def use at O0

Hi all
I would like to have access to def-use relationships at O0 , for now after register allocation. So my question is

  1. is there any such existing information ? If not, do i need to build it from scratch by traversing all the instructions and operands ?

  2. While for now I only need it Post RA but eventually I want to use it before RA as well. Suggestions on how i can go abt that would help me reuse code/def-use data would be great !

thanks for all help !

Can some one help please ?
To give a broader context here, I feel O0 would be good starting point for a fast compiler but I would like to add some optimizations to it after register allocation.

Thoughts on the topic would be of great help to me