This is the mail archive of the
`libc-alpha@sourceware.org`
mailing list for the glibc project.

Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|

Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |

Other format: | [Raw text] |

*From*: Richard Guenther <rguenther at suse dot de>*To*: "Joseph S. Myers" <joseph at codesourcery dot com>*Cc*: Andreas Jaeger <aj at suse dot de>, libc-alpha at sources dot redhat dot com*Date*: Wed, 2 May 2012 16:55:23 +0200 (CEST)*Subject*: Re: [PATCH] Use -frounding-math for math testsuite*References*: <hor4v2ah12.fsf@byrd.suse.de> <Pine.LNX.4.64.1205021400380.27126@digraph.polyomino.org.uk><Pine.LNX.4.64.1205021427420.27126@digraph.polyomino.org.uk><201205021644.05286.aj@suse.de> <Pine.LNX.4.64.1205021446430.27126@digraph.polyomino.org.uk>

On Wed, 2 May 2012, Joseph S. Myers wrote: > On Wed, 2 May 2012, Andreas Jaeger wrote: > > > On Wednesday, May 02, 2012 16:32:23 Joseph S. Myers wrote: > > > On Wed, 2 May 2012, Joseph S. Myers wrote: > > > > Please commit this. Strictly we should compile all the libraries with > > > > -frounding-math as well, since library functions may be called in any > > > > rounding mode (and without -frounding-math, round-to-nearest is > > > > assumed); the only things for which it's not needed are the > > > > miscellaneous executables, and those testcases (i.e. all except the > > > > ones this patch addresses) that don't change the rounding mode. > > > > > > Incidentally, compiling libraries with -frounding-math should fix bugs > > > such as <http://sourceware.org/bugzilla/show_bug.cgi?id=10846> with > > > missing underflow exceptions (it's still a GCC bug that it folds these > > > underflowing operations with -ftrapping-math -fno-rounding-math, but > > > -frounding-math works around the GCC bug by disabling that folding since > > > the result is inexact). > > > > Do you really mean all libraries - or just the math subdirectory? > > I mean all libraries - every shared object that glibc installs, as opposed > to ones built only as part of the testsuite (for which it is unnecessary, > if harmless). For most of them it won't make a practical difference (code > generated ought to be unchanged), in that they don't actually do floating > point, but there's the odd bit outside libm where rounding modes are > relevant (there are open bugs about strtod and printf not respecting them > ... although since those work with integer operations, it's likely > -frounding-math won't actually affect the code generated for them). There is also -fsignalling-nans which is off by default, too. Not sure if that makes a difference though, but GCC for example folds x + 0.0 to x with the default setting. Richard. -- Richard Guenther <rguenther@suse.de> SUSE / SUSE Labs SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 GF: Jeff Hawn, Jennifer Guild, Felix ImendÃ¶rffer

**Follow-Ups**:**Re: [PATCH] Use -frounding-math for math testsuite***From:*Andreas Jaeger

**Re: [PATCH] Use -frounding-math for math testsuite***From:*Joseph S. Myers

**References**:**[PATCH] Use -frounding-math for math testsuite***From:*Andreas Jaeger

**Re: [PATCH] Use -frounding-math for math testsuite***From:*Joseph S. Myers

**Re: [PATCH] Use -frounding-math for math testsuite***From:*Joseph S. Myers

**Re: [PATCH] Use -frounding-math for math testsuite***From:*Andreas Jaeger

**Re: [PATCH] Use -frounding-math for math testsuite***From:*Joseph S. Myers

Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|

Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |