I'm pretty sure he wouldn't have performed Wet dreams. He could have did the song he performed on letterman Be Free, or one of his older songs that talk about similar subjects. Off of his last album, he could have done Tale of 2 cities, Love yours, apparently (he was nominated for performing that song, so he could have performed it there). He has lots of songs to pick from. Just like kendrick has lots of songs to pick from. Kendrick didn't go up there performing swimming pools or bytch don't kill my vibe.
Also, the song doesn't have to be about something serious. For example, Drunk in Love was performed on there not too long ago. Taylor swift little pop songs. Brittney Spears. & the list goes on.