From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25376 invoked by alias); 25 Apr 2010 12:13:44 -0000 Received: (qmail 25278 invoked by uid 48); 25 Apr 2010 12:13:24 -0000 Date: Sun, 25 Apr 2010 12:13:00 -0000 Message-ID: <20100425121324.25277.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug c++/43884] [4.4/4.5 Regression] Performance degradation for simple fibonacci numbers calculation In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "steven at gcc dot gnu dot org" 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 X-SW-Source: 2010-04/txt/msg02631.txt.bz2 ------- Comment #2 from steven at gcc dot gnu dot org 2010-04-25 12:13 ------- Confirmed on x86_64-linux by comparing gcc 4.3.3 vs. gcc 4.6.0 (r158482). The average of 10 runs on each is 5.1s with gcc 4.3.3 vs. 5.7s for gcc 4.4.2, gcc 4.5.0 and gcc 4.6.0. One interesting difference is that GCC 4.5 does not inline fib. But that shouldn't have a big impact on performance. The generated code for fib is completely different (maybe an IRA thing??), so it's hard to tell where the slow-down comes from. -- steven at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Last reconfirmed|0000-00-00 00:00:00 |2010-04-25 12:13:24 date| | Summary|Performance degradation of |[4.4/4.5 Regression] |the simple example |Performance degradation for |(fibonacci) 4.3.3->4.5.0 |simple fibonacci numbers | |calculation http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43884