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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libffi/102923] [12 Regression] powerpc64 (BE) linux all
 languages bootstrap broken after libffi 3.4.2 import.
Date: Mon, 25 Oct 2021 15:59:20 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102923

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #4)
> > At least in linux64_closure.S, perhaps guarding it with #ifdef __VEC__ =
might
> > be ok, because the C code will not use that code if __VEC__ isn't defin=
ed:
> > #elif !defined(__VEC__)
> >   /* If compiled without vector register support (used by assembly)... =
*/
> >   if ((cif->abi & FFI_LINUX_LONG_DOUBLE_IEEE128) !=3D 0)
> >     return FFI_BAD_ABI;
> > But not sure about linux64.S if it doesn't suffer from the same problem.
>=20
> Note that __VEC__ does not mean the current CPU can execute those insns,
> of course, so these #ifdefs are only good if you compile this file twice,
> or similar?

Sure.  I think the expectation is that one gets the ieee128 long double sup=
port
in libffi only if libffi is built with -mcpu=3Dpower8 (or -mcpu=3Dpower7 or=
 -mvsx).
And the assumption is that the *.S files are compiled with the same
-mcpu=3D/-mvsx flags as the C files.
So the only question is if all the lvx/stvx instructions are in code path t=
hat
will not be reached when __VEC__ support isn't seen on the C side.
The whole inital patch is:
https://github.com/libffi/libffi/commit/73dd43afc8a447ba98ea02e9aad4c6898dc=
77fb0=