Irrevocablet

What is the cost basis for the real estate asset when it is transferred into the irrevocable trust? Is it the fair market value for the property at the time of transfer? Since the property is transferred to the irrevocable trust, the real estate tax benefit of $250k/$500 (single/joint owner) deduction is lost. How does having an irrevocable trust address this? Is the cost basis the method to reduce capital gains taxes?