From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 85938 invoked by alias); 27 Feb 2015 00:26:20 -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 85928 invoked by uid 89); 27 Feb 2015 00:26:19 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.9 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Fri, 27 Feb 2015 00:26:18 +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 t1R0QGXb018359 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 26 Feb 2015 19:26:17 -0500 Received: from freie.home (ovpn01.gateway.prod.ext.phx2.redhat.com [10.5.9.1]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t1R0Q9Nk028233 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 26 Feb 2015 19:26:16 -0500 Received: from livre.home (livre.home [172.31.160.2]) by freie.home (8.14.8/8.14.8) with ESMTP id t1R0PfeH032165; Thu, 26 Feb 2015 21:25:41 -0300 From: Alexandre Oliva To: Jakub Jelinek Cc: Petr Machata , Richard Biener , GCC Patches Subject: Re: [PR58315] reset inlined debug vars at return-to point References: <20150225161256.GT1746@tucnak.redhat.com> <20150225212231.GX1746@tucnak.redhat.com> <20150226072315.GZ1746@tucnak.redhat.com> Date: Fri, 27 Feb 2015 01:46:00 -0000 In-Reply-To: <20150226072315.GZ1746@tucnak.redhat.com> (Jakub Jelinek's message of "Thu, 26 Feb 2015 08:23:15 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-SW-Source: 2015-02/txt/msg01675.txt.bz2 On Feb 26, 2015, Jakub Jelinek wrote: > On Wed, Feb 25, 2015 at 09:01:09PM -0300, Alexandre Oliva wrote: >> > On Wed, Feb 25, 2015 at 06:17:33PM -0300, Alexandre Oliva wrote: >> >> My measurements, for a not particularly unusual testcase, showed an >> >> overall reduction of 63% in compile time, as indicated yesterday. Now, >> >> who should bear the burden of collecting evidence to back up the claims >> >> against the change? Are those concerns enough to hold it up? >> >> > Can you e.g. run dwlocstat on some larger C++ binaries built without and >> > with your patch? I believe dwlocstat is supposed to count only the >> > instructions where the variables or parameters are in scope, so should be >> > exactly what we care about here. >> >> Erhm... I don't think that would cover the case you were worried about, >> namely inspecting variables of an inlined function while at a statement >> moved out of the function ranges. >> >> Anyway, I've run dwlocstat and inspected the results. There is indeed a >> significant reduction in the coverage, so I looked into that. > Significant reduction in the coverage should be a red flag. Ok, I looked into it further, after patching dwlocstat to dump per-variable per-range coverage/length info, so as to be able to compare object files more easily. So far, all the differences I looked at were caused by padding at the end of BBs, and by jump stmts without line numbers at the end of BBs, both right after the debug reset stmts the proposed patch introduces. I'll dig further, because so far I've only looked at a few cases. I have to figure out some way to automate the investigation of these differences, because it has been too time-intensive, and not really fruitful in terms of finding the scenarios you're concerned with. The good news is that, looking deeper into cases that appeared to leak info across loop iterations, I confirmed I was mistaken in yesterday's analysis. Phew! :-) -- Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/ You must be the change you wish to see in the world. -- Gandhi Be Free! -- http://FSFLA.org/ FSF Latin America board member Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer