[Bug rtl-optimization/56181] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1581 with -ftracer

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56181

--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> 2013-02-06 16:00:02 UTC ---
(In reply to comment #11)
> Created attachment 29371 [details]
> final patch
> 
> This is what I am considering seriously.  It adds the dumping (but we don't
> have info on the BB index of removed loops - bah), and also moves loop removal
> to fix_loop_structure again.
> 
> It doesn't fix IRAs (pre-existing) ugliness.
> 
> The previous patch passed bootstrap, I'm giving this one full testing
> (it co-incidentially fixes the bug as well).

Fixes it as part of fix_loop_structure as called from VRPs TODO_cleanup_cfg.
This is where a former irreducible region (loop with multiple entries) is
turned into a regular loop.  It's a loop having both loop 2 and loop 3 as
siblings and having loop 1 as parent.