Re: Improve unrolled size estimates

[Jan Hubicka <hubicka at ucw dot cz>]

> > I guess it ought to handle unknown constant too and claim that result is
> > unknown constant, right? (it doesn't)
> 
> Yes, that's a missed optimization.  We'd need to invent some tree
> to return for 'unknown constant' though.

OK, so I guess the overal plan would be

1) fix CCP so it can estimate that load from initialized constant array
or string will be unknown constant if all indices are unknown constants
2) reorganize SSA propagator to work on specified blocks
3) add support for partially populating CCP lattices by "varying" for
everything that is not IV variable and not defined inside the selected
blocks
4) add support for CCP to do only propagation and return list of
statements that are constant now
5) reorganize the cost function to use result of it instead of my
constant_after_peeling predicate

I am affraid that I don't have time right now to do all that, there are
still too many other things on my TODO list.

I've dropped the patch into pretty-ipa.  There are several improvemnts:
  SPECINT  EON 2130->2465 (base only).  GEOM is up 1433->1454
  EON has loop zeroing small vector in the internal loop.  I guess it
  now gets fully unrolled.  Size seems same.
  SPECFP base Wupwise 1485->1491, swim 1529->1540, applu 1250->1275,
  equake 1680->1775, facerec 1991->2030, 
  (equake is important)
  SPECFP peak wupwise 1395->1417, applu 1326->1355, mesa 1472->1500
  art 2219->2248, 

There is also code size regression on botan
http://gcc.opensuse.org/c++bench-frescobaldi-ipa-64/botan/
and raytracer
http://gcc.opensuse.org/c++bench-frescobaldi-ipa-64/raytracer/

So I guess it is worthwhile to play with it.  I would be however happy
if someone beats me ;)))

Honza
> 
> Richard.