Omitting subject in AS & IF clauses

Can we omit "subject" in if clause and as clause ? For instance, If I go to the hotel, I will get buffet. Can I change into " If going to the hotel, I will get buffet" ? What about as clause ? I have so often seen the case of as clause where the subject is omitted. For example, "Their devotion to proper aims in life might have grown as have their facts.

Please teach me whether we can omit subject in if & as clauses or not.