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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8F0D8EE49A5 for ; Mon, 21 Aug 2023 08:35:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qY0NC-00075s-68; Mon, 21 Aug 2023 04:34:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qY0NA-00075h-LI for qemu-devel@nongnu.org; Mon, 21 Aug 2023 04:34:52 -0400 Received: from mout.kundenserver.de ([212.227.126.131]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qY0N6-0001zf-3B for qemu-devel@nongnu.org; Mon, 21 Aug 2023 04:34:52 -0400 Received: from [192.168.100.1] ([82.142.8.70]) by mrelayeu.kundenserver.de (mreue010 [213.165.67.103]) with ESMTPSA (Nemesis) id 1N5FxN-1pZPOP0a9d-0117wp; Mon, 21 Aug 2023 10:34:40 +0200 Message-ID: <75b13a6f-5866-4948-00fb-fbfdb7866e3d@vivier.eu> Date: Mon, 21 Aug 2023 10:34:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: Funny results with long double denorms on m68k Content-Language: fr To: Keith Packard , qemu-devel@nongnu.org, Richard Henderson References: <87bkf1l9hf.fsf@keithp.com> From: Laurent Vivier In-Reply-To: <87bkf1l9hf.fsf@keithp.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:lGQRLX6U/YoOsDS1XOKuBeJWLU97AC02EGB4hLL5MGhs2ECKLPV t7zfuaImHpY6vpOe9907yA9OuAfaC2W0uoZSRpFTmnZ1eJ9glfLr5y69+WseQltJ104D9I/ WyvKB6KPIDseKlWn27sDcByTvTHS3FKbWUGjPKMm2yn8vSh9bdIam0AiY/BG3Aa/ZgLZtnZ bxhsb7nrYWjb0PFEpotIA== UI-OutboundReport: notjunk:1;M01:P0:F16c1T6wDUE=;W+IlWp7uAbgFQkXjx/AE4tZc5hC 8Vg0Fr63xSeNSYM8ZHKnyvngXizTke0rMNrXRj0Nw+Tt0mNCjPvD6xU1hwwp/HtXE6vwj//p1 2BRxycbDnAvbjnpEQmeVFgFpg6XhM8f0JE1q8tmPTYdtHXCdUDajIjQutwbw0qpauWiNNI+OF /sgJb4Fd5phv5BBawdzu9HQfGBHYTyncoi/UYHM0Rbz2gdfzwWFXdGtUZNZNL60A8u6bgdhvi phcxNbOgrhsA83nWe452GSkew8fL4yKyDlFwGhMtQccdmxS3g9rRNl05cWsoFdJ8dfnuzrWo3 D63dElgJB2gnipbxleJUgA44KNpH9O2F1cbd2tog9ICwhGN5cEcMMQLM6bJDiQZKaL4nW5FiI 551O7InSNWeiIBBSUMMfMXQ8yrKksnvgSAuf2vXLlPtoJa8Wmi1hjfmgev1F9y1DAxu5bTSSm dT9CqH/3DHeYHpvEB9pyAwRjh93LnMSU1KhHwZmN4FNvJCa5f/vtfL+uKxfac02jRmezQGVhI NIb35MO3N/96uI9R0g3ElkNs/KBJxyyuT2aLgxAAPx7YqjgXkq3eXCJUFVLjzya00hL7KjV2/ 0pUemQs2w7vkbc/yue/cpwXeneFWw8xCYLAkeG+AnCCttJJ4tVbxtOXehH0FgSpK6Wqn1uXok HgZoYXwvEGRgX/dDgc2jJdd+Pli1z922Ju6XxDOY7o5QBgPmoSPAxNOOKl+JZDnhOYIr3waTV QrW1NTMaUd7muTyaheEKY4FikD+Ex3wop8fh3VOt6FEPWQuKr89vyuA8Q4lB0wWV/UJQo8AiR BrDwK+Pd5SoT445N0fxIeC4p9qgjCRzKvVeqgpH4e1xQj9xiBY+xP9DH7qG+F4mFPADNyqF4k L4nWvrjQ1hPACgg== Received-SPF: none client-ip=212.227.126.131; envelope-from=laurent@vivier.eu; helo=mout.kundenserver.de X-Spam_score_int: -61 X-Spam_score: -6.2 X-Spam_bar: ------ X-Spam_report: (-6.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-4.279, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Le 20/08/2023 à 22:55, Keith Packard a écrit : > #include > #include > > #define X 0x1p+16383l > #define Y 0x1p-16446l > > static long double build_mul = X * Y; > static volatile long double x = X; > static volatile long double y = Y; > > static void > dump_ld(const char *label, long double ld) > { > union { > long double d; > struct { > uint32_t exp:16; > uint32_t space:16; > uint32_t h; > uint32_t l; > }; > } u; > > u.d = ld; > printf("%12s: % -27La 0x%04x 0x%08x 0x%08x\n", label, u.d, u.exp, u.h, u.l); > } > > int main(void) > { > long double runtime_mul = x * y; > > dump_ld("x", x); > dump_ld("y", y); > dump_ld("build_mul", build_mul); > dump_ld("runtime_mul", runtime_mul); > return 0; > } FYI, result of this program on a real hardware (q800/m68040) is: x: 0x8p+16380 0x7ffe 0x80000000 0x00000000 y: 0x0.000000000000001p-16386 0x0000 0x00000000 0x00000001 build_mul: 0x8p-66 0x3fc0 0x80000000 0x00000000 runtime_mul: 0x8p-66 0x3fc0 0x80000000 0x00000000 Thanks, Laurent