Recursive inner functions a thousand times slower?

General Usage Performance
3

I was playing around with this and can someone explain me this: Just by removing the type annotation I get 4x faster execution. In the meantime the @code_warntype code remains the same:

function f2(y)
    loop(x) = x > 0 ? 1 + loop(x-1) : 0
    loop(y)
end

In my machine f(100) runs in 14μs and f2(100) in 3μs.

julia> @btime f2(100)
3.066 μs (2 allocations: 32 bytes)

What surprises me is that even @code_llvm code looks the same. Is there any way to understand what is going on here ?

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