I cannot see anything wrong with your function. But if you single-step it through a Simulator, you can see where it may go wrong.

You are writing a comparison function that you will find useful in many other programs.

As a general rule, it well worth carefully documenting the calling procedure, function behaviour, return value, and any registers used/trashed.

When you have it working properly, save it as a separate library file that you can .include in another project.

David.