// Uses, not Users, in case getUsers ever dedups.
      for (OpOperand& operand : value.getUses()) {
        Operation* user = ancestor[operand.getOwner()];
        remaining_incoming_data_edges[user]--;
        if (remaining_incoming_data_edges[user] == 0 &&
            remaining_incoming_ctrl_edges[user] == 0) {
          ready.push_back(user);
        }
      }
    }

    // Find the "best" operation to emit. We