From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83]) by sourceware.org (Postfix) with ESMTPS id 4493A3858D3C for ; Thu, 5 May 2022 14:31:49 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4493A3858D3C X-IronPort-AV: E=Sophos;i="5.91,201,1647298800"; d="scan'208";a="34880532" Received: from malt.loria.fr (HELO [152.81.9.54]) ([152.81.9.54]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2022 16:31:48 +0200 Message-ID: Date: Thu, 5 May 2022 16:31:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Content-Language: fr From: =?UTF-8?Q?St=c3=a9phane_Glondu?= To: Alexander Monakov , gcc-help@gcc.gnu.org Cc: sibid@uvic.ca, Paul Zimmermann References: <9f7e3aa9-8d46-1fbb-75b-1c8ad9a667f@ispras.ru> Subject: Re: slowdown with -std=gnu18 with respect to -std=c99 In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_NUMSUBJECT, NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-help@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-help mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 May 2022 14:31:53 -0000 As additional data points, the performance with several versions of gcc (as packaged in Debian testing/unstable): | gcc-9 | gcc-10 | gcc-11 | gcc-12 | ------------|-------|--------|--------|--------| -std=c99 | 24 | 23.5 | 23 | 23 | -std=gnu18 | 43 | 16.8 | 38 | 38 | One can see that the performance stays relatively constant with -std=c99, but varies significantly with -std=gnu18. -- Stéphane