From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 110272 invoked by alias); 16 Dec 2015 14:18:34 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 110259 invoked by uid 89); 16 Dec 2015 14:18:34 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,SPF_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: e06smtp12.uk.ibm.com Received: from e06smtp12.uk.ibm.com (HELO e06smtp12.uk.ibm.com) (195.75.94.108) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (CAMELLIA256-SHA encrypted) ESMTPS; Wed, 16 Dec 2015 14:18:33 +0000 Received: from localhost by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 16 Dec 2015 14:18:30 -0000 Received: from d06dlp01.portsmouth.uk.ibm.com (9.149.20.13) by e06smtp12.uk.ibm.com (192.168.101.142) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Wed, 16 Dec 2015 14:18:23 -0000 X-IBM-Helo: d06dlp01.portsmouth.uk.ibm.com X-IBM-MailFrom: uweigand@de.ibm.com X-IBM-RcptTo: gcc-patches@gcc.gnu.org Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id DA58F17D805D for ; Wed, 16 Dec 2015 14:18:57 +0000 (GMT) Received: from d06av11.portsmouth.uk.ibm.com (d06av11.portsmouth.uk.ibm.com [9.149.37.252]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id tBGEIMg531391746 for ; Wed, 16 Dec 2015 14:18:22 GMT Received: from d06av11.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id tBGEIMJm032643 for ; Wed, 16 Dec 2015 07:18:22 -0700 Received: from oc7340732750.ibm.com (dyn-9-152-213-173.boeblingen.de.ibm.com [9.152.213.173]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id tBGEILZ5032627; Wed, 16 Dec 2015 07:18:21 -0700 Received: by oc7340732750.ibm.com (Postfix, from userid 500) id B095F1513; Wed, 16 Dec 2015 15:18:21 +0100 (CET) Subject: Re: [PATCH] S/390: Allow to use r1 to r4 as literal pool base. To: vogt@linux.vnet.ibm.com Date: Wed, 16 Dec 2015 14:18:00 -0000 From: "Ulrich Weigand" Cc: gcc-patches@gcc.gnu.org, krebbel@linux.vnet.ibm.com (Andreas Krebbel), Ulrich.Weigand@de.ibm.com (Ulrich Weigand) In-Reply-To: <20151216135141.GA19006@linux.vnet.ibm.com> from "Dominik Vogt" at Dec 16, 2015 02:51:41 PM MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20151216141821.B095F1513@oc7340732750.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15121614-0009-0000-0000-00000706C02F X-SW-Source: 2015-12/txt/msg01610.txt.bz2 Dominik Vogt wrote: > On Wed, Dec 16, 2015 at 01:51:45PM +0100, Ulrich Weigand wrote: > > Dominik Vogt wrote: > > > > r2 through r4 should be fine. [ Not sure if there will be many (any?) cases > > > > where one of those is unused but r5 isn't, however. ] > > > > > > This can happen if the function only uses register pairs > > > (__int128). Actually I'm not sure whether r2 and r4 are valid > > > candidates. > > > > Huh? Why not? > > Because I'm not sure it is possible to write code where r2 (r4) is > free but r3 (r5) is not - at least when s390_emit_prologue is > called. Writing code that uses r4 and r5 but not r3 was diffucult > enough: Ah, OK. I agree that it will rarely happen (it could in more complex cases where something initially uses r2 but a very late optimization pass manages to eliminate that use). However, when it is *is* free, it is a valid candidate in the sense that it would be safe and correct to use it. Bye, Ulrich -- Dr. Ulrich Weigand GNU/Linux compilers and toolchain Ulrich.Weigand@de.ibm.com