machine register info

hi
    I find machine register info carrying the lists of def use for
each register - PhysRegUseDefLists[RegNo];. I dont see a lot of places
using this. For instance, if this list is accurate, can this be used
for def use relationships at different points?

thanks
shrey

Think found it ..its just meant for fast updating registers before RA.
Orders missing to use it for any def use purposes ...

shrey