Swan Song, which is set in an eerily near future, tells the story of Cameron, who after receiving a terminal diagnosis has to decide whether to tell his family or quietly replace himself with a clone.

Ali - who won his Academy Awards for performances in Green Book and Moonlight, and also starred in the hit series True Detective - plays both Cameron and his clone, named Jack, and says inhabiting both roles took its toll.

"I think acting in general, it takes a bit out of you, it really does," the star told Sky News. "It reminded me of True Detective a bit. When I did True Detective there are three different eras I was playing, so one moment I'd be 35 and several hours later I was playing 80, 75 years old, or what have you.

"Being in that spin-cycle, so to speak, is a little bit dizzying."

Ali credits writer-director Ben Cleary for making his job manageable. The Irish film-maker caught the industry's attention by winning his own Oscar in 2016 for the live action short film Stutterer.

"Ben did such a wonderful job - even in scenes where one moment I'm playing Cameron and then there's a quick change, quick, quick costume change and some make-up alterations, and then I'm hopping into Jack's shoes," Ali said.

"The characters are so clearly drafted where they want different things, that I always felt really safe and clear as to who I was playing and what I needed to try to do and accomplish in the scene. So that's a huge testament to Ben making that all manageable and doable."

There's no watching Swan Song, which also stars Naomie Harris, Awkwafina and Glenn Close, without wondering how you would react in the same situation.

Ali says the idea of stimulating conversation and debate in audiences is extremely gratifying.

"If we are accomplishing that while people are watching the film, I think that that's a big deal because we live in a world right now that is full of opportunities to be entertained," he said.

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"So if you are able to capture people for a moment, grab their attention and then leave them thinking or questioning or having conversations about what they just experienced with you, that is a real goal. And I know it's something that's really difficult in this time because there's a lot of great stuff out there right now."

Swan Song looks at what it is to be real, and questions what makes us who we are.

Ali says the idea of human cloning is not one he's "particularly comfortable with" but says he does appreciate the underlying messages about living up to our potential.

"Jack doesn't have the same illnesses Cameron has, but he is Cameron, and so you begin to see Jack in some way make decisions and take advantage of the moment in time in a way that Cameron wasn't necessarily taking advantage.

"We all have that capacity to think about who we are at our potential, who's our highest self, so to speak, and begin to try to work towards that, take stock of anywhere in our life where we don't feel fulfilled, changes that we need to make and act on that.

"We don't necessarily need a death sentence to go, 'Oh, I'm going to start living to my fullest', I think part of the message in this story is to do that right now."

Swan Song is out now on Apple TV+