false alarm involving a private constant

[regehr]

have we seen this one before? I don't recognize it.

https://alive2.llvm.org/ce/z/YQDPnt

@x = private constant i32 1

define i32 @f(ptr %data) {
entry:
  ret i32 0

dead:    
  call void null(ptr @x)
  unreachable
}