“All of You” is set in a slightly futuristic society whose technological and society-altering centerpiece seems to be a test that can positively identify each person’s true soulmate. A pair of longtime platonic friends played by Brett Goldstein and Imogen Poots have differing opinions about the test – she wants to take it, he thinks it’s ridiculous – but in the opening scene, he gives her the money to do it, and by doing so sets the story in motion.

And from that moment on, the soulmate test is pretty much irrelevant to “All of You,” which premiered this week at the Toronto International Film Festival. It’s a classic cinematic MacGuffin, important to get things going and insignificant to what happens from that point on, which turns out to be a decades-spanning, vaguely “When Harry Met Sally”-style story of a friendship that could be something more if the...