I obtained slightly different results on NestedBareInit and NestedExplicitInit

[saeed-rz]

How did I test it:

• I used swiftc -typecheck {file} command.
• I removed import Foundation ( it was not necessary)
• I copied base to my test file, ( to avoid any other effects on compile time)
  Here is NestedBareInit after changes:

struct Base {
    let nested1: Nested1
    let nested2: Nested2
}

struct Nested1 {
    let grand1: GrandChild
    let grand2: GrandChild
}

struct Nested2 {
    let grand: GrandChild
}

struct GrandChild { }

let a0: Base = .init(nested1: .init(grand1: .init(), grand2: .init()), nested2: .init(grand: .init()))
....
let a999: Base = .init(nested1: .init(grand1: .init(), grand2: .init()), nested2: .init(grand: .init()))

NestedExplicitInit.swift:

struct Base {
    let nested1: Nested1
    let nested2: Nested2
}

struct Nested1 {
    let grand1: GrandChild
    let grand2: GrandChild
}

struct Nested2 {
    let grand: GrandChild
}

struct GrandChild { }

let b0 = Base(nested1: Nested1(grand1: GrandChild(), grand2: GrandChild()), nested2: Nested2(grand: GrandChild()))
...
let b999 = Base(nested1: Nested1(grand1: GrandChild(), grand2: GrandChild()), nested2: Nested2(grand: GrandChild()))

Command to test:

hyperfine 'swiftc -typecheck {NestedBareInit/NestedExplicitInit}.swift'

Results:
NestedBareInit:

Time (mean ± σ):     534.0 ms ±  15.6 ms    [User: 483.7 ms, System: 37.7 ms]
  Range (min … max):   518.4 ms … 565.7 ms    10 runs

NestedExplicitInit:

Time (mean ± σ):      1.594 s ±  0.023 s    [User: 1.550 s, System: 0.029 s]
  Range (min … max):    1.568 s …  1.644 s    10 runs

[LucasVanDongen]

What kind of machine/specs did you use?

I'm a bit surprised that you get significantly less ms on NestedBareInit, but NestedExplicitInit takes the double, while all optimizations have been applied on both tests

[saeed-rz]

I'm using M1 Max 64 GB. Mac os Sonoma 14.1.1 and Xcode Version 15.1.