.NET Core 3 (in preview, due out Sep 23) includes support for popcount as part of the BitOperations class: https://docs.microsoft.com/en-us/dotnet/api/system.numerics..... There's a recent post describing hardware intrinsics in .NET Core: https://devblogs.microsoft.com/dotnet/hardware-intrinsics-in...

There are a lot of potential use cases, but one of the early discussions was around quickly scanning for known HTTP headers. You can see that in use here: https://github.com/aspnet/AspNetCore/blob/caa910ceeba5f2b2c0...

If you really need help falling asleep, here's the discussion going back to 2015: https://github.com/dotnet/corefx/issues/2209

Disclaimers: Microsoft employee, Nazgûl