http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57955
David Edelsohn <dje at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|Uniquization of constants |[4.6/4.7/4.8/4.9 |breaks constant alignment |Regression] Uniquization of | |constants reduces alignment | |of initializers --- Comment #5 from David Edelsohn <dje at gcc dot gnu.org> --- It was an undocumented change in GCC behavior. I infer from the name that the testcase was trying to test that a block move of appropriate alignment used VMX instructions. I will see if I can construct a testcase with memcpy directly.