[Bug tree-optimization/55860] Turn segmented iteration into nested loops

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55860

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-01-03
                 CC|                            |law at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-01-03 16:17:17 UTC ---
Hmm, jump threading should notice this.  But it is confused by loop header
copying which made the header test 0 < n instead.  There is also the
complication that this threading would create a loop with multiple latches
which isn't generally desirable even though we can disambiguate those
into a loop nest.

But it doesn't seem to register any of the jump threading opportunities
in the first place (DOM, that is).  Jeff - maybe something for you to look at.