From owner-freebsd-current@FreeBSD.ORG Tue Sep 11 17:19:52 2012 Return-Path: Delivered-To: current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 86F9D106566C; Tue, 11 Sep 2012 17:19:52 +0000 (UTC) (envelope-from rdivacky@vlakno.cz) Received: from vlakno.cz (lev.vlakno.cz [46.28.110.116]) by mx1.freebsd.org (Postfix) with ESMTP id 413208FC16; Tue, 11 Sep 2012 17:19:51 +0000 (UTC) Received: by vlakno.cz (Postfix, from userid 1002) id 4539C7F38CB; Tue, 11 Sep 2012 19:19:48 +0200 (CEST) Date: Tue, 11 Sep 2012 19:19:48 +0200 From: Roman Divacky To: Steve Kargl Message-ID: <20120911171948.GA81334@freebsd.org> References: <20120910211207.GC64920@lor.one-eyed-alien.net> <20120911104518.GF37286@deviant.kiev.zoral.com.ua> <20120911120649.GA52235@freebsd.org> <20120911132410.GA87126@troutmask.apl.washington.edu> <504F4645.4070900@FreeBSD.org> <504F4A6B.4010001@coosemans.org> <20120911151230.GB87526@troutmask.apl.washington.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120911151230.GB87526@troutmask.apl.washington.edu> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: toolchain@FreeBSD.org, Tijl Coosemans , Dimitry Andric , current@FreeBSD.org Subject: Re: Clang as default compiler November 4th X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 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: Tue, 11 Sep 2012 17:19:52 -0000 On Tue, Sep 11, 2012 at 08:12:30AM -0700, Steve Kargl wrote: > On Tue, Sep 11, 2012 at 04:27:55PM +0200, Tijl Coosemans wrote: > > On 11-09-2012 16:10, Dimitry Andric wrote: > > > On 2012-09-11 15:24, Steve Kargl wrote: > > >> What is important is whether software built with clang functions > > >> correctly. See for example, > > >> > > >> http://math-atlas.sourceforge.net/errata.html#WhatComp > > > > > > Yes, maths support, specifically precision, is admittedly still one of > > > clang's (really llvm's) weaker points. It is currently not really a > > > high priority item for upstream. > > > > > > This is obviously something that a certain part of our userbase will > > > care a lot about, while most of the time they won't care so much about > > > licensing or politics. So those people are probably better off using > > > gcc for the time being. > > > > Does it affect the accuracy of libm functions? > > > > I'm not sure if anyone has done any extensive testing. > I've started to run some of my test codes to compare > certain functions in a clang-compiled libm, gcc-compiled > libm, and reference solutions generated from math/mpfr. > For a locally patched j0f, I found that clang gave > much worse accuracy. If I revert the local patch, > clang and gcc are to give the same results. Unfortnately, > an unpatched j0f gives 500000 ULP errors. Steve, Can you please provide a small self contained test case that shows that clang is doing worse on accuracy than gcc? So that we can analyze it and decide if it's a bug in the code or in the compiler. So far we know absolutely nothing. Thank you, Roman