D55348 replaces @objc_msgSend with @llvm.objc.msgSend in tests together with many other objc intrinsics. However, this is not a recognized intrinsic (https://llvm.org/docs/LangRef.html#objective-c-arc-runtime-intrinsics) and does not receive special treatment by LLVM. It's likely that uses of this function were renamed by accident.
This came up in D106013, because the address of @llvm.objs.msgSend is taken, something which is normally not legal for intrinsics.