* 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