From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30026 invoked by alias); 15 Sep 2006 21:28:30 -0000 Received: (qmail 29998 invoked by alias); 15 Sep 2006 21:28:23 -0000 Date: Fri, 15 Sep 2006 21:28:00 -0000 Message-ID: <20060915212823.29997.qmail@sourceware.org> From: "joseph at codesourcery dot com" To: glibc-bugs@sources.redhat.com In-Reply-To: <20060609223502.2749.sjmunroe@us.ibm.com> References: <20060609223502.2749.sjmunroe@us.ibm.com> Reply-To: sourceware-bugzilla@sourceware.org Subject: [Bug ports/2749] powerpc32 does not build --without-fp X-Bugzilla-Reason: CC Mailing-List: contact glibc-bugs-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: glibc-bugs-owner@sourceware.org X-SW-Source: 2006-09/txt/msg00074.txt.bz2 List-Id: ------- Additional Comments From joseph at codesourcery dot com 2006-09-15 21:28 ------- Subject: Re: powerpc32 does not build --without-fp On Fri, 15 Sep 2006, jakub at redhat dot com wrote: > glibc on many arches doesn't have a standard conforming fma(3) - for float Yes - that's what the Debian bug report I mentioned is about. A new bug report should probably be opened in glibc Bugzilla for this issue. > just using double multiplication and addition should be good enough, but The standard says the result is rounded once, so double rounding isn't correct, but still a lot better than what we have right now. > especially for long double the current implementation is wrong. So, if there was > a soft-fp FMA that could be used on all the targets that can't do this in > hardware, it would be great. To do it for long double you'd need to add more operations to op-8.h (and invent an oct-float type), since you need an intermediate type with twice the precision. Also you'd need to add appropriate packing/unpacking for IBM long double (which soft-fp doesn't natively support). We do have various sfp-machine.h files for targets not currently using soft-fp sitting around and ready to use as part of using soft-fp for generic fma (on all targets without fma instructions). Now, we have the immediate problem that soft-fp patches are very hard to get into glibc (I have one unreviewed from June, bug 2831) and the same applies to other generic fixes to mathematical functions (bug 2592, likewise fix waiting since June) - and the glibc patches attached to this bug report have also mostly been ready for some time to go in as a clear improvement on the present state of affairs (with any subsequent fixes likely to be comparatively small and confined to either soft-fp or ports). So while I've considered generically fixing fma in glibc and adding appropriate testcases, I wouldn't be confident of such fixes actually getting anywhere. -- http://sourceware.org/bugzilla/show_bug.cgi?id=2749 ------- You are receiving this mail because: ------- You are on the CC list for the bug, or are watching someone who is.