[[carries_dependency]] what it means and how to implement

I was reading about [[carries_dependency]] in this SO post.

But what I could not understand is the below sentences in the accepted answer :

"In particular, if a value read with memory_order_consume is passed in to a function, then without [[carries_dependency]], then the compiler may have to issue a memory fence instruction to guarantee that the appropriate memory ordering semantics are upheld. If the parameter is annotated with [[carries_dependency]] then the compiler can assume that the function body will correctly carry the dependency, and this fence may no longer be necessary.

Similarly, if a function returns a value loaded with memory_order_consume, or derived from such a value, then without [[carries_dependency]] the compiler may be required to insert a fence instruction to guarantee that the appropriate memory ordering semantics are upheld. With the [[carries_dependency]] annotation, this fence may no longer be necessary, as the caller is now responsible for maintaining the dependency tree."

Lets take it step by step:

"if a value read with memory_order_consume is passed in to a function, then without [[carries_dependency]], then the compiler may have to issue a memory fence instruction to guarantee that the appropriate memory ordering semantics are upheld."

So for an atomic variable in release-consume memory model when atomic variable is being passed as a parameter to the function the compiler will introduce a fence hardware instruction so that it always has the latest and updated value of the atomic variable provided to the function.

Next -

"If the parameter is annotated with [[carries_dependency]] then the compiler can assume that the function body will correctly carry the dependency, and this fence may no longer be necessary."

This is confusing me - the atomic variable value is already consumed and then what dependency the function is carried?

Similarly -

"if a function returns a value loaded with memory_order_consume, or derived from such a value, then without [[carries_dependency]] the compiler may be required to insert a fence instruction to guarantee that the appropriate memory ordering semantics are upheld. With the [[carries_dependency]] annotation, this fence may no longer be necessary, as the caller is now responsible for maintaining the dependency tree."

From the example its not clear what the point it is trying to state about carrying the dependency?