On Fri, Jan 14, 2022 at 04:07:08PM +0100, Dan Horák wrote:
> > Another important thing I wanted to say is that we'd like to switch
> > ppc64le from the numerically problematic IBM extended long double to
> > IEEE 754 quad long double. This is an ABI change. Some libraries
> > are already built so that they support both ABIs at the same time,
> > including glibc, libstdc++, libgcc, libgfortran etc.
> > For other libraries and binaries, the compiler, assembler and linker
> > will notice if they use long double and flag them as using either
> > IBM or IEEE long double and linker (or I think dynamic linker too)
> > might complain when things are mixed.
> > Right now the rawhide gcc still defaults to -mabi=ibmlongdouble
> > but the glibc/gcc libraries are built compatibly with both.
> > We'd like to configure gcc shortly before the mass rebuild with
> > --with-long-double-format=ieee so that it will default to
> > -mabi=ieeelongdouble, probably on a side-tag build first, and it
> > will be highly desirable to rebuild at least some of the most commonly
> > used library packages in the order of dependencies there, otherwise
> > I'd be afraid the mass rebuild could fail for way too many packages
> > (as the mass rebuild doesn't do dependency order rebuilds but just
> > goes through packages alphabetically or so).
> > Any suggestions on which packages have commonly used library packages
> > that use long double?
> > readelf -A on libraries on ppc64le prints either nothing (either
> > the library is thought not to use long double or supports both ABIs
> > transparently or hasn't been rebuilt for some years), or
> > Attribute Section: gnu
> > File Attributes
> > Tag_GNU_Power_ABI_FP: hard float, 128-bit IBM long double
> > for libraries (or binaries or object files) that use IBM long double
> > only or
> > Attribute Section: gnu
> > File Attributes
> > Tag_GNU_Power_ABI_FP: hard float, 128-bit IEEE long double
> > for IEEE long doubles.
> > So I think we want to rebuild on a side-tag packages that
> > provide shared libraries used by hundreds of other packages that
> > are
> > Tag_GNU_Power_ABI_FP: hard float, 128-bit IBM long double
> > right now.
>
> a quick&dirty scan of /usr/lib64 on my F-34 workstation shows
> many ./libQt5*
> many ./libLLVM*
> ./libgobject-2.0
> ./libgio-2.0
> ./libglib-2.0
> ./libexiv2-xmp
> ./libhwy
> ./python3.9/site-packages/numpy/*
> ./libSDL2
> ./libiberty
> ./clang/12.0.1/lib/libclang_rt.builtins-powerpc64le.a
> ./ghdl/llvm/libgrt.a
> ./libc
>
> as users of the Tag_GNU_Power_ABI_FP attribute. A vast majority of the
> hits are "Tag_GNU_Power_ABI_FP: hard float, unspecified long double"
>
> Translated to packages it is qt5-*, llvm + clang, numpy, SDL2, glib2,
> exiv2, glibc, highway
The -mabi=ieeelongdouble defaulting gcc is now in the
f36-build-side-49600 side-tag (gcc -0.5.1.fc36, same as -0.5.fc36 in
rawhide except for the different ppc64le default ABI).
Jakub
_______________________________________________
devel mailing list -- devel@lists.fedoraproject.org
To unsubscribe send an email to devel-le...@lists.fedoraproject.org
Fedora Code of Conduct:
https://docs.fedoraproject.org/en-US/project/code-of-conduct/
List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
List Archives:
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org
Do not reply to spam on the list, report it:
https://pagure.io/fedora-infrastructure
