src/share/vm/opto/graphKit.cpp

rev 5127 : 8023597: Optimize G1 barriers code for unsafe load_store
Summary: Avoid loading old values in G1 pre-barriers for inlined unsafe load_store nodes.

*** 1499,1508 ****
--- 1499,1527 ----
        ShouldNotReachHere();
  
    }
  }
  
+ bool GraphKit::can_move_pre_barrier() const {
+   BarrierSet* bs = Universe::heap()->barrier_set();
+   switch (bs->kind()) {
+     case BarrierSet::G1SATBCT:
+     case BarrierSet::G1SATBCTLogging:
+       return true; // Can move it if no safepoint
+ 
+     case BarrierSet::CardTableModRef:
+     case BarrierSet::CardTableExtension:
+     case BarrierSet::ModRef:
+       return true; // There is no pre-barrier
+ 
+     case BarrierSet::Other:
+     default      :
+       ShouldNotReachHere();
+   }
+   return false;
+ }
+ 
  void GraphKit::post_barrier(Node* ctl,
                              Node* store,
                              Node* obj,
                              Node* adr,
                              uint  adr_idx,
*** 3549,3558 ****
--- 3568,3579 ----
      assert(pre_val == NULL, "loaded already?");
      assert(val_type != NULL, "need a type");
    } else {
      // In this case both val_type and alias_idx are unused.
      assert(pre_val != NULL, "must be loaded already");
+     // Nothing to be done if pre_val is null.
+     if (pre_val->bottom_type() == TypePtr::NULL_PTR) return;
      assert(pre_val->bottom_type()->basic_type() == T_OBJECT, "or we shouldn't be here");
    }
    assert(bt == T_OBJECT, "or we shouldn't be here");
  
    IdealKit ideal(this, true);