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 605CC396E014 for ; Wed, 25 Nov 2020 20:27:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 605CC396E014 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-445-0ILR3IGgMNu7c1Y4_bY9rA-1; Wed, 25 Nov 2020 15:27:16 -0500 X-MC-Unique: 0ILR3IGgMNu7c1Y4_bY9rA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 415C0185E48A; Wed, 25 Nov 2020 20:27:15 +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 0808960854; Wed, 25 Nov 2020 20:27:14 +0000 (UTC) Subject: Re: [16/23] recog: Add a way of temporarily undoing changes To: gcc-patches@gcc.gnu.org, richard.sandiford@arm.com References: From: Jeff Law Message-ID: <9686974b-fb4e-5d87-2962-a08f87c75c33@redhat.com> Date: Wed, 25 Nov 2020 13:27:14 -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 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit 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 20:27:19 -0000 On 11/13/20 1:19 AM, Richard Sandiford via Gcc-patches wrote: > In some cases, it can be convenient to roll back the changes that > have been made by validate_change to see how things looked before, > then reroll the changes. For example, this makes it possible > to defer calculating the cost of an instruction until we know that > the result is actually needed. It can also make dumps easier to read. > > This patch adds a couple of helper functions for doing that. > > gcc/ > * recog.h (temporarily_undo_changes, redo_changes): Declare. > * recog.c (swap_change, temporarily_undo_changes): New functions. > (redo_changes): Likewise. OK...  But... + > +/* Temporarily undo all the changes numbered NUM and up, with a view > + to reapplying them later. The next call to the changes machinery > + must be: > + > + redo_changes (NUM) > + > + otherwise things will end up in an invalid state. */ It'd be nice if we had state validation in the other routines. Somebody is likely to mess this up at some point... jeff