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From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/109007] building for POWER8 leaks into POWER9 ISA with
 g++ 11.3 (cross-compiler on x86_64 host)
Date: Sun, 05 Mar 2023 21:40:49 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109007

--- Comment #17 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #16)
> Or just make sure the libraries are still built with -mcpu=3Dpower8 even =
when
> the compiler defaults to something else.

That doesn't scale.

> That said, neither multilibs nor just making sure libraries are built with
> -mcpu=3Dpower8 can help with libraries outside of gcc (unless they are bu=
ilt
> as multilibs or with the extra flags).

Sure.  But this bug is about that a compiler built --with-cpu=3DX can not b=
uild
anything that can run on any older CPU (or does not have some feature that X
has, more generally).  This is a problem that we already do have a solution
for, but something we have disabled in the powerpc64le-linux subtarget
unfortunately.

> or build gcc and all the needed libraries yourself.

Yup.  But it should not be necessary to build a different GCC.=