(robj, JNIHandles::weak_tag_mask);
+  __ jcc (Assembler::notZero, slow);
 
   __ movptr(robj, Address(robj, 0));             // *obj
   __ mov   (roffset, c_rarg2);
@@ -182,7 +183,8 @@
                                                 // robj is data dependent on rcounter.
   }
 
-  __ clear_jweak_tag(robj);
+  __ testb(robj, JNIHandles::weak_tag_mask);
+  __ jcc (Assembler::notZero, slow);
 
   __ movptr(robj, Address(robj, 0));             // *obj
   __ mov   (roffset, c_rarg2);