src/share/vm/opto/graphKit.cpp

rev 10106 : 8087341: C2 doesn't optimize redundant memory operations with G1
Summary: effect of memory barrier in post barrier is too wide
Reviewed-by: duke

*** 3147,3156 ****
--- 3147,3169 ----
      set_memory(_gvn.transform(new ProjNode(membar, TypeFunc::Memory)),alias_idx);
    }
    return membar;
  }
  
+ void GraphKit::insert_store_load_for_barrier() {
+   Node* mem = reset_memory();
+   MemBarNode* mb = MemBarNode::make(C, Op_MemBarVolatile, Compile::AliasIdxBot);
+   mb->init_req(TypeFunc::Control, control());
+   mb->init_req(TypeFunc::Memory, mem);
+   Node* membar = _gvn.transform(mb);
+   set_control(_gvn.transform(new ProjNode(membar, TypeFunc::Control)));
+   Node* newmem = _gvn.transform(new ProjNode(membar, TypeFunc::Memory));
+   set_all_memory(mem);
+   set_memory(newmem, Compile::AliasIdxRaw);
+ }
+ 
+ 
  //------------------------------shared_lock------------------------------------
  // Emit locking code.
  FastLockNode* GraphKit::shared_lock(Node* obj) {
    // bci is either a monitorenter bc or InvocationEntryBci
    // %%% SynchronizationEntryBCI is redundant; use InvocationEntryBci in interfaces
*** 3838,3848 ****
    int adr_type = Compile::AliasIdxRaw;
    Node*   zero = __ ConI(0); // Dirty card value
    BasicType bt = T_BYTE;
  
    if (UseConcMarkSweepGC && UseCondCardMark) {
!     insert_mem_bar(Op_MemBarVolatile);   // StoreLoad barrier
      __ sync_kit(this);
    }
  
    if (UseCondCardMark) {
      // The classic GC reference write barrier is typically implemented
--- 3851,3861 ----
    int adr_type = Compile::AliasIdxRaw;
    Node*   zero = __ ConI(0); // Dirty card value
    BasicType bt = T_BYTE;
  
    if (UseConcMarkSweepGC && UseCondCardMark) {
!     insert_store_load_for_barrier();
      __ sync_kit(this);
    }
  
    if (UseCondCardMark) {
      // The classic GC reference write barrier is typically implemented
*** 4278,4289 ****
          // 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); {
              g1_mark_card(ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf);
--- 4291,4301 ----
          // 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);
!           insert_store_load_for_barrier();
            __ 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);