From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id 601313858D39 for ; Thu, 23 Sep 2021 08:09:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 601313858D39 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-514-iBfZhehNNu-pfryneSKSmA-1; Thu, 23 Sep 2021 04:08:57 -0400 X-MC-Unique: iBfZhehNNu-pfryneSKSmA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 534009F934; Thu, 23 Sep 2021 08:08:56 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.176]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4C9E910013C1; Thu, 23 Sep 2021 08:08:55 +0000 (UTC) From: Florian Weimer To: Paul Zimmermann Cc: carlos@redhat.com, libc-alpha@sourceware.org Subject: Re: Linux Plumbers Conference: GNU Tools Track: glibc BoF (notes) References: <874kabu3pr.fsf@oldenburg.str.redhat.com> Date: Thu, 23 Sep 2021 10:08:51 +0200 In-Reply-To: (Paul Zimmermann's message of "Thu, 23 Sep 2021 10:01:49 +0200") Message-ID: <87zgs3soh8.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-7.2 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP 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: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Sep 2021 08:09:01 -0000 * Paul Zimmermann: >> > thank you for the report. Where can we get more information on the >> > "ppc64le long double change"? >> > >> > Is that https://fedoraproject.org/wiki/Changes/PPC64LE_Float128_Transition? >> > On that page, by "128-bit IEEE format" you mean a 128-bit encoding, but >> > holding only 64 bits of significand (format called ldbl-96 in glibc)? >> >> Essentially it's about switching the distribution default from >> sysdeps/ieee754/ldbl-128ibm to sysdeps/ieee754/ldbl-128. >> >> The former is a pair of doubles, using Dekker's method, and the latter >> is the regular binary128 IEEE quad-precision format. > > thank you Florian for the clarification. Then "long double" in C will > map to binary128, like _Float128? Yes, but you can go back to double-double with a compiler flag if you wish (-mabi=ibmlongdouble, I think). Thanks, Florian