--- old/src/cpu/x86/vm/shenandoahBarrierSetAssembler_x86.cpp	2019-10-28 20:26:19.661486431 +0100
+++ new/src/cpu/x86/vm/shenandoahBarrierSetAssembler_x86.cpp	2019-10-28 20:26:19.569486436 +0100
@@ -63,10 +63,15 @@
   bool borrow_reg = (tmp == noreg);
   if (borrow_reg) {
     // No free registers available. Make one useful.
-    tmp = rscratch1;
+    tmp = LP64_ONLY(rscratch1) NOT_LP64(rdx);
+    if (tmp == dst) {
+      tmp = LP64_ONLY(rscratch2) NOT_LP64(rcx);
+    }
     __ push(tmp);
   }
 
+  assert_different_registers(dst, tmp);
+
   Label done;
   __ movptr(tmp, Address(dst, oopDesc::mark_offset_in_bytes()));
   __ notptr(tmp);