Loop optimizer issues

[Jan Hubicka]

> Hello,
> 
> > >  - Zdenek's value range profiling code.  This one is half way in the
> > >    mainline.  I really hoped to see this merged in 3.4 but I am not
> > >    quite sure this will happen.
> > >    This is major problem in merging mainline as Nathanel's work on gcov
> > >    did cause gread amount of conflicts..
> > [...]
> > >  - Josef's variable tracking and Daniel's location lists.  I believe
> > >    there is useable version sent for review for some time but it has
> > >    problem with losing track when value is copied to temporary location
> > >    that is later killed.  This is relatively minnor problem in the
> > >    algorithm as the interfaces are major problem right now here.
> > > 
> > >    I believe we have to solve this in order to get nice debugging out of
> > >    de-SSA once we drop limitations on de-SSAizing.  It is also solving
> > >    problems with -frename-registers as well as with webizer rendering
> > >    variable values random in debugger.
> > 
> > I'm not sure what to do about these.  Clearly the location list
> > support is highly desirable, but I thought you said when I pinged
> > you last is that it didn't work reliably.
> 
> there are some problems with it, I think Josef is working on them now.
> Also some bug in it caused libstdc++ not to compile, so I disabled it
> for now, but it should be easy to fix.

This is the "improved dataflow" version present in rtlopt branch that is
different from the first version sent for mainline inclusion.

Honza