How much it gets there, depends on squizzing juice out of LLVM backend for Swift code.
Chris Lattner, the creator of both LLVM and Swift, has referred to Swift as “syntactic sugar for LLVM.” They are deeply tied together.
The amount of Swift code in Apple's operating systems has increased every year.
https://blog.timac.org/2023/1019-state-of-swift-and-swiftui-...
Lattner gave an interview looking at the advantages of reference counting over the sort of garbage collection used in languages like Java, C#, and Go while still avoiding error-prone manual memory management.
> ARC has clear advantages in terms of allowing Swift to scale down to systems that can’t tolerate having a garbage collector, for example, if you want to write firmware in Swift. I think that it does provide a better programming model where programmers think just a little bit about memory.
Apple has also optimized their custom ARM core to further reduce the cost.
> retaining and releasing an NSObject takes ~30 nanoseconds on current gen Intel, and ~6.5 nanoseconds on an M1
https://blog.metaobject.com/2020/11/m1-memory-and-performanc...
That said, Swift is working toward adding a future opt-in Rust inspired approache to memory management for those who need it.
https://forums.swift.org/t/manifesto-ownership/5212
https://forums.swift.org/t/a-roadmap-for-improving-swift-per...
Rust and Swift are the two most widely used.
Interestingly, Swift had interoperating with C as an explicit design goal, while Rust had data race safety as a design goal.
Now we have data race safety added in the latest version of Swift, and Rust looking to improve interoperability with C.