http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56294
--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-01 10:27:50 UTC --- A guess is that you end up creating SSA names during code transform in different order - which can result from walking a hashtable to do things (which might be in different order when it doesn't have the same number of entries). Note that if you process debug stmts _at all_ (thus end up creating new SSA names because of them) then this will break as well.
