[Bug target/120870] [16/17 regression] CPython miscompiled with preserve_none and CFLAGS="-O2 -march=znver2 -ggdb3"

[sjames at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120870

--- Comment #29 from Sam James <sjames at gcc dot gnu.org> ---
I think the patch in CPython adds an optimisation and it is latent in GCC.
Trying to understand it more.