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Mon, 13 Nov 2023 08:09:47 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 38ADD20043; Mon, 13 Nov 2023 08:09:47 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B3CB420040; Mon, 13 Nov 2023 08:09:45 +0000 (GMT) Received: from [9.200.50.86] (unknown [9.200.50.86]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 13 Nov 2023 08:09:45 +0000 (GMT) Message-ID: <5cd48c76-a783-4577-8035-0ab922e32855@linux.ibm.com> Date: Mon, 13 Nov 2023 16:09:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Fwd: [PATCH, expand] Call misaligned memory reference in expand_builtin_return [PR112417] Content-Language: en-US From: HAO CHEN GUI To: Andrew Pinski Cc: Richard Biener , "Kewen.Lin" , gcc-patches References: In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 3yAmdgq8wiFh-ttGcvqSTnyFTAQC7Xtp X-Proofpoint-GUID: 5GrrXT3JkVdq22W3GYjwxokK_YY-GGk7 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-12_24,2023-11-09_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 adultscore=0 bulkscore=0 phishscore=0 suspectscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311130069 X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00,BODY_8BITS,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: 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); > 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 > 收件人: HAO CHEN GUI > 抄送: gcc-patches , Kewen.Lin > > On Fri, Nov 10, 2023 at 11:10 AM HAO CHEN GUI 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 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