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 ESMTPS id A5C563858C2D for ; Tue, 16 Aug 2022 18:08:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A5C563858C2D Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-294-9JUvwvT4Mxe1uuMpM2cZSg-1; Tue, 16 Aug 2022 14:07:56 -0400 X-MC-Unique: 9JUvwvT4Mxe1uuMpM2cZSg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C3B8E8037AA; Tue, 16 Aug 2022 18:07:55 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.41]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7AC0D492C3B; Tue, 16 Aug 2022 18:07:55 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.17.1/8.17.1) with ESMTPS id 27GI7pgf1289988 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 16 Aug 2022 20:07:52 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 27GI7nK91289987; Tue, 16 Aug 2022 20:07:49 +0200 Date: Tue, 16 Aug 2022 20:07:48 +0200 From: Jakub Jelinek To: Joseph Myers , Jason Merrill , Jonathan Wakely Cc: Michael Meissner , Peter Bergner , gcc-patches@gcc.gnu.org, David Edelsohn , Segher Boessenkool Subject: Re: [PATCH 0/5] IEEE 128-bit built-in overload support. Message-ID: Reply-To: Jakub Jelinek References: <20220805181905.GQ25951@gate.crashing.org> <20220810170316.GZ25951@gate.crashing.org> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Aug 2022 18:08:02 -0000 On Thu, Aug 11, 2022 at 08:44:17PM +0000, Joseph Myers wrote: > On Thu, 11 Aug 2022, Michael Meissner via Gcc-patches wrote: > > > In looking at it, I now believe that the type for _Float128 and __float128 > > should always be the same within the compiler. Whether we would continue to > > use the same type for long double and _Float128/__float128 remains to be seen. > > long double and _Float128 must always be different types; that's how it's > defined in C23. And when we implement C++23 P1467R9, if std::float128_t will be _Float128 under the hood, then long double and _Float128 have to remain distinct types and mangle differently, long double (and __float128 if long double is IEEE quad and __float128 exists?) need to mangle the way they currently do and _Float128 should mangle as DF128_ . ::= DF _ # ISO/IEC TS 18661 binary floating point type _FloatN (N bits) Wonder how shall we mangle the underlying type of std::bfloat16_t though. I assume e.g. for libstdc++ implementation purposes we need to have __ibm128 and __float128 types mangling as long double mangles when the -mabi={ibm,ieee}longdouble option is used, because otherwise it would be really hard to implement it. Jakub