> It is nice that there is now a language with first-class SIMD support, comparing with something implemented with a library If the language is flexible enough

> It is nice that there is now a language with first-class SIMD support, comparing with something implemented with a library If the language is flexible enough (in particular, it has to support operator overloading), I don’t see any disadvantages to implementing that in a library. See for example https://developer.apple.com/documentation/swift/simd https://developer.apple.com/documentation/swift/simd