Source code for LLVM toolchain?

I know that the source code for the GCC toolchain is made available. Is the source code for the LLVM toolchain available as well? I know LLVM is not a copy left license, but you could still provide the source code if you so wish. Do you have any intention of this?

If yes, do you intend to upstream your backends? That would be pretty cool!

I am speciffically interested about the RL78 backends, if my understanding is correct, then a backend of RL78 would enable me to compile Rust for RL78. ( not sure how that would look as the RL78 is quite small, smaller than Rust targets, but it’s o curiosity of mine)