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 1AD043858404 for ; Wed, 29 Sep 2021 12:28:34 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1AD043858404 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-72-v_pVl1wcN_yoo4KgbAuqQw-1; Wed, 29 Sep 2021 08:28:32 -0400 X-MC-Unique: v_pVl1wcN_yoo4KgbAuqQw-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 477ED102CB73; Wed, 29 Sep 2021 12:28:31 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.193.109]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9D7A31009962; Wed, 29 Sep 2021 12:28:24 +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 18TCSK7r370325 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 29 Sep 2021 14:28:21 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 18TCSJJw370324; Wed, 29 Sep 2021 14:28:19 +0200 Date: Wed, 29 Sep 2021 14:28:19 +0200 From: Jakub Jelinek To: Jonathan Wakely Cc: Thomas Rodgers , Thomas Rodgers , libstdc++ , gcc Patches , Thomas Rodgers Subject: Re: [PATCH] libstdc++: Clear padding bits in atomic compare_exchange Message-ID: <20210929122819.GN304296@tucnak> Reply-To: Jakub Jelinek References: <20210923180837.633173-1-rodgert@appliantology.com> <20210927141031.651313-1-rodgert@appliantology.com> 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=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.7 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: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 29 Sep 2021 12:28:35 -0000 On Wed, Sep 29, 2021 at 01:13:46PM +0100, Jonathan Wakely via Gcc-patches wrote: > But I think that's OK, as I think the built-in is > smart enough to be a no-op for types with no padding. Yes. The only effect it will have is that during the initial optimization passes the variable/parameter will be addressable where without the call and __addressof it wouldn't be; but as soon as __builtin_clear_padding is folded to nothing if there is no padding or something if there is (which happens quite early) and TODO_update_address_taken is done at the end of some pass, it will no longer be addressable (unless something different keeps taking its address). Jakub