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Wed, 28 Oct 2020 18:22:43 +0000 (GMT) Received: from [9.160.17.83] (unknown [9.160.17.83]) by b03ledav003.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 28 Oct 2020 18:22:43 +0000 (GMT) Subject: Re: [PATCH v2 3/6] configure: add option to enable LTO To: Paolo Bonzini , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20201023200645.1055-1-dbuono@linux.vnet.ibm.com> <20201023200645.1055-4-dbuono@linux.vnet.ibm.com> <7aa00aba-ff8c-252a-899a-45ef4db7cc6e@redhat.com> <20201026155006.GE496050@redhat.com> <756e6060-394f-fe4a-47f2-2601b6e54a45@linux.vnet.ibm.com> <20201027151744.GF529052@redhat.com> <606b3283-25e5-329a-7d02-4d3d39383c73@linux.vnet.ibm.com> <0b7e524f-59f5-a7b3-7e4f-608042f0bd4f@redhat.com> From: Daniele Buono Message-ID: <718a0446-09f5-9e45-5f64-e22a72708e67@linux.vnet.ibm.com> Date: Wed, 28 Oct 2020 14:22:41 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <0b7e524f-59f5-a7b3-7e4f-608042f0bd4f@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-10-28_08:2020-10-28, 2020-10-28 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 impostorscore=0 phishscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0 lowpriorityscore=0 bulkscore=0 clxscore=1015 adultscore=0 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2010280118 Received-SPF: none client-ip=148.163.156.1; envelope-from=dbuono@linux.vnet.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/28 14:22:56 X-ACL-Warn: Detected OS = Linux 3.1-3.10 [fuzzy] X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.921, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Alexander Bulekov , Thomas Huth , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" If LTO is enabled with the wrong linker/ar: - with the checks, it will exit at configure with an error. I can change this in a warning and disabling LTO if preferred. - without the checks compilation will fail If LTO is enabled with the wrong compiler (e.g. old gcc), you may get a bunch of warnings at compile time, and a binary that won't pass some of the tests in make check. On 10/28/2020 2:44 AM, Paolo Bonzini wrote: > On 27/10/20 21:42, Daniele Buono wrote: >> Ok, no problem. I can definitely disable the check on GCC. >> >> Paolo, would you like me to disable checks on AR/linker for lto too? >> If so, should I add some of this information on a document, perhaps >> docs/devel/lto.rst, so it is written somewhere for future uses? > > I am not sure of the effects. Does it simply effectively disable LTO or > is it something worse? > > I'll look into the SCSI issue. > > Paolo >