Describe the bug
Have you ever tried to build docs for the llvm-project? It uses doxygen for this and the building takes more than 20 hours! My workstation is not the most powerful in the world, of course, so it has something to do with the issue, but I don't think that using the latest Threadripper would help much.

Has anyone ever investigated the issue?

To Reproduce
Build docs for the llvm-project.

Expected behavior
20 hours is way too long.

Version
The latest release 1.12.0 and the latest doxygen available built from the sources both work 20 hours.