[Bug target/71921] missed vectorization optimization

[arjan at linux dot intel.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71921

--- Comment #8 from Arjan van de Ven <arjan at linux dot intel.com> ---
Created attachment 40417
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40417&action=edit
refined test case