Upon further inspection they disabled pre compiled bridging by default before release https://github.com/apple/swift/commit/5b9166ba8098a23e0601aac96ede363dea2

Upon further inspection they disabled pre compiled bridging by default before release https://github.com/apple/swift/commit/5b9166ba8098a23e0601aac96ede363dea2484ae https://github.com/apple/swift/commit/5b9166ba8098a23e0601aa... After turning it on compilation speed seemed to improve immensely