On Mon, Nov 23, 2015 at 12:53 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Nov 23, 2015 at 1:57 AM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>> On Sat, Nov 21, 2015 at 12:46 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Fri, Nov 20, 2015 at 2:17 PM, Jason Merrill <jason@redhat.com> wrote:
>>>> On 11/20/2015 01:52 PM, H.J. Lu wrote:
>>>>>
>>>>> On Tue, Nov 17, 2015 at 4:22 AM, Richard Biener
>>>>> <richard.guenther@gmail.com> wrote:
>>>>>>
>>>>>> On Tue, Nov 17, 2015 at 12:01 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>>>>
>>>>>>> Empty record should be returned and passed the same way in C and C++.
>>>>>>> This patch adds LANG_HOOKS_EMPTY_RECORD_P for C++ empty class, which
>>>>>>> defaults to return false.  For C++, LANG_HOOKS_EMPTY_RECORD_P is defined
>>>>>>> to is_really_empty_class, which returns true for C++ empty classes.  For
>>>>>>> LTO, we stream out a bit to indicate if a record is empty and we store
>>>>>>> it in TYPE_LANG_FLAG_0 when streaming in.  get_ref_base_and_extent is
>>>>>>> changed to set bitsize to 0 for empty records.  Middle-end and x86
>>>>>>> backend are updated to ignore empty records for parameter passing and
>>>>>>> function value return.  Other targets may need similar changes.
>>>>>>
>>>>>>
>>>>>> Please avoid a new langhook for this and instead claim a bit in
>>>>>> tree_type_common
>>>>>> like for example restrict_flag (double-check it is unused for
>>>>>> non-pointers).
>>>>>
>>>>>
>>>>> There is no bit in tree_type_common I can overload.  restrict_flag is
>>>>> checked for non-pointers to issue an error when it is used on
>>>>> non-pointers:
>>>>>
>>>>>
>>>>> /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/template/qualttp20.C:19:38:
>>>>> error: ‘__restrict__’ qualifiers cannot be applied to ‘AS::L’
>>>>>     typedef typename T::L __restrict__ r;// { dg-error "'__restrict__'
>>>>> qualifiers cannot" "" }
>>>>
>>>>
>>>> The C++ front end only needs to check TYPE_RESTRICT for this purpose on
>>>> front-end-specific type codes like TEMPLATE_TYPE_PARM; cp_type_quals could
>>>> handle that specifically if you change TYPE_RESTRICT to only apply to
>>>> pointers.
>>>>
>>>
>>> restrict_flag is also checked in this case:
>>>
>>> [hjl@gnu-6 gcc]$ cat x.i
>>> struct dummy { };
>>>
>>> struct dummy
>>> foo (struct dummy __restrict__ i)
>>> {
>>>   return i;
>>> }
>>> [hjl@gnu-6 gcc]$ gcc -S x.i -Wall
>>> x.i:4:13: error: invalid use of ‘restrict’
>>>  foo (struct dummy __restrict__ i)
>>>              ^
>>> x.i:4:13: error: invalid use of ‘restrict’
>>> [hjl@gnu-6 gcc]$
>>>
>>> restrict_flag can't also be used to indicate `i' is an empty record.
>>
>> I'm sure this error can be done during parsing w/o relying on TYPE_RESTRICT.
>>
>> But well, use any other free bit (but do not enlarge
>> tree_type_common).  Eventually
>> you can free up a bit by putting sth into type_lang_specific currently
>> using bits
>> in tree_type_common.
>
> There are no bits in tree_type_common I can move.  Instead,
> this patch overloads side_effects_flag in tree_base.  Tested on
> Linux/x86-64.  OK for trunk?
>
> Thanks.
>
> --
> H.J.



-- 
H.J.