* Robert Scheck:
Trying to follow the path on how to get Fedora for ppc64le to a
"POWER-Pi",
I had to learn that glibc developers seem to treat IBM POWER9 strictly equal
to ABI rules rather handling the different features more fine granulated. My
understanding here might be imprecise or wrong, this is what I understood
and I'm no expert at this topic. Nevertheless I'm trying to precise it a bit
more:
The IBM Power ISA Version 3.1 [10] specifies on page 8 compliancy subsets,
where the Linux Compliancy Subset (LCS) is explained on page 10 ff. Page 11
refers specifically to the "Scalar Float Optional Features" and mentions in
the first row of the table VSX. However what seems to be implemented e.g.
in glibc is something like "#ifdef POWER9" rather "#ifdef
HARDWAREFEATURE",
which effectively makes VSX support mandatory rather optional.
The OpenPOWER 64-Bit ELF V2 ABI Specification makes VSX support
non-optional, as far as I can tell. If it does not, that would be a bug
in the document because it's definitely the intent.
It is possible to define a different ABI without VSX support, but it
would have a different GNU triplet (not powerpc64le-*-linux-gnu) and a
different RPM architecture (not ppc64le).
The first step would be to work with the OpenPOWER Foundation to define
that new ABI. Then port the GNU and LLVM toolchains to it. Afterwards,
a new Fedora architecture can be brought up if the Fedora project
supports adding the architecture.
Thanks,
Florian
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