I'm a little confused about how the "pointerness" of pointers is getting lost in LLVM. The mill can't be the only architecture that encodes extra data in the hi

I'm a little confused about how the "pointerness" of pointers is getting lost in LLVM. The mill can't be the only architecture that encodes extra data in the high bits of pointers right? The 64 bit objective-C runtime and Xbox 360 come to mind as systems where this is done. Clearly LLVM can generate good code 64 bit Objective-C... Am I missing something?