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 DA4F8C2D0DB for ; Wed, 29 Jan 2020 13:24:16 +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 347412070E for ; Wed, 29 Jan 2020 13:24:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 347412070E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48742N3bqlzDqMl for ; Thu, 30 Jan 2020 00:24:12 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Unknown mechanism found: ip:192.40.192.88/32) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4873y76PJCzDqLh for ; Thu, 30 Jan 2020 00:20:27 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 00TDKK3S010139; Wed, 29 Jan 2020 07:20:20 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 00TDKJZP010137; Wed, 29 Jan 2020 07:20:19 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Wed, 29 Jan 2020 07:20:19 -0600 From: Segher Boessenkool To: Nicholas Piggin Subject: Re: powerpc Linux scv support and scv system call ABI proposal Message-ID: <20200129132019.GL22482@gate.crashing.org> References: <1580207907.c96c1lh9t0.astroid@bobo.none> <87tv4fd8wp.fsf@oldenburg2.str.redhat.com> <1580218232.2tezmthp1x.astroid@bobo.none> <1580273424.ea818exa2c.astroid@bobo.none> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1580273424.ea818exa2c.astroid@bobo.none> User-Agent: Mutt/1.4.2.3i 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: linuxppc-dev@lists.ozlabs.org, Adhemerval Zanella Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Jan 29, 2020 at 02:58:44PM +1000, Nicholas Piggin wrote: > Adhemerval Zanella's on January 29, 2020 3:26 am: > > __asm__ __volatile__ \ > > ("sc\n\t" \ > > "bns+ 1f\n\t" \ > > "neg %1, %1\n\t" \ > > "1:\n\t" \ > True, but the taken branch would be a 1 cycle bubble in fetch. Could > avoid that by branching out of line then back for the error case. But > mfocrf is fine (only sources one register), that's what should be used > here I think. neg %9,%1 ; isel %1,%9,%1,so > That probably makes the performance argument for avoiding CR[SO] for > error return indication less significant. Commonality with other > architectures is probably the bigger reason for it. Yes, and to have the syscall calling convention closer to the normal function calling convention would be good, too. Segher