libgfortran.so SONAME and powerpc64le-linux ABI changes

[Segher Boessenkool]

On Wed, Oct 06, 2021 at 05:41:07PM +0200, Jakub Jelinek wrote:
> On Wed, Oct 06, 2021 at 10:17:44AM -0500, Segher Boessenkool wrote:
> > On Wed, Oct 06, 2021 at 08:59:53AM +0200, Thomas Koenig wrote:
> > > >That means flipping the default on all PowerPC to no longer be double-
> > > >double.  This means that you should have IEEE QP work everywhere, or the
> > > >people who do need more than double precision will have no recourse.
> > > 
> > > I think we can exclude big-endian POWER from this - they do not have
> > > IEEE QP support, correct?  So, exclude that from the SONAME change.
> > 
> > Not correct, no.  IEEE QP works fine in either endianness.
> 
> But only for Power8 or later, no?  I guess the reason why le can switch
> moreless easily (well, far from it, it is terribly hard anyway) is that
> power8 is the oldest supported ISA for le, while be can't really assume
> power8 or later.

Yes.

We can emulate it everywhere (using libquadmath for example).  This can
magically make -msoft-float work as well everywhere, btw.

> Also, seems e.g. glibc support is there only for ppc64le and not be:
> find . -name libm.abilist | xargs grep sinieee128
> ./sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libm.abilist:GLIBC_2.32 __asinieee128 F
> ./sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libm.abilist:GLIBC_2.32 __casinieee128 F
> ./sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libm.abilist:GLIBC_2.32 __csinieee128 F
> ./sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libm.abilist:GLIBC_2.32 __sinieee128 F

I don't know what the glibc situation is.  The libraries will naturally
not invest their energy in making anything work if the compiler neglects
it :-(


Segher