Loop optimiser upgrade (Was RFC: BB duplication code)

[Michael Hayes]

Jan Hubicka writes:
 > What do you think about restructuring it to kind of "loop library"
 > as I've mentioned previously?
 > 
 > As we already have code to discover loops, I would love to see everything
 > designed in similar way - ie function to create preheaders/landing pads,
 > function to discover invariants, function to discover BIVs and implement each
 > optimization as separate pass.

Yes, I agree.  Each of these modules should be decoupled as much as
possible to simplify the maintenance.

Maybe we should try the unthinkable and have a go at designing the
interfaces first ;-)

Michael.