Rust does work with LLVM releases. In the past it didn't because of various bugs in LLVM, but all blocking bug fixes landed, where "blocking" is defined as thos

Rust does work with LLVM releases. In the past it didn't because of various bugs in LLVM, but all blocking bug fixes landed, where "blocking" is defined as those preventing compiler bootstrap. Currently, Rust CI checks for every commit that it bootstraps with LLVM 3.7 branch. Rust maintains the fork because in the foreseeable future, there will be non-blocking bug fixes and Rust will not follow LLVM trunk to get them.