The headline is clang vs. other open-source compilers, not sure if VC++ qualifies.

open64 had link-time optimization in the early 2000s. (although they called it IPA for interprocedural analysis).

It was first released in VC++ in 2002.

I don’t recall if HP actually shipped it, but I know they had a tech report or research paper around 1994 that did LTO.

I have a vague recollection that DEC may have shipped it in the 90s as well.