From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from eggs.gnu.org (eggs.gnu.org [IPv6:2001:470:142:3::10]) by sourceware.org (Postfix) with ESMTPS id 7B7633858D3C for ; Sat, 27 May 2023 21:24:31 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 7B7633858D3C Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=nexgo.de Authentication-Results: sourceware.org; spf=fail smtp.mailfrom=nexgo.de Received: from mr3.vodafonemail.de ([145.253.228.163]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q31On-00047X-Iw for gcc@gnu.org; Sat, 27 May 2023 17:24:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nexgo.de; s=vfde-smtpout-mb-15sep; t=1685222666; bh=13fZaM9M/z054V5NO0Wy9pDY5Pv2QCuC5JokD3zP08k=; h=Message-ID:From:To:Subject:Date:Content-Type:X-Mailer:From; b=NIuD9MjpSiHzaKlhAMepwIWafNgLm7xcYepu7+9jIVs64GL7/CyUwrjuB6reP4JJF cvAolYeSKH3p94LCsl7KwNVOv6ivyNRYguOeHL/UVm2L6bBOCuBfD6f9RSlNZOKtAM 05dR9vhPzY84Jg0Zye2biiAMPgLT4yi7B2KK71FM= Received: from smtp.vodafone.de (unknown [10.0.0.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by mr3.vodafonemail.de (Postfix) with ESMTPS id 4QTFDB3VmXz20vV for ; Sat, 27 May 2023 21:24:26 +0000 (UTC) Received: from H270 (p5b38f631.dip0.t-ipconnect.de [91.56.246.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by smtp.vodafone.de (Postfix) with ESMTPSA id 4QTFD60c3vzHnHZ for ; Sat, 27 May 2023 21:24:19 +0000 (UTC) Message-ID: <23A490318B7149D88618A7CDA2CEDB14@H270> From: "Stefan Kanthak" To: Subject: Who cares about performance (or Intel's CPU errata)? Date: Sat, 27 May 2023 23:20:20 +0200 Organization: Me, myself & IT MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MimeOLE: Produced By Microsoft MimeOLE V6.1.7601.24158 X-purgate-type: clean X-purgate: clean X-purgate-size: 704 X-purgate-ID: 155817::1685222662-F7FFE4F5-610ACB78/0/0 Received-SPF: pass client-ip=145.253.228.163; envelope-from=stefan.kanthak@nexgo.de; helo=mr3.vodafonemail.de X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9,DKIM_SIGNED=0.1,DKIM_VALID=-0.1,DKIM_VALID_AU=-0.1,DKIM_VALID_EF=-0.1,RCVD_IN_DNSWL_LOW=-0.7,SPF_HELO_NONE=0.001,SPF_PASS=-0.001,T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_FAIL,SPF_HELO_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Just to show how SLOPPY, INCONSEQUENTIAL and INCOMPETENT GCC's developers are: --- dontcare.c --- int ispowerof2(unsigned __int128 argument) { return __builtin_popcountll(argument) + __builtin_popcountll(argument >> 64) == 1; } --- EOF --- GCC 13.3 gcc -march=haswell -O3 https://gcc.godbolt.org/z/PPzYsPzMc ispowerof2(unsigned __int128): popcnt rdi, rdi popcnt rsi, rsi add esi, edi xor eax, eax cmp esi, 1 sete al ret OOPS: what about Intel's CPU errata regarding the false dependency on POPCNTs output? See https://gcc.godbolt.org/z/jdjTc3EET for comparison! FIX YOUR BUGS, KIDS! Stefan