I know of no tool that does that. When people talk about code coverage, they are generally talking about what code is tested. Personally, I feel that the term is used mostly for people to feel good and is something of an exercise in self deception.

What you are wanting is a reasonable thing, I just don't think it exists. Profilers might come close, though I don't think I have seen one that does quite that. Profilers are looking at how a function performs, which will be due to the code executed in the function, but that doesn't say which part of the function was executed and which was not. Every If statement would take only one path in any one execution, and the profiler only looks at the performance of whichever path was taken.

I, too, would find a use in a tool that could say, "this branch of code has never been followed." If you knew that, then you would also know where bugs might lie, or where there might be some code that could be removed.