[Bug lto/88140] [9 Regression] ICE: verify_gimple failed since r266325

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88140

--- Comment #3 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 22 Nov 2018, hubicka at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88140
> 
> --- Comment #2 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
> I am testing:
> Index: tree-cfg.c
> ===================================================================
> --- tree-cfg.c  (revision 266382)
> +++ tree-cfg.c  (working copy)
> @@ -3196,8 +3196,8 @@ verify_types_in_gimple_reference (tree e
>               error ("invalid COMPONENT_REF offset operator");
>               return true;
>             }
> -         if (!useless_type_conversion_p (TREE_TYPE (expr),
> -                                         TREE_TYPE (TREE_OPERAND (expr, 1))))
> +         if (!useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (expr, 1)),
> +                                         TREE_TYPE (expr)))
>             {
>               error ("type mismatch in component reference");
>               debug_generic_stmt (TREE_TYPE (expr));

That's broken.  I'd rather adjust useless_type_conversion_p.  We
have here  incomplete-X *[] vs. complete-X *[], right?  But
how does

174               && (!TYPE_SIZE (inner_type)
175                   || TREE_CODE (TYPE_SIZE (inner_type)) != INTEGER_CST
176                   || !tree_int_cst_equal (TYPE_SIZE (outer_type),
177                                           TYPE_SIZE (inner_type))))

anything differ here?  The sizes of the pointers are equal!?

Ah,

(gdb) p inner_type->type_common.size
$1 = <tree 0x0>
(gdb) p outer_type->type_common.size
$2 = <integer_cst 0x7ffff687ad08>

why's that?!  That's probably the issue.  For ARRAY_TYPEs you
have to avoid doing TYPE_SIZE() = NULL; since you only want to
make pointed-to types of elements incomplete.