Alternative backend

[lu-zero]

Libfirm is a sort of leaner and smaller llvm, written in C and with almost no dependencies.

Might be good to implement another backend to ensure genericity.

[thestinger]

I'm not sure that this is in the scope of the official Rust project. If someone actually did the work of writing this, making the backend pluggable would make sense.

[emberian]

firm only supports x86 and SPARC, with a more limited set of optimizations. Would be fairly interesting, though, to have trans be pluggable. Not going to be easy to use a different backend, we lean on LLVM quite heavily.

[thestinger]

I can't see this happening as part of the official compiler. I don't think the extra maintenance involved would be acceptable, and it would bring the usual problem of forcing the limitations of the lowest common denominator on everyone. It belongs in a third party repository, and specific changes making it easier to maintain could possibly be dealt with here.