There was a recent effort by Google to speed up SipHash, it's called HighwayHash: https://github.com/google/highwayhash - it includes a compatible, optimized SipHash implementation (1.5x speedup), a variation on that that is not compatible but similar, SipTreeHash (3x speedup on top of optimized implementation) and a new algorithm, HighwayHash, that yields another factor of 2-3. I haven't yet used it myself but it looks interesting and might be relevant to Rust?

Edited to add that Google's implementation targets Haswell and later (AVX-2), I don't know about the performance of an implementation that targets older CPUs which would of course be very relevant for Rust