Differentiable の方でも KeyPath の高速化に取り組んでいるらしく (Forums より) て，ランタイム側の変更だけでも割と速くなるみたいですね． https://github.com/apple/swift/pull/60758 (edited)

KeyPath performance improvement: Omit projection across trivially-t...

The main assumption associated with this performance improvement is that any contiguous region of (KeyPathComponentKind) structs is trivially-typed, and as such, can be traversed via simple pointer...

4:52 PM

64 倍高速化されたテストケースを覗いてみたら今日のスライドの序盤で 34 倍遅い例として出てたシンプルな使い方と似てました． https://github.com/apple/swift/blob/730bf2403582f35e85a13045416f7a761d0552d2/benchmark/single-source/KeyPathPerformanceTests.swift#L1548 (edited)

swift/KeyPathPerformanceTests.swift at 730bf2403582f35e85a13045416f...

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