Faster by removing variables - Original and optimised Swift (optimised is 30-40% faster

pointless swift benchmarks

import Foundation

private let testSize = 100_000_000
private var testTime:CFAbsoluteTime = 0
private var optimisedTestTime:CFAbsoluteTime = 0

class Test
{
    func testing2(var x : Int) -> Int
    {
        if x % 3 == 0 {
            x += 10
        }
        x++
        return x
    }
    
    func test()
    {
        var time = NSDate.timeIntervalSinceReferenceDate();
        var x = 0;
        for (var i = 0; i < testSize; i++)
        {
            x = testing2(x)
        }
        let time2 = NSDate.timeIntervalSinceReferenceDate() - time
        NSLog("Original: %i in %f seconds", x, time2)
        testTime = time2
    }
}

Test().test()


final class OptimisedTest
{
    func testing2(x : Int) -> Int
    {
        return x % 3 == 0 ? x + 11 : x + 1
    }
    
    func test()
    {
        let time = CFAbsoluteTimeGetCurrent()
        var x = 0;
        for _ in 0..<testSize {
            x = testing2(x)
        }
        let time2 = CFAbsoluteTimeGetCurrent() - time
        print("Optimised: \(x) in \(time2) seconds")
        optimisedTestTime = time2
    }
}

OptimisedTest().test()

print((testTime / optimisedTestTime) - 1)

Unless you built with whole module optimization, we can't devirtualize testing2 because Test may have subclasses in other files. Making Test private or final, or enabling -Owholemodule, should be sufficient to enable that.