From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8714 invoked by alias); 7 Nov 2011 19:06:18 -0000 Received: (qmail 8705 invoked by uid 22791); 7 Nov 2011 19:06:17 -0000 X-SWARE-Spam-Status: No, hits=-7.5 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD,SPF_HELO_PASS X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 07 Nov 2011 19:06:02 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id pA7J610h002188 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 7 Nov 2011 14:06:02 -0500 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id pA7J619j019914; Mon, 7 Nov 2011 14:06:01 -0500 Received: from [10.3.113.8] ([10.3.113.8]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id pA7J60xE014348; Mon, 7 Nov 2011 14:06:00 -0500 Message-ID: <4EB82C17.2030606@redhat.com> Date: Mon, 07 Nov 2011 19:14:00 -0000 From: Jeff Law User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 MIME-Version: 1.0 To: Jakub Jelinek CC: gcc-patches Subject: Re: RFA: New pass to delete unexecutable paths in the CFG References: <4EB7AAF6.6060702@redhat.com> <20111107100700.GH27375@tyan-ft48-01.lab.bos.redhat.com> In-Reply-To: <20111107100700.GH27375@tyan-ft48-01.lab.bos.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes 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: 2011-11/txt/msg01039.txt.bz2 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 11/07/11 03:07, Jakub Jelinek wrote: > On Mon, Nov 07, 2011 at 02:55:02AM -0700, Jeff Law wrote: >> [ Working virtually from Hawaii tonight... :-) ] > > ;) > >> You might legitimately wonder how often this triggers. A GCC >> 4.6.0 checking-enabled compiler sees a .64% codesize improvement >> from this optimization. That's an awful lot of unexecutable >> code. The NULL references come from the VEC implementation and a >> variety of other sources. > > I'd say it is a good idea, though I wonder if the gate shouldn't > also use && flag_delete_null_pointer_checks or at least if the > default for this new option shouldn't be based on > flag_delete_null_pointer_checks. -fno-delete-null-pointer-checks is > documented for quite some time as an option which allows NULL > pointer dereferences (and AFAIK AVR uses it) and people who use > that option will most likely want to disable this optimization > too. Yea, I'd been back and forth on this too -- I don't like gating on the null-pointer-check flag, but I agree that folks using - -fno-delete-null-... probably aren't going to want the new optimization either. I'll put on my thinking cap and see if I can come up with a good name that encompasses both classes of optimization without getting overly broad. jeff -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJOuCwXAAoJEBRtltQi2kC7I6UH/2PRnCZxPCHvImghz8IN3ThX IANY9jCSqRzzsebWtTwZ9Y0XE6uQhMpEx/98/ZFZ96OC8rrQkoYR+Jf4DOAP82ja SMDpBETK6BZ7Y/bMKgzJA/QfIlxIcRNScGqZg+F+C3WPqJADHAxCmWGqx/c4/Mwz aylaEBVi/7klqxpmxlkSeN6n0whXf8zL/XmTovpro/6B3oiJaVd1diyrJl3s9vL4 BwjvsbA8ZosLPVCcdLY+9OWjhlnwbOxQQ/xzN8g7knPGNVhe4pXaBmzNiPXGKzrN 1qteyLNdVvnOWj/h1w9a3Ew2EJ3eLUXTytM5BjDfA3gF9Jd1umN81Js+Z/sBRXA= =W7V6 -----END PGP SIGNATURE-----