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=-2.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,PDS_BAD_THREAD_QP_64, SPF_HELO_NONE,SPF_PASS 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 C1791C433E0 for ; Thu, 4 Feb 2021 10:31:15 +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 3625E64DEB for ; Thu, 4 Feb 2021 10:31:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3625E64DEB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ACULAB.COM 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 4DWZb50FD4zDwnr for ; Thu, 4 Feb 2021 21:31:13 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=aculab.com (client-ip=207.82.80.151; helo=eu-smtp-delivery-151.mimecast.com; envelope-from=david.laight@aculab.com; receiver=) Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [207.82.80.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4DWZXl5tl5zDwtQ for ; Thu, 4 Feb 2021 21:29:09 +1100 (AEDT) Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-156-FUxuok8FPYibgYXVDY-O-w-1; Thu, 04 Feb 2021 10:29:02 +0000 X-MC-Unique: FUxuok8FPYibgYXVDY-O-w-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 4 Feb 2021 10:29:00 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Thu, 4 Feb 2021 10:29:00 +0000 From: David Laight To: 'Segher Boessenkool' , "Naveen N. Rao" Subject: RE: [PATCH v2 1/3] powerpc: sstep: Fix load and update emulation Thread-Topic: [PATCH v2 1/3] powerpc: sstep: Fix load and update emulation Thread-Index: AQHW+nKP6kL5mXAGDkmDhNs6SM6B+qpHysqQ Date: Thu, 4 Feb 2021 10:29:00 +0000 Message-ID: <10d7cf245bb744739de063d452065e94@AcuMS.aculab.com> References: <20210203063841.431063-1-sandipan@linux.ibm.com> <20210203094909.GD210@DESKTOP-TDPLP67.localdomain> <20210203211732.GD30983@gate.crashing.org> In-Reply-To: <20210203211732.GD30983@gate.crashing.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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: "ravi.bangoria@linux.ibm.com" , "ananth@linux.ibm.com" , "jniethe5@gmail.com" , "paulus@samba.org" , Sandipan Das , "linuxppc-dev@lists.ozlabs.org" , "dja@axtens.net" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Segher Boessenkool > Sent: 03 February 2021 21:18 ... > Power9 does: >=20 > Load with Update Instructions (RA =3D 0) > EA is placed into R0. Does that change the value of 0? Rather reminds me of some 1960s era systems that had the small integers at fixed (global) addresses. FORTRAN always passes by reference, pass 0 and the address of the global zero location was passed, the called function could change 0 to 1 for the entire computer! > Load with Update Instructions (RA =3D RT) > The storage operand addressed by EA is accessed. The displacement > field is added to the data returned by the load and placed into RT. Shame that isn't standard - could be used to optimise some code. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)