From owner-cvs-all@FreeBSD.ORG Mon Nov 10 21:04:07 2003 Return-Path: Delivered-To: cvs-all@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 1AD3116A4CE for ; Mon, 10 Nov 2003 21:04:07 -0800 (PST) Received: from vette.gigo.com (vette.gigo.com [216.218.228.114]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9CB1943F75 for ; Mon, 10 Nov 2003 21:03:58 -0800 (PST) (envelope-from lioux@brturbo.com) Received: from 200.101.111.208 (200-101-111-208.bsace705.dsl.brasiltelecom.net.br [200.101.111.208]) by vette.gigo.com (Postfix) with ESMTP id B5A6057CB for ; Mon, 10 Nov 2003 20:52:05 -0800 (PST) Received: (qmail 26873 invoked by uid 1001); 11 Nov 2003 04:07:35 -0000 Message-ID: <20031111040735.26872.qmail@exxodus.fedaykin.here> Received: (qmail 74635 invoked from network); 26 Oct 2003 12:17:33 -0000 Received: from unknown (HELO localhost) (unknown) by unknown with SMTP; 26 Oct 2003 12:17:33 -0000 Received: from pop3.uol.com.br by localhost with POP3 (fetchmail-6.2.5) for lioux-freebsd@localhost (single-drop); Sun, 26 Oct 2003 10:17:11 -0200 (BRST) Received: from peart.uol.com.br (172.26.5.187) by mtauol7.mail.sys.intranet (5.1.071) id 3EDB5C0C01D706F4 for lioux-freebsd@uol.com.br; Sun, 26 Oct 2003 08:48:00 -0300 Received: from mx2.freebsd.org (mx2.freebsd.org [216.136.204.119]) by storm1.uol.com.br (Postfix) with ESMTP id A7F1DE09E for ; Sun, 26 Oct 2003 09:47:59 -0200 (BRST) Received: from hub.freebsd.org (hub.freebsd.org [216.136.204.18]) by mx2.freebsd.org (Postfix) with ESMTP id 0E58757127 for ; Sun, 26 Oct 2003 03:47:55 -0800 (PST) (envelope-from owner-src-committers@FreeBSD.org) Received: by hub.freebsd.org (Postfix) id D58D116A4D6; Sun, 26 Oct 2003 03:47:50 -0800 (PST) Delivered-To: lioux@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 538) id 0DAB916A4C2; Sun, 26 Oct 2003 03:47:50 -0800 (PST) Delivered-To: src-committers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A1AC016A4B3; Sun, 26 Oct 2003 03:47:18 -0800 (PST) Received: from mailout04.sul.t-online.com (mailout04.sul.t-online.com [194.25.134.18]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0276243F75; Sun, 26 Oct 2003 03:47:17 -0800 (PST) (envelope-from Alexander@Leidinger.net) Received: from fwd05.aul.t-online.de by mailout04.sul.t-online.com with smtp id 1ADjMO-0007K7-01; Sun, 26 Oct 2003 12:47:04 +0100 Received: from Andro-Beta.Leidinger.net (JO0T2EZFZez9TuWaU8qhAbhWNxHtPlKLQNCEd+XeRTXndxhP0Byk4k@[217.83.20.54]) by fmrl05.sul.t-online.com with esmtp id 1ADjMI-2Gnrf60; Sun, 26 Oct 2003 12:46:58 +0100 Received: from Magelan.Leidinger.net (Magellan [192.168.1.1]) h9QBknf5071990; Sun, 26 Oct 2003 12:46:49 +0100 (CET) (envelope-from Alexander@Leidinger.net) Received: from Magelan.Leidinger.net (netchild@localhost [127.0.0.1]) h9QBknDC059440; Sun, 26 Oct 2003 12:46:49 +0100 (CET) (envelope-from Alexander@Leidinger.net) From: Alexander Leidinger To: des@des.no (Dag-Erling =?ISO-8859-1?Q?Sm=F8rgrav?=) In-Reply-To: References: <20031026064145.18F0E2A8D5@canning.wemm.org> X-Mailer: Sylpheed version 0.9.6claws (GTK+ 1.2.10; i386-portbld-freebsd5.1) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Seen: false X-ID: JO0T2EZFZez9TuWaU8qhAbhWNxHtPlKLQNCEd+XeRTXndxhP0Byk4k@t-dialin.net Sender: owner-src-committers@FreeBSD.org Precedence: bulk X-Loop: FreeBSD.ORG cc: Jeff Roberson cc: src-committers@freebsd.org cc: cvs-all@freebsd.org cc: Peter Wemm cc: cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/i386/i386 pmap.c X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.1 List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Date: Tue, 11 Nov 2003 05:04:07 -0000 X-Original-Date: Sun, 26 Oct 2003 12:46:48 +0100 X-List-Received-Date: Tue, 11 Nov 2003 05:04:07 -0000 On Sun, 26 Oct 2003 12:13:37 +0100 des@des.no (Dag-Erling Sm=F8rgrav) wrote: > Is there any way to teach (or trick) gcc to generate a branch which > the p4 will predict correctly? First of all: ---snip--- `-fno-guess-branch-probability' Do not guess branch probabilities using a randomized model. Sometimes gcc will opt to use a randomized model to guess branch probabilities, when none are available from either profiling feedback (`-fprofile-arcs') or `__builtin_expect'. This means that different runs of the compiler on the same program may produce different object code. In a hard real-time system, people don't want different runs of the compiler to produce code that has different behavior; minimizing non-determinism is of paramount import. This switch allows users to reduce non-determinism, possibly at the expense of inferior optimization. The default is `-fguess-branch-probability' at levels `-O', `-O2', `-O3', `-Os'. ---snip--- Except instrumenting the code with "expect" or using "-fprofile-arcs" there's only the possibility to modify the code of gcc to match our existing model... Bye, Alexander. --=20 I believe the technical term is "Oops!" http://www.Leidinger.net Alexander @ Leidinger.net GPG fingerprint =3D C518 BC70 E67F 143F BE91 3365 79E2 9C60 B006 3FE7