I believe you're correct about Open64, but it was an interesting examples of a compiler when I was researching them last, particularly its usage of WHIRL [1]. It's a similar approach as used by GCC and LLVM with their front, middle and back-end approach, although I can't quite remember if it pioneered that approach or not.

[1] https://www.mcs.anl.gov/OpenAD/open64A.pdf