[Bug tree-optimization/96881] [8/9/10/11 Regression] Clobbers on NULL vs. DCE since r8-1519

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96881

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This PR should cover the CDDCE part of PR96722, e.g. as mentioned in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96722#c6