It's worth remembering Swift's implementation of ARC is still far from optimal. Swift 5.3's optimizer significantly reduces the number of ARC calls in optimized code; we've seen up to 2x improvements in hot parts of SwiftUI and Combine without code changes. There will continue to be ARC optimizer improvements as we propagate OSSA SIL through the optimizer pipeline as well. (However, the main benefit of ARC over other forms of GC will always be lower-overhead interop with non-GC-managed resources, such as the large volumes of C, C++, and growing amount of value-oriented Swift code that implements the lower level parts of the OS, rather than the performance of the heap management itself.)
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