From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17389 invoked by alias); 28 Jun 2010 18:21:25 -0000 Received: (qmail 17372 invoked by uid 22791); 28 Jun 2010 18:21:24 -0000 X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mail.codesourcery.com (HELO mail.codesourcery.com) (38.113.113.100) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 28 Jun 2010 18:21:21 +0000 Received: (qmail 11462 invoked from network); 28 Jun 2010 18:21:19 -0000 Received: from unknown (HELO ?84.152.253.170?) (bernds@127.0.0.2) by mail.codesourcery.com with ESMTPA; 28 Jun 2010 18:21:19 -0000 Message-ID: <4C28E7FE.4000806@codesourcery.com> Date: Mon, 28 Jun 2010 19:34:00 -0000 From: Bernd Schmidt User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.10) Gecko/20100625 Thunderbird/3.0.5 MIME-Version: 1.0 To: Ian Lance Taylor CC: Eric Botcazou , gcc-patches@gcc.gnu.org, "Vladimir N. Makarov" Subject: Re: A few simple DImode improvements References: <4C2549D4.10608@codesourcery.com> <201006272336.56278.ebotcazou@adacore.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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 X-SW-Source: 2010-06/txt/msg02919.txt.bz2 On 06/28/2010 08:05 PM, Ian Lance Taylor wrote: > It's superfluous for a simple example like this one, but it's not > clearly superfluous in all cases. If register 68 here should wind up > being allocated to a floating point register which can't be SUBREG'ed, > then my concern is that taking a SUBREG is going to make it harder to > allocate the register correctly. In other words, the bitmap is not > irrelevant; it's a proxy for non-SImode register classes. That however applies to only one case in which bits can be set in that bitmap, the SUBREG case in find_decomposable_subregs. The normal case, I think, is that these bits come from occurrences of the reg that are in NOT_SIMPLE_MOVE, and I think this is irrelevant here. Do we need to keep track of two different bitmaps? > I don't know > whether this a concern with IRA; can IRA allocate a DImode pseudo to a > floating point register if there are SImode SUBREGs of it? The old > register allocator wouldn't, and you could wind up with a bunch of > reloads. I don't know whether IRA would do that or whether it can determine the costs correctly; I can't find anything right now which would deal with this case. Bernd