As for Julia on Cray,
"Julia — The Newest Petaflop Family Language We Have Started to Love"
https://www.avenga.com/magazine/julia-programming-language
> Julia is one of the few languages that are in the so-called PetaFlop family; the other languages are C, C++ and Fortrant. It achieved 1.54 petaflops with 1.3 million threads on the Cray XC40 supercomputer.
It seems to be pure Julia.
Julia uses the LLVM compiler; I’m pretty sure that’s the only platform, aside from experiments compiling to WASM.
And Julia code is not Fortran/C/C++, not sure what you are asking.
I said "Can Julia take advantage of that?". So the "that" in my question was "vendor compilers [which] often outperform GCC and LLVM... on Cray systems especially".
It seems like the answer is, no, Julia cannot be compiled with those vendor compilers that often outperform LLVM.
But it seems that Julia nonetheless has been shown to perform well, just not specifically by using those vendor compilers that I was asking about.
It's my understanding that Julia aspires to join this group of languages if it is able to do so, which is why the Petaflops announcement was originally enticing to me, and then became somewhat less so once I learned that it was relying on MPI.