I found a LLVM IR incompatibility once, and it was already fixed. It seems some checks run for compatibility with released versions. I'm not sure whether they'r

I found a LLVM IR incompatibility once, and it was already fixed. It seems some checks run for compatibility with released versions. I'm not sure whether they're entirely automatic and systematic, but they do happen. However, the way I found it is that it affected the random version of LLVM trunk stable rustc was using at the time... That's one of the reasons why stable rust should stay away from LLVM trunk.