--- a/src/share/vm/opto/library_call.cpp	Tue Sep 22 23:47:24 2015 +0200
+++ b/src/share/vm/opto/library_call.cpp	Thu Sep 24 12:49:23 2015 +0200
@@ -2697,6 +2697,7 @@
   // For now, we handle only those cases that actually exist: ints,
   // longs, and Object. Adding others should be straightforward.
   Node* load_store;
+  Node* result;
   switch(type) {
   case T_INT:
     if (kind == LS_xadd) {
@@ -2708,6 +2709,7 @@
     } else {
       ShouldNotReachHere();
     }
+    result = load_store;
     break;
   case T_LONG:
     if (kind == LS_xadd) {
@@ -2719,6 +2721,7 @@
     } else {
       ShouldNotReachHere();
     }
+    result = load_store;
     break;
   case T_OBJECT:
     // Transformation of a value which could be NULL pointer (CastPP #NULL)
@@ -2765,6 +2768,7 @@
         load_store = _gvn.transform(new CompareAndSwapNNode(control(), mem, adr,
                                                                 newval_enc, oldval_enc));
       }
+      result = load_store;
     } else
 #endif
     {
@@ -2773,11 +2777,13 @@
       } else {
         assert(kind == LS_cmpxchg, "wrong LoadStore operation");
         load_store = _gvn.transform(new CompareAndSwapPNode(control(), mem, adr, newval, oldval));
+	result = load_store;
 
         if (UseShenandoahGC) {
-          set_control(load_store);
           // if (! success)
-          IfNode* iff = create_and_map_if(control(), load_store, PROB_UNKNOWN, COUNT_UNKNOWN);
+	  Node* cmp_true = _gvn.transform(new CmpINode(load_store, intcon(1)));
+	  Node* tst_true = _gvn.transform(new BoolNode(cmp_true, BoolTest::eq));
+          IfNode* iff = create_and_map_if(control(), tst_true, PROB_LIKELY_MAG(2), COUNT_UNKNOWN);
           Node* iftrue = _gvn.transform(new IfTrueNode(iff));
           Node* iffalse = _gvn.transform(new IfFalseNode(iff));
 
@@ -2821,20 +2827,20 @@
                                          NULL,
                                          adr, newval, current);
 
-          Node* result = _gvn.transform(new ProjNode(call, TypeFunc::Parms + 0));
+          Node* retval = _gvn.transform(new ProjNode(call, TypeFunc::Parms + 0));
 
           region->init_req(_shenandoah_path, control());
-          phi   ->init_req(_shenandoah_path, result);
+          phi   ->init_req(_shenandoah_path, retval);
 
           set_control(_gvn.transform(region));
           record_for_igvn(region);
           phi = _gvn.transform(phi);
-          load_store = phi;
+	  result = phi;
         }
 
       }
     }
-    post_barrier(control(), load_store, base, adr, alias_idx, newval, T_OBJECT, true);
+    post_barrier(control(), result, base, adr, alias_idx, newval, T_OBJECT, true);
     break;
   default:
     fatal(err_msg_res("unexpected type %d: %s", type, type2name(type)));
@@ -2850,7 +2856,7 @@
   if (type == T_OBJECT && kind == LS_xchg) {
 #ifdef _LP64
     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
-      load_store = _gvn.transform(new DecodeNNode(load_store, load_store->get_ptr_type()));
+      result = _gvn.transform(new DecodeNNode(result, result->get_ptr_type()));
     }
 #endif
     if (can_move_pre_barrier()) {
@@ -2859,7 +2865,7 @@
       // gets inserted between them.
       pre_barrier(false /* do_load */,
                   control(), NULL, NULL, max_juint, NULL, NULL,
-                  load_store /* pre_val */,
+                  result /* pre_val */,
                   T_OBJECT);
     }
   }
@@ -2868,8 +2874,8 @@
   insert_mem_bar(Op_MemBarCPUOrder);
   insert_mem_bar(Op_MemBarAcquire);
 
-  assert(type2size[load_store->bottom_type()->basic_type()] == type2size[rtype], "result type should match");
-  set_result(load_store);
+  assert(type2size[result->bottom_type()->basic_type()] == type2size[rtype], "result type should match");
+  set_result(result);
   return true;
 }