We recently switched to using the CoreClr compiler for builds in VS instead of the desktop compiler. Doing so, we regressed compile-time performance.
TFM: net5

// Learn more about F# at http://docs.microsoft.com/dotnet/fsharp

open System

// Define a function to construct a message to print
let from whom =
    sprintf "from %s" whom

[<EntryPoint>]
let main argv =
    let message = from "F#" // Call the function
    printfn "Hello world %s" message
    0 // return an integer exit code

CoreClr compiler: 1326 ms Fsc 1 calls
Desktop compiler: 586 ms Fsc 1 calls

It's over double the cost.

This is basically the startup time; I imagine the compiler doesn't actually perform worse on the CoreClr. However, this can be surprising for users as the additional 740ms build-cost per project will add up.