ppc64 ABI

[Justin Cormack <justin@specialbusservice.com>]

I am looking at doing a ppc64 port, and after some discussion on irc
last night wondering which ABI to port to.

ppc64 has two ABIs:
v1: as documented here
http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html
Slightly odd, as has function descriptors, so you cant just reference
a function pointer, mainly makes asm code messier as needs a header
for every function.
Traditionally bigendian. Fedora and Gentoo do distros, not sure there
are any others; FreeBSD support also exists.

v2, usually known as powerpc64le, helpfully. It is not little endian
exclusively, but there are no existing distros that are big endian.
Aim was to make it much closer to a standard ABI, so function pointers
are gone. IBM has been pushing this, and there are RedHat and Ubuntu
releases, targeting POWER8. (Which also means Ubuntu ships with cross
compilers for it).

I was thinking of doing a v1 port first then v2, partly as I have
little endian only hardware (Apple G5 running Fedora; Fedora has
recently dropped support though; ten years old but dual G5 is still
decent hardware). However maybe I should just skip to v2; I do have
access to hardware. In principal could then produce a bigendian Musl
distro for G5... IBM have been spending a fair amount of time making
sure software works with v2.

Both have 16 byte long double oddness.

Thoughts?