Rust is experimenting with a codegen tool called cranelift which powers wasmtime. The plan is to use it for debug builds. There is also a backend implementation in the works using gcc jit and a dotnet backend as well
Zig is actually trying to get rid of LLVM for default builds, though they intend to keep it as one of the "backends" for the forseeable future.
The problem is that LLVM is very slow (as it applies lots of optimisations) and heavy, and that makes a compiler slow even in debug mode.
D has 3 backends, LLVM is used by the LDC compiler. Then there's DMD which is the official compiler (and frontend for all three), and GDC which uses GCC backend. D code typically compiles quite a bit faster on DMD, but the code is more highly optimised with LLVM or GCC, of course. It's a great tradeoff specially since all compilers use the DMD frontend so it's almost guaranteeed that there's no differences in behaviour between them.
