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=-2.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 55DA9C004C9 for ; Tue, 7 May 2019 15:13:17 +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 0F04C2087F for ; Tue, 7 May 2019 15:13:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0F04C2087F 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 44z35R1Wq7zDqKZ for ; Wed, 8 May 2019 01:13:15 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=permerror (mailfrom) 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 44z32Y5j7tzDqLR for ; Wed, 8 May 2019 01:10:45 +1000 (AEST) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x47FAVVb020331; Tue, 7 May 2019 10:10:31 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id x47FAUGu020324; Tue, 7 May 2019 10:10:30 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 7 May 2019 10:10:30 -0500 From: Segher Boessenkool To: Christophe Leroy Subject: Re: [PATCH] powerpc: slightly improve cache helpers Message-ID: <20190507151030.GF8599@gate.crashing.org> References: <0b460a85319fb89dab2c5d1200ac69a3e1b7c1ef.1557235807.git.christophe.leroy@c-s.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0b460a85319fb89dab2c5d1200ac69a3e1b7c1ef.1557235807.git.christophe.leroy@c-s.fr> 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, Paul Mackerras , linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Christophe, On Tue, May 07, 2019 at 01:31:39PM +0000, Christophe Leroy wrote: > Cache instructions (dcbz, dcbi, dcbf and dcbst) take two registers > that are summed to obtain the target address. Using '%y0' argument > gives GCC the opportunity to use both registers instead of only one > with the second being forced to 0. That's not quite right. Sorry if I didn't explain it properly. "m" allows all memory. But this instruction only allows reg,reg and 0,reg addressing. For that you need to use constraint "Z". The output modifier "%y0" just makes [reg] (i.e. simple indirect addressing) print as "0,reg" instead of "0(reg)" as it would by default (for just "%0"). Segher