[Bug middle-end/50251] [4.7 Regression] Revision 178353 caused many test failures

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50251

--- Comment #13 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-09-02 09:42:13 UTC ---
(In reply to comment #6)
> fold_builtin_alloca_for_var should record stack alignment
> change due to
> 
> +  /* Declare array.  */
> +  elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
> +  n_elem = size * 8 / BITS_PER_UNIT;
> +  align = MIN (size * 8, BIGGEST_ALIGNMENT);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +  array_type = build_array_type_nelts (elem_type, n_elem);
> +  var = create_tmp_var (array_type, NULL);
> +  DECL_ALIGN (var) = align;
> +

If the stack alignment code cannot handle decls with any DECL_ALIGN
it is broken.  We for sure do not need to do anything here nor
in the vectorizer, which does

      if (vect_can_force_dr_alignment_p (decl, alignment))
        {
          DECL_ALIGN (decl) = TYPE_ALIGN (vectype);
          DECL_USER_ALIGN (decl) = 1;