PING^1: [PATCH] Add TYPE_EMPTY_RECORD for C++ empty class

[H.J. Lu]

On Tue, Mar 15, 2016 at 12:32 PM, Jason Merrill <jason@redhat.com> wrote:
> On 03/15/2016 12:00 PM, H.J. Lu wrote:
>>
>> On Tue, Mar 15, 2016 at 8:35 AM, Jason Merrill <jason@redhat.com> wrote:
>>>
>>> I'm concerned about how this patch changes both target-independent code
>>> and
>>> target-specific code, with a passing remark that other targets might need
>>> to
>>> make similar changes.  I'm also concerned about the effect of this on
>>> other
>>> languages that might not want the same change.  So, here's an alternative
>>> patch that implements the change in the front end (and includes your
>>> testcases, thanks!).
>>>
>>> Thoughts?
>>
>>
>> On x86-64, I got
>>
>>
>> /export/gnu/import/git/sources/gcc/libstdc++-v3/src/c++11/cxx11-shim_facets.cc:273:23:
>> error: empty class ‘std::__facet_shims::other_abi {aka
>> std::integral_constant<bool, true>}’ parameter passing ABI changes in
>> -fabi-version=10 (GCC 6) [-Werror=abi]
>>      __collate_transform(other_abi{}, _M_get(), st, lo, hi);
>
>
> Right, need to remove the -Werror=abi bit from the patch until Jonathan
> updates libstdc++.
>
> Jason
>

I got

FAIL: g++.dg/abi/pr60336-1.C   scan-assembler jmp[\t ]+[^$]*?_Z3xxx9true_type
FAIL: g++.dg/abi/pr60336-5.C   scan-assembler jmp[\t ]+[^$]*?_Z3xxx9true_type
FAIL: g++.dg/abi/pr60336-6.C   scan-assembler jmp[\t ]+[^$]*?_Z3xxx9true_type
FAIL: g++.dg/abi/pr60336-7.C   scan-assembler jmp[\t ]+[^$]*?_Z3xxx9true_type
FAIL: g++.dg/abi/pr60336-9.C   scan-assembler jmp[\t ]+[^$]*?_Z3xxx9true_type
FAIL: g++.dg/abi/pr68355.C   scan-assembler jmp[\t
]+[^$]*?_Z3xxx17integral_constantIbLb1EE

They are expected since get_ref_base_and_extent needs to be
changed to set bitsize to 0 for empty types so that when
ref_maybe_used_by_call_p_1 calls get_ref_base_and_extent to
get 0 as the maximum size on empty type.  Otherwise, find_tail_calls
won't perform tail call optimization for functions with empty type
parameters.

-- 
H.J.