[Bug target/109007] building for POWER8 leaks into POWER9 ISA with g++ 11.3 (cross-compiler on x86_64 host)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109007

--- Comment #16 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #15)
> (In reply to bugreporter66 from comment #14)
> > I should be able to workaround that by emulating all LE targets on POWER9,
> > with a comment that building for POWER8 natively on target should work too.
> 
> If you want to default to Power9 but still support Power8 (on builds that use
> -mcpu=power8), you need to set up appropriate multilibs.  If you want that,
> please do a feature request for that?  As a new PR, not hidden inside this
> one please :-)

Or just make sure the libraries are still built with -mcpu=power8 even when the
compiler defaults to something else.
That said, neither multilibs nor just making sure libraries are built with
-mcpu=power8 can help with libraries outside of gcc (unless they are built as
multilibs or with the extra flags).
I'd say though that if you want to use distro packages of a distro that
switched to power9, then just live with it and don't try to run it on power8 or
power8 emulation,
or switch to a different distro which still supports power8 (many still do), or
build gcc and all the needed libraries yourself.