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Re: Loop optimizer issues


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.

Considering value range profiling code, I think all places where it
could conflict with Nathan's changes are isolated in instrumentation
(already merged in) and profile reading (waiting for review), so this
should not be a problem.  Of course it introduces a new optimizations
and does not fix any regressions, so it does not quite fit stage 2, but
given that it is already partially merged in, I would prefer finishing
it now.

Zdenek


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