Julia is particularly sensitive to LLVM compile times. LLVM 11 did improve those over LLVM 10 (which had noticeable regressions versus LLVM 9). As an example see https://github.com/JuliaLang/julia/issues/37915#issuecomment...

Julia devs are posting things like:

    julia-master with llvm10:
    % julia-master --project=. --startup-file=no -e '@time using Plots'
      4.028043 seconds (6.51 M allocations: 470.491 MiB, 4.07% gc time, 16.62% compilation time)
    llvm11:
    % julia-master --project=. --startup-file=no -e '@time using Plots'
      3.392166 seconds (5.97 M allocations: 431.075 MiB, 3.46% gc time, 17.22% compilation time)

So it looks promising that the startup + compilation time is improved.

Our internal mono-repo with about 11000 C++ compilation units took about the same time with clang-11 compared to clang-10. I used the Ubuntu 20.04 packages from apt.llvm.org for testing.

We fixed a method taking 13% of Linux kernel compiles in llvm-11.

I don't have a link on me, but I recall that Rust reported some improved compilation time from upgrading to LLVM 11 (which is the default for 1.47, released last week).