[Bug libffi/102923] [12 Regression] powerpc64 (BE) linux all languages bootstrap broken after libffi 3.4.2 import.

["segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102923

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #1)
> The stvx stuff is guarded by #ifdef __VEC__, so perhaps the lvx stuff should
> be too, or there should be .machine push; .machine power7; ... .machine pop;
> or something similar around it?

Just
        .machine altivec
is enough, no push/pop shenanigans needed.

This can be either inside or outside an #ifdef __VEC__ block, just
personal style preference really :-)

I would put it at the start of the file.

> 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 defined:
> #elif !defined(__VEC__)
>   /* If compiled without vector register support (used by assembly)... */
>   if ((cif->abi & FFI_LINUX_LONG_DOUBLE_IEEE128) != 0)
>     return FFI_BAD_ABI;
> But not sure about linux64.S if it doesn't suffer from the same problem.

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?