Looks like there's consensus to accept it as an "experimental" backend. I think that means the code is in tree, but other people changing LLVM aren't obligated to keep it working.

It may be accepted as a full backend in the future, but that discussion is deferred since people are happy with it being experimental for now.

GCC has done it for years. For LLVM mainline, often for small and simple architectures, the people contributing to mainline is much more valuable than the cost of having to make mechanical API changes in that backend when codegen api's are changed.

(Once you have > ~5 backends, which LLVM does the cost of doing the latter just doesn't really change much).

If you want to build a real community, turning away contributions likely to lead to an overall net positive for the community tends not to be a good approach :)

(I await the arguments about corporations having no care about communities or whatever else)

It's not exactly unprecedented. GCC supports mmix, which hardware doesn't even exist for. (An educational platform from TAOCP.)

https://gcc.gnu.org/backends.html

Ordinarily I'd agree with you. Except the tradeoff of having Google's other contributions to the main branch is probably worth it for a little bit of code that isn't harming anyone else.

It's perhaps not fair, but just a reality that a company like Google has a lot to offer so they can sometimes get special treatment.