Re: ppc64 ABI

[Justin Cormack <justin@specialbusservice.com>]

On 19 April 2015 at 14:54, Szabolcs Nagy <nsz@port70.net> wrote:
> * Justin Cormack <justin@specialbusservice.com> [2015-04-19 12:44:15 +0100]:
>> 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
>> v2, usually known as powerpc64le, helpfully. It is not little endian
> ...
>>
>> Both have 16 byte long double oddness.
>
> printf/scanf decimal conversion and libm are broken with ibm128
>
> if the toolchain could be configured to use ieee128 then that works
> (i see -mabi=ieeelongdouble compiler option in gcc, it seems 32bit
> powerpc sysv abi used to require ieee128 long double, but that was
> not implemented for aix and darwin so i'm not sure who uses it)
>
> 64bit long double works too and that's what musl uses on 32bit powerpc
>
> (i dont know how much code breaks if we change long double:
> i think on typical desktop/server it does not matter, but if you
> want to run some ppc optimized fortran code then it might..)

The Fedora ppc64 gcc accepts -mlong-double-64 it turns out.

Justin