--- old/src/share/vm/opto/graphKit.cpp	2015-08-12 14:09:36.000000000 +0200
+++ new/src/share/vm/opto/graphKit.cpp	2015-08-12 14:09:36.000000000 +0200
@@ -4185,6 +4185,7 @@
   Node* no_base = __ top();
   float likely  = PROB_LIKELY(0.999);
   float unlikely  = PROB_UNLIKELY(0.999);
+  Node* clean_card = __ ConI((jint)CardTableModRefBS::clean_card_val());
   Node* young_card = __ ConI((jint)G1SATBCardTableModRefBS::g1_young_card_val());
   Node* dirty_card = __ ConI((jint)CardTableModRefBS::dirty_card_val());
   Node* zeroX = __ ConX(0);
@@ -4242,17 +4243,23 @@
         // load the original value of the card
         Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw);
 
-        __ if_then(card_val, BoolTest::ne, young_card); {
-          sync_kit(ideal);
-          // Use Op_MemBarVolatile to achieve the effect of a StoreLoad barrier.
-          insert_mem_bar(Op_MemBarVolatile, oop_store);
-          __ sync_kit(this);
-
-          Node* card_val_reload = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw);
-          __ if_then(card_val_reload, BoolTest::ne, dirty_card); {
+        if (G1ElideMembar) {
+          __ if_then(card_val, BoolTest::eq, clean_card); {
             g1_mark_card(ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf);
           } __ end_if();
-        } __ end_if();
+        } else {
+          __ if_then(card_val, BoolTest::ne, young_card); {
+            sync_kit(ideal);
+            // Use Op_MemBarVolatile to achieve the effect of a StoreLoad barrier.
+            insert_mem_bar(Op_MemBarVolatile, oop_store);
+            __ sync_kit(this);
+
+            Node* card_val_reload = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw);
+            __ if_then(card_val_reload, BoolTest::ne, dirty_card); {
+              g1_mark_card(ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf);
+            } __ end_if();
+          } __ end_if();
+        }
       } __ end_if();
     } __ end_if();
   } else {