http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52996
--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-16 10:58:06 UTC --- Looks like a pre-existing bug to me - when we unswitch loops computing irreducible regions before / after that can lead to inconsistent results. Loop preserving leads to different loop structure at the beginning of RTL unswitching compared to the 4.7 branch.
