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=-5.3 required=3.0 tests=BAYES_00, 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 C14E9C432BE for ; Thu, 26 Aug 2021 14:19:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FFCF60E90 for ; Thu, 26 Aug 2021 14:19:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242879AbhHZOUX (ORCPT ); Thu, 26 Aug 2021 10:20:23 -0400 Received: from gate.crashing.org ([63.228.1.57]:60012 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229832AbhHZOUR (ORCPT ); Thu, 26 Aug 2021 10:20:17 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 17QECso4020353; Thu, 26 Aug 2021 09:12:54 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 17QECseB020350; Thu, 26 Aug 2021 09:12:54 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Thu, 26 Aug 2021 09:12:54 -0500 From: Segher Boessenkool To: Michael Ellerman Cc: Nathan Chancellor , Christophe Leroy , llvm@lists.linux.dev, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Paul Mackerras , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v2 2/2] powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto Message-ID: <20210826141254.GB1583@gate.crashing.org> References: <389962b1b702e3c78d169e59bcfac56282889173.1618331882.git.christophe.leroy@csgroup.eu> <87h7fcc2m4.fsf@mpe.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h7fcc2m4.fsf@mpe.ellerman.id.au> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 26, 2021 at 01:21:39PM +1000, Michael Ellerman wrote: > So there seems to be some misunderstanding with clang, it doesn't like > us passing an expression to the inline asm. > > AFAIK it is legal to pass expressions as inputs to inline asm, ie. it > doesn't have to just be a variable name. It certainly is. That is the whole point of inline asm! This way, all of the C code "around" the asm can be optimised. > This patch seems to fix it. Not sure if that's just papering over it though. It is, and it makes less optimised code (also on GCC), as Christophe points out. Segher