From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12743 invoked by alias); 30 Nov 2008 11:40:15 -0000 Received: (qmail 12343 invoked by uid 48); 30 Nov 2008 11:38:53 -0000 Date: Sun, 30 Nov 2008 11:40:00 -0000 Message-ID: <20081130113853.12342.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug target/38306] [4.4 Regression] 15% slowdown of computational kernel In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "rguenth 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: 2008-11/txt/msg02625.txt.bz2 ------- Comment #2 from rguenth at gcc dot gnu dot org 2008-11-30 11:38 ------- Due to the high density of branches in the code this is easily a code layout and/or padding issue. Different architectures have different constraints on their decoders and branch predictors related to branch density. Core introduces other branch limitations for loops that engage the loop stream detector. We do not at all try to properly optimize (or even model) this apart from inserting nops. YMMV with -fschedule-insns. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38306