[Bug tree-optimization/57275] [4.9 Regression] Error in data dependence analysis during gather vectorization

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57275

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
t.c:11: note: versioning for alias not supported for: can't determine
dependence between b[i_12] and b[_4]

this should cause vectorization to fail ... oops:

Index: tree-vect-data-refs.c
===================================================================
--- tree-vect-data-refs.c       (revision 198867)
+++ tree-vect-data-refs.c       (working copy)
@@ -269,7 +269,7 @@ vect_analyze_data_ref_dependence (struct
              dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                                 DR_REF (drb));
            }
-         return false;
+         return true;
        }

       if (dump_enabled_p ())

should fix it.