Most of mainstream compilers are the output of academics work.
A lot of modern compilers don't seem to be directly done by academics though. If you know of such modern examples I'd be happy to be proven wrong.
It is full of PhD paper contributions.
For example, research students doing internships at Embecosm (https://embecosm.com), as many others, plenty of material from LLVM Developers Meeting sessions.
Obviously a lot of what passes for "AI" these days is researched and created by academics.
Thanks.