When -mavx was added BIGGEST_ALIGNMENT was changed to depend on it. This changes the behavior of __attribute__((aligned)), which is used to define struct _Unwind_Exception, and which changes the ABI of anything that uses it.
-- Summary: [4.4 Regression] __alignof__ (_Unwind_Exception) depends on -mavx Product: gcc Version: 4.4.0 Status: UNCONFIRMED Keywords: ABI Severity: critical Priority: P3 Component: target AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: schwab at suse dot de GCC target triplet: i?86-*-* OtherBugsDependingO 38732 nThis: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38737