Warner Bros. has signed on to become the first Hollywood studio to distribute a movie starring wacko Mel Gibson in seven years. Warners has bought North American rights to Martin Campell’s “Edge of Darkness,” an independently-financed thriller he shot in Boston last year. Gibson plays a cop whose daughter is murdered; his investigation uncovers systemic corruption that led to her death. It’s Mel’s first starring role since M. Night’s Shyamalan’s “Signs” in 2002. Gibson, once one of the biggest stars in the business, since directed two movies, the hugely popular if controversial “The Passion of the Christ” and the less successful “Apocalypto.” But Mel’s also been dogged by accusations of anti-Semitism stemming from the former film’s depiction of Jews and his remarks during a drunk-driving arrest. No release date was given for “Edge of Darkness,” which was co-scripted by William Monahan (“The Departed”) and is based on a U.K. mini-series. Meanwhile, Variety is also reporting — I’m sure his new agent has nothing to with planting this story — that five studios are circling Mel’s fellow wacko Tom Cruise, who has also had his share of public-relations problems. Supposedly studio suits are encouraged that “Valkyrie,” which grossed $82 million stateside, wasn’t a total disaster, though it’s only covered a fraction of its reported $90 million budget and $20 million promotional budget. The only film Cruise is actually “attached” to at this point is “The Mantarese Circle,” a Robert Ludlum novel being adapted by director David Cronenberg. This project, which may co-star Denzel Washington, is at MGM. Curiously un-mentioned is Cruise’s supposed role as titular head of MGM subsidiary United Artists.