From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4177 invoked by alias); 13 Apr 2013 01:44:31 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 4147 invoked by uid 48); 13 Apr 2013 01:44:28 -0000 From: "andrewjcg at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/56493] Performance regression in google dense hashmap Date: Sat, 13 Apr 2013 01:44:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: andrewjcg at gmail dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 X-SW-Source: 2013-04/txt/msg01330.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56493 --- Comment #10 from Andrew Gallagher 2013-04-13 01:44:27 UTC --- I did several attempts at bisecting this. Whenever I (hackily) reverted the change which caused the regression, it just popped up a few hundred revs later. This seems to be gcc assigning new weights to functions, which determines whether the functions is early inlined or not. So I *think* this is really an early inlining v. late inlining issue, and we happened to get lucky with the weights that 4.6 selected (I don't think there is a really effective way for gcc to predict how subsequent optimizations will/can benefit by early inlining). Also, as far as I can see, there is no way to force early inlining (other than switching to macros).