From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83A36C433DF for ; Wed, 8 Jul 2020 16:14:03 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D54FE20786 for ; Wed, 8 Jul 2020 16:14:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D54FE20786 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4B24B0471TzDqX3 for ; 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Wed, 8 Jul 2020 18:11:52 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id C89F78B803; Wed, 8 Jul 2020 18:11:54 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 7OV6tqRKoiBf; Wed, 8 Jul 2020 18:11:54 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 98D6F8B804; Wed, 8 Jul 2020 18:11:51 +0200 (CEST) Subject: Re: Failure to build librseq on ppc To: Mathieu Desnoyers References: <972420887.755.1594149430308.JavaMail.zimbra@efficios.com> <20200708005922.GW3598@gate.crashing.org> <841816533.1735.1594211583710.JavaMail.zimbra@efficios.com> <1623833219.1877.1594216801865.JavaMail.zimbra@efficios.com> <96994487-ae4a-3bfb-b0f1-34228e51bea2@csgroup.eu> <1137155888.2676.1594218740683.JavaMail.zimbra@efficios.com> From: Christophe Leroy Message-ID: Date: Wed, 8 Jul 2020 18:11:30 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1137155888.2676.1594218740683.JavaMail.zimbra@efficios.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Boqun Feng , linuxppc-dev , Michael Jeanson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 08/07/2020 à 16:32, Mathieu Desnoyers a écrit : > ----- On Jul 8, 2020, at 10:21 AM, Christophe Leroy christophe.leroy@csgroup.eu wrote: > >> Le 08/07/2020 à 16:00, Mathieu Desnoyers a écrit : >>> ----- On Jul 8, 2020, at 8:33 AM, Mathieu Desnoyers >>> mathieu.desnoyers@efficios.com wrote: >>> >>>> ----- On Jul 7, 2020, at 8:59 PM, Segher Boessenkool segher@kernel.crashing.org >>>> wrote: >>> [...] >>>>> >>>>> So perhaps you have code like >>>>> >>>>> int *p; >>>>> int x; >>>>> ... >>>>> asm ("lwz %0,%1" : "=r"(x) : "m"(*p)); >>>> >>>> We indeed have explicit "lwz" and "stw" instructions in there. >>>> >>>>> >>>>> where that last line should actually read >>>>> >>>>> asm ("lwz%X1 %0,%1" : "=r"(x) : "m"(*p)); >>>> >>>> Indeed, turning those into "lwzx" and "stwx" seems to fix the issue. >>>> >>>> There has been some level of extra CPP macro coating around those instructions >>>> to >>>> support both ppc32 and ppc64 with the same assembly. So adding %X[arg] is not >>>> trivial. >>>> Let me see what can be done here. >>> >>> I did the following changes which appear to generate valid asm. >>> See attached corresponding .S output. >>> >>> I grepped for uses of "m" asm operand in Linux powerpc code and noticed it's >>> pretty much >>> always used with e.g. "lwz%U1%X1". I could find one blog post discussing that %U >>> is about >>> update flag, and nothing about %X. Are those documented ? >> >> As far as I can see, %U is mentioned in >> https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html in the >> powerpc subpart, at the "m" constraint. > > Yep, I did notice it, but mistakenly thought it was only needed for "m<>" operand, > not "m". You are right, AFAIU on recent versions of GCC, %U has no effect without m<> Christophe > > Thanks, > > Mathieu > >> >> For the %X I don't know. >> >> Christophe >> >>> >>> Although it appears to generate valid asm, I have the feeling I'm relying on >>> undocumented >>> features here. :-/ >