On Mon, Nov 13, 2023 at 9:09 AM HAO CHEN GUI <guih...@linux.ibm.com> wrote: > > Sorry, forgot to cc gcc-patches. > > 在 2023/11/13 16:05, HAO CHEN GUI 写道: > > Andrew, > > Could you kindly inform us what's the functionality of __objc_forward? > > Does it change the memory content pointed by args? Thanks a lot. > > > > Thanks > > Gui Haochen > > > > > > libobjc/sendmsg.c. > > > > void *args, *res; > > > > args = __builtin_apply_args (); > > res = __objc_forward (rcv, op, args);
maybe this should use __builtin_apply and the __builtin_return use 'args', not 'res' as the return value? > > if (res) > > __builtin_return (res); > > else > > ... > > > > -------- 转发的消息 -------- > > 主题: Re: [PATCH, expand] Call misaligned memory reference in > > expand_builtin_return [PR112417] > > 日期: Fri, 10 Nov 2023 14:39:02 +0100 > > From: Richard Biener <richard.guent...@gmail.com> > > 收件人: HAO CHEN GUI <guih...@linux.ibm.com> > > 抄送: gcc-patches <gcc-patches@gcc.gnu.org>, Kewen.Lin <li...@linux.ibm.com> > > > > On Fri, Nov 10, 2023 at 11:10 AM HAO CHEN GUI <guih...@linux.ibm.com> wrote: > >> > >> Hi Richard, > >> > >> 在 2023/11/10 17:06, Richard Biener 写道: > >>> On Fri, Nov 10, 2023 at 8:52 AM HAO CHEN GUI <guih...@linux.ibm.com> > >>> wrote: > >>>> > >>>> Hi Richard, > >>>> Thanks so much for your comments. > >>>> > >>>> 在 2023/11/9 19:41, Richard Biener 写道: > >>>>> I'm not sure if the testcase is valid though? > >>>>> > >>>>> @defbuiltin{{void} __builtin_return (void *@var{result})} > >>>>> This built-in function returns the value described by @var{result} from > >>>>> the containing function. You should specify, for @var{result}, a value > >>>>> returned by @code{__builtin_apply}. > >>>>> @enddefbuiltin > >>>>> > >>>>> I don't see __builtin_apply being used here? > >>>> > >>>> The prototype of the test case is from "__objc_block_forward" in > >>>> libobjc/sendmsg.c. > >>>> > >>>> void *args, *res; > >>>> > >>>> args = __builtin_apply_args (); > >>>> res = __objc_forward (rcv, op, args); > >>>> if (res) > >>>> __builtin_return (res); > >>>> else > >>>> ... > >>>> > >>>> The __builtin_apply_args puts the return values on stack by the > >>>> alignment. > >>>> But the forward function can do anything and return a void* pointer. > >>>> IMHO the alignment might be broken. So I just simplified it to use a > >>>> void* pointer as the input argument of "__builtin_return" and skip > >>>> "__builtin_apply_args". > >>> > >>> But doesn't __objc_forward then break the contract between > >>> __builtin_apply_args and __builtin_return? > >>> > >>> That said, __builtin_return is a very special function, it's not supposed > >>> to deal with what you are fixing. At least I think so. > >>> > >>> IMHO the bug is in __objc_block_forward. > >> > >> If so, can we document that the memory objects pointed by input argument of > >> __builtin_return have to be aligned? Then we can force the alignment in > >> __builtin_return. The customer function can do anything if gcc doesn't > >> state > >> that. > > > > I don't think they have to be aligned - they have to adhere to the ABI > > which __builtin_apply_args ensures. But others might know more details > > here. > > > >> Thanks > >> Gui Haochen > >> > >>> > >>> Richard. > >>> > >>>> > >>>> Thanks > >>>> Gui Haochen