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 [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 9FE143858C50 for ; Thu, 9 Feb 2023 16:20:58 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 9FE143858C50 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675959658; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type; bh=D44J8R59HM/ErNo52aXMciB7lOQQoTyKnzCuvilRz8Q=; b=XC+TKHELdw0REY8rF/jKe/mHBjqmwhPAqJS+E0vVwXJzfMjBZZUGEjxI4KXXxQAwFtB5k5 YrAOGyz0WezpZ9NSMksvBJWDmWTZEAz2HipBInfcog/O1n8SDTTXYSExyE70b0/r5FxA+u cix2EibxgOfPQp1E8ISvOlIYT0RB3N8= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-389-kcqi7WnlPMiqoOBk1S13vQ-1; Thu, 09 Feb 2023 11:20:54 -0500 X-MC-Unique: kcqi7WnlPMiqoOBk1S13vQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6D82C3C0E462; Thu, 9 Feb 2023 16:20:54 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.223]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2AFA31121314; Thu, 9 Feb 2023 16:20:54 +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 319GKpir4060595 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 9 Feb 2023 17:20:52 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 319GKolT4060594; Thu, 9 Feb 2023 17:20:50 +0100 Date: Thu, 9 Feb 2023 17:20:50 +0100 From: Jakub Jelinek To: gcc-patches@gcc.gnu.org, Gerald Pfeifer Subject: [wwwdocs] gcc-13/changes.html: Document C++ -fexcess-precision=standard Message-ID: Reply-To: Jakub Jelinek MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 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=-3.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_SHORT,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hi! Martin Liska mentioned that porting_to.html doesn't mention the C++ excess precision changes. Not really sure if porting_to should document those, but I think changes.html certainly should. And perhaps porting_to could have some examples and link to this spot in changes. Ok for wwwdocs? --- a/htdocs/gcc-13/changes.html +++ b/htdocs/gcc-13/changes.html @@ -230,6 +230,21 @@ a work-in-progress.

C++

    +
  • Excess precision support (which has been available in C since GCC 4.5) + has been implemented for C++ as well. It is enabled by default + in strict standard modes like -std=c++17, where it + defaults to -fexcess-precision=standard, while in GNU + standard modes like -std=gnu++20 it defaults to + -fexcess-precision=fast. The option affects mainly + IA-32/x86-64 where when defaulting to x87 math and in some cases on + Motorola 68000 float and double expressions + are evaluated in long double precision and S/390, System z, + IBM z Systems where float expressions are evaluated in + double precision. Also, on several architectures where + std::float16_t or std::bfloat16_t types + are supported those are evaluated in float precision. + -fexcess-precision=fast restores previous behavior. +
  • Several C++23 features have been implemented:
    • P2324R1, Labels at the end of Jakub