Despite his looks and charm and willingness to occasionally join the summer-blockbuster parade, Jake Gyllenhaal knows when not to act like a star. In the underrated drama End of Watch, Gyllenhaal, 32, created a wistful, kind, often afraid, and effortlessly funny young cop, and he calibrated the performance to ride alongside the excellent Michael Peña, as his partner. It’s a violent, gritty movie, but the scenes in which the buddies riff on each other as they go about their rounds, landing in and out of danger, are the best parts; they tell you just about everything there is to know about male friendship. Gyllenhaal also made his New York stage debut in the play If There Is I Haven’t Found It Yet, as an aimless chatterbox with a shaggy beard, a very convincing British accent, and a reluctance to grow up. With his skittish, staggering performance, Gyllenhaal made the most (but never too much) of a supporting role. He provided the laughs, and the audience witnessed the action — involving a family drowning in regret — largely through his enormous, doleful eyes.