From owner-freebsd-current@FreeBSD.ORG Wed Mar 26 12:58:32 2003 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 010A337B407 for ; Wed, 26 Mar 2003 12:58:32 -0800 (PST) Received: from motgate.mot.com (motgate.mot.com [129.188.136.100]) by mx1.FreeBSD.org (Postfix) with ESMTP id E5A2643F75 for ; Wed, 26 Mar 2003 12:58:29 -0800 (PST) (envelope-from rittle@latour.rsch.comm.mot.com) Received: from pobox3.mot.com (pobox3.mot.com [10.64.251.242]) by motgate.mot.com (Motorola/Motgate) with ESMTP id h2QKwTZ0002799 for ; Wed, 26 Mar 2003 13:58:29 -0700 (MST) Received: [from latour.rsch.comm.mot.com (latour.rsch.comm.mot.com [145.1.80.116]) by pobox3.mot.com (MOT-pobox3 2.0) with ESMTP id NAA25153 for ; Wed, 26 Mar 2003 13:56:07 -0700 (MST)] Received: from latour.rsch.comm.mot.com (localhost.rsch.comm.mot.com [127.0.0.1])h2QKwRN8061915; Wed, 26 Mar 2003 14:58:27 -0600 (CST) (envelope-from rittle@latour.rsch.comm.mot.com) Received: (from rittle@localhost) by latour.rsch.comm.mot.com (8.12.8/8.12.8/Submit) id h2QKwR9Z061914; Wed, 26 Mar 2003 14:58:27 -0600 (CST) Date: Wed, 26 Mar 2003 14:58:27 -0600 (CST) From: Loren James Rittle Message-Id: <200303262058.h2QKwR9Z061914@latour.rsch.comm.mot.com> To: freebsd-current@freebsd.org In-Reply-To: <20030326174535.GA83816@dragon.nuxi.com> References: <20030326130118.8374.qmail@sources.redhat.com> Organization: Networks and Infrastructure Lab (IL02/2240), Motorola Labs Cc: X-Spam-Status: No, hits=-19.6 required=5.0 tests=IN_REP_TO,QUOTED_EMAIL_TEXT,REFERENCES,REPLY_WITH_QUOTES autolearn=ham version=2.50 X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.50 (1.173-2003-02-20-exp) Subject: Re: optimization/10189: pentium4 breaks suns libm code for __ieee754_pow(double x, double y) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Mar 2003 20:58:33 -0000 > Beautiful email!! Thanks David but, although the exact words are mine, I felt deja vu while writing them. I have been asked to contribute it to the gcc bug reporting docs as a warning against using the compiler in novel modes unless you actually first test it as I will describe. Then we will ask all reporters of CPU switch PRs whether they did or can do that test before attempting to stare at a full package/kernel failure mode. I will attempt to be a little more pro-active in watching the GNATS at gcc.gnu.org for FreeBSD. There appears to be an near endless supply of people that wish to add these CPU flags to kernel builds. ;-) >> Special secret #2: Although the FSF-side does want to improve all >> code generation (and I think proper PRs RE CPU switches will be >> looked at by someone given enough time) be aware that -O2 without >> special arch flags is probably the most stable for any given CPU >> for any given gcc release. Do you really want to trust a kernel >> built with optimization flags and arch flags that near zero or zero >> people have fully tested? Doubtful. However, inline with secret >> #1 and by virtual of being digital, if even one person tests it >> (i.e. yourself) and it appears OK, then it is probably safe to at >> least attempt to build a kernel and run it. > FreeBSD has for years recommended -O[1] vs. -O2. Do you think there is > value in having the GCC test suite runs you do at FreeBSD.org do runs > with both settings? Actually (slight backpettle), all of the modern DG test suite in gcc are run at the broad range of -O0,1,2,3. OTOH, by default, everyone is bootstrapping the compiler at -O2 everyday. > To also do runs with the newer CPU types? This would be quite revealing. I would like to extend the automatic regression checkers to cover that but, yow, I'm already eating a lot of cycles on those machines. Added to list of things to check. Regards, Loren