[Bug middle-end/126418] [17 regression] PR113894 introduces new UB in optimized code

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126418

--- Comment #3 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 65296
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65296&action=edit
Patch which I am testing

This fixes all 3 patterns including the one for PR 123514 .