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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 2DB16C43331 for ; Thu, 26 Mar 2020 11:00:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED0FB2073E for ; Thu, 26 Mar 2020 11:00:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=st.com header.i=@st.com header.b="JH9clXki" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728004AbgCZLAF (ORCPT ); Thu, 26 Mar 2020 07:00:05 -0400 Received: from mx08-00178001.pphosted.com ([91.207.212.93]:47192 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727590AbgCZLAF (ORCPT ); Thu, 26 Mar 2020 07:00:05 -0400 Received: from pps.filterd (m0046661.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02QAw3le004718; Thu, 26 Mar 2020 11:59:53 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=st.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=STMicroelectronics; bh=ePaRO2xQxOSssih3ATmMumUDQxzntYCKLl5miAQMV5w=; b=JH9clXkigdRraWQGXYGOr5OIW5C0DUutbVjb3FjeIpaKChItgfANVt8ZSlPcbAJ29JQF pcXwgEF3oq3ZiT6SlQBovqwa4XPGP0NoiabrJ1AzHyhzX0GHTYH3irwUrSjfNk3+j+np MT1qeeRo276ThIrrCloKGNcKxcoD8mSyc/Q08WnSeXaDcNLF2dPbyfV++pERS0Cba980 YiUF7ir7TU7okOhmKfyC+9/kHPHg9eqRHCH3HiiCWeBH5MBY+kRZw76BxYUJOne1rqH5 W9AZOg+uxLaMXCevPQSgT805s254FyCGJhIvJkehDIav9m5nVL/6W/ykSz11n5fRACKz Dg== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com with ESMTP id 2ywappb5e0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 26 Mar 2020 11:59:53 +0100 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 84D8F100038; Thu, 26 Mar 2020 11:59:48 +0100 (CET) Received: from Webmail-eu.st.com (sfhdag3node1.st.com [10.75.127.7]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 6DC9E2A5553; Thu, 26 Mar 2020 11:59:48 +0100 (CET) Received: from lmecxl0889.tpe.st.com (10.75.127.46) by SFHDAG3NODE1.st.com (10.75.127.7) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 26 Mar 2020 11:59:38 +0100 Subject: Re: [PATCH v7 2/2] tty: add rpmsg driver To: Joe Perches , Jiri Slaby , Ohad Ben-Cohen , Bjorn Andersson , Greg Kroah-Hartman , , , Mathieu Poirier CC: Suman Anna , Fabien DESSENNE , , xiang xiao References: <20200324170407.16470-1-arnaud.pouliquen@st.com> <20200324170407.16470-3-arnaud.pouliquen@st.com> <1e4ce821-dd9b-bb04-774b-58a255834cf5@st.com> From: Arnaud POULIQUEN Message-ID: <54d9b379-ba51-b29c-db58-6e305773ee96@st.com> Date: Thu, 26 Mar 2020 11:59:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.46] X-ClientProxiedBy: SFHDAG5NODE1.st.com (10.75.127.13) To SFHDAG3NODE1.st.com (10.75.127.7) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-26_02:2020-03-26,2020-03-26 signatures=0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/26/20 1:01 AM, Joe Perches wrote: > On Wed, 2020-03-25 at 14:31 +0100, Jiri Slaby wrote: >> The question was exactly about that: can a compiler optimize it to a >> bare number or will strlen call remain there? > > $ cat str.c > #include > > int foo(void) > { > return strlen("abc"); > } > > $ gcc -c -O2 str.c > $ objdump -d str.o > str.o: file format elf64-x86-64 > > > Disassembly of section .text: > > 0000000000000000 : > 0: f3 0f 1e fa endbr64 > 4: b8 03 00 00 00 mov $0x3,%eax > 9: c3 retq > > same result with arm gcc using -O1 or -Og: str.o: file format elf32-littlearm Disassembly of section .text: 00000000 : 0: e3a00003 mov r0, #3 4: e12fff1e bx lr So in conclusion replacing sizeof by srlen even if not optimized in -o0, right? Thanks, Arnaud