Very little is done with these values in the fast path. The application in question is basically a smart proxy that performs a very minimal amount of formatting. Most of the code in the fast path is pretty linear so I was curious if there were any good way to keep this particular case conditional free.

But, you are right that it probably doesn't matter. The minimal benchmarking I did convinced us that there wouldn't be much of a cost. The code that actually ended up being committed to our project has the branch.