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 F17F3389EC49 for ; Fri, 6 May 2022 14:47:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org F17F3389EC49 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-640-g65olhi0NduKAZjJcJW4GA-1; Fri, 06 May 2022 10:47:43 -0400 X-MC-Unique: g65olhi0NduKAZjJcJW4GA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0DABF1014A63; Fri, 6 May 2022 14:47:43 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C41E854CE3A; Fri, 6 May 2022 14:47:42 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.16.1/8.16.1) with ESMTPS id 246ElexQ2189438 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 6 May 2022 16:47:40 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 246EldqM2189437; Fri, 6 May 2022 16:47:39 +0200 Date: Fri, 6 May 2022 16:47:39 +0200 From: Jakub Jelinek To: Matthias Gehre Cc: "gcc@gcc.gnu.org" Subject: Re: [RFC] Adding =?iso-8859-1?Q?division?= =?iso-8859-1?Q?=2Fmodulo_on_arbitrary_precision=A0integers=A0to=A0libgcc?= Message-ID: Reply-To: Jakub Jelinek References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 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=-4.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE 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: gcc@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 May 2022 14:47:48 -0000 On Fri, May 06, 2022 at 02:09:21PM +0000, Matthias Gehre via Gcc wrote: > /// \param quo The quotient represented by n words. Must be non-null. > /// \param rem The remainder represented by n words. Must be non-null. > /// \param a The dividend represented by n + 1 words. Must be non-null. > /// \param b The divisor represented by n words. Must be non-null. > > /// \note The word order is in host endianness. > /// \note Might modify a and b. > /// \note The storage of 'a' needs to hold n + 1 elements because some > /// implementations need extra scratch space in the most significant word. > /// The value of that word is ignored. > void __udivmodei5(uint32_t *quo, uint32_t *rem, uint32_t *a, > uint32_t *b, unsigned n); > > /// Computes the signed division of a / b. > /// See __udivmodei5 for details. > void __divmodei5(uint32_t *quo, uint32_t *rem, uint32_t *a, uint32_t *b, > unsigned n); Sizes certainly should be with size_t, not unsigned type. Rather than uint32_t, wouldn't using the word size (64-bit for lp64, 32-bit for ilp32) be better? And I really don't like the N + 1 stuff you're proposing, at least for _BigInts that would be represented as an array of those word etc. elements from least to most significant (or vice versa? That really needs to be specified too), if they are same precision having to copy one of them just to get the extra scratch is bad. Jakub