[Bug tree-optimization/65177] [5 Regression]: extend jump thread for finite state automata causes miscompilation

[spop at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65177

--- Comment #20 from Sebastian Pop <spop at gcc dot gnu.org> ---
Created attachment 35046
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35046&action=edit
fix

The attached patch fixes the problem by not creating diamonds in the copied
jump-thread.

I'm bootstrapping and regtesting this on x86_64-linux and I will send the patch
for review after it passes.