[llvm-dev] How to understand "tail" call?

[Peng Yu via llvm-dev]

> In the example you gave, no tail call optimization can occur despite
> the calls being marked as candidates because main has to materialize
> the "return 0" code after both calls to printf have happened.

Since the tail call optimization can not be trigger any way, why the
generated IR still has the keyword "tail"? Isn't that unnecessary?

-- 
Regards,
Peng