Scope root = Scope::NewRootScope().ExitOnError();

  Node* write_0 = MakeWrite(root, "W0");
  Node* neutral_0 = MakeNeutral(root, "N0");
  Node* read_0 = MakeRead(root, "R0");
  Node* write_1 = MakeWrite(root, "W1");
  Node* neutral_1 = MakeNeutral(root, "N1");
  Node* read_1 = MakeRead(root, "R1");

  root.graph()->AddControlEdge(write_0, neutral_0);
  root.graph()->AddControlEdge(neutral_0, read_0);

// hold onto it for very long.
func mapaccess1(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
	if raceenabled && h != nil {
		callerpc := getcallerpc()
		pc := abi.FuncPCABIInternal(mapaccess1)
		racereadpc(unsafe.Pointer(h), callerpc, pc)
		raceReadObjectPC(t.Key, key, callerpc, pc)
	}
	if msanenabled && h != nil {
		msanread(key, t.Key.Size_)
	}
	if asanenabled && h != nil {
		asanread(key, t.Key.Size_)

              // not a TrustedFuture, call cancel directly.
              futureToPropagateTo.cancel(mayInterruptIfRunning);
            }
          }
          break;
        }
        // obj changed, reread
        localValue = abstractFuture.value;
        if (!(localValue instanceof SetFuture)) {
          // obj cannot be null at this point, because value can only change from null to non-null.

              // not a TrustedFuture, call cancel directly.
              futureToPropagateTo.cancel(mayInterruptIfRunning);
            }
          }
          break;
        }
        // obj changed, reread
        localValue = abstractFuture.value;
        if (!(localValue instanceof SetFuture)) {
          // obj cannot be null at this point, because value can only change from null to non-null.