G1GC-CardMark.cpp

// CPP, OpenJDK C2 compiler style... this is from:
// http://hg.openjdk.java.net/jdk9/jdk9/hotspot/file/b756e7a2ec33/src/share/vm/opto/graphKit.cpp#l4285
void GraphKit::g1_write_barrier_post(Node* oop_store,
                                     Node* obj,
                                     Node* adr,
                                     uint alias_idx,
                                     Node* val,
                                     BasicType bt,
                                     bool use_precise) {
/// ... Loads of other crap here...

// if (xor_res == 0) same region so skip
__ if_then(xor_res, BoolTest::ne, zeroX); {

  // No barrier if we are storing a NULL
  __ if_then(val, BoolTest::ne, null(), unlikely); {

    // Ok must mark the card if not already dirty

    // 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); // !!!HELLO THERE!!!
      __ 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();

// ... And some more crap later too...
}