Maybe some embedded systems distro have tried but as far as I know not any major distro. That would probably uncover quite a lot of bugs and require adaptations since lot of code assume Intel and compatible are either x86 or x86_64 and address memory accordingly.
There are some people trying to port Archlinux to x32 but I really don't know the status.
There are some people trying to port Archlinux to x32 but I really don't know the status.
[edit] An one year old LWN article : http://lwn.net/Articles/548838/