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 [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id D92593851C1A for ; Wed, 25 Nov 2020 20:13:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org D92593851C1A 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-21-a63SX55BOLa9xFmABN0g_w-1; Wed, 25 Nov 2020 15:13:01 -0500 X-MC-Unique: a63SX55BOLa9xFmABN0g_w-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 665BC1842140; Wed, 25 Nov 2020 20:13:00 +0000 (UTC) Received: from localhost.localdomain (ovpn-113-191.phx2.redhat.com [10.3.113.191]) by smtp.corp.redhat.com (Postfix) with ESMTP id 27239100239F; Wed, 25 Nov 2020 20:13:00 +0000 (UTC) Subject: Re: [05/23] Add more iterator utilities To: gcc-patches@gcc.gnu.org, richard.sandiford@arm.com References: From: Jeff Law Message-ID: <2d64a769-4e36-f688-0f12-f803a1b9298d@redhat.com> Date: Wed, 25 Nov 2020 13:12:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: 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; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Spam-Status: No, score=-5.5 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Wed, 25 Nov 2020 20:13:05 -0000 On 11/13/20 1:13 AM, Richard Sandiford via Gcc-patches wrote: > This patch adds some more iterator helper classes. They really fall > into two groups, but there didn't seem much value in separating them: > > - A later patch has a class hierarchy of the form: > > Base > +- Derived1 > +- Derived2 > > A class wants to store an array A1 of Derived1 pointers and an > array A2 of Derived2 pointers. However, for compactness reasons, > it was convenient to have a single array of Base pointers, > with A1 and A2 being slices of this array. This reduces the > overhead from two pointers and two ints (3 LP64 words) to one > pointer and two ints (2 LP64 words). > > But consumers of the class shouldn't be aware of this: they should > see A1 as containing Derived1 pointers rather than Base pointers > and A2 as containing Derived2 pointers rather than Base pointers. > This patch adds derived_iterator and const_derived_container > classes to support this use case. > > - A later patch also adds various linked lists. This patch adds > wrapper_iterator and list_iterator classes to make it easier > to create iterators for these linked lists. For example: > > // Iterators for lists of definitions. > using def_iterator = list_iterator; > using reverse_def_iterator > = list_iterator; > > This in turn makes it possible to use range-based for loops > on the lists. > > The patch just adds the things that the later patches need; it doesn't > try to make the classes as functionally complete as possible. I think > we should add extra functionality when needed rather than ahead of time. > > gcc/ > * iterator-utils.h (derived_iterator): New class. > (const_derived_container, wrapper_iterator): Likewise. > (list_iterator): Likewise. OK jeff