Up-and-coming thesp Mackenzie Davis, whose performance in Drake Doremus’ Sundance pic “Breathe In” is earning buzz in advance of the festival, is set to join Zac Efron and Miles Teller in the indie movie “Are We Officially Dating?”Tom Gormican is writing and directing the romantic comedy, which Treehouse Pictures’ Justin Nappi and Kevin Turen are producing with Scott Aversano and Andrew O’Connor. QED Intl. is handling international sales. Gormican’s script, which appeared on the 2010 Black List, follows three male friends in Manhattan who make a pact to remain single just as each starts to fall in love. Davis replaces Deborah Ann Woll in the pic, which co-stars Imogen Poots and Michael B. Jordan. Thesp will play the ex-wife of one of the three leads. Davis, who appeared in James Ponsoldt’s “Smashed,” recently wrapped Michael Dowse’s romantic comedy “The F Word,” which stars Daniel Radcliffe and Zoe Kazan. She’s due to break out at Sundance with a key role as Guy Pearce and Amy Ryan’s daughter in Doremus’ “Breathe In,” which is expected to be a hot acquisition title. Davis is repped by UTA and Thruline Entertainment.