[Bug rtl-optimization/92656] The zero_extend insn can't be eliminated in the combine pass

[wilson at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92656

--- Comment #5 from Jim Wilson <wilson at gcc dot gnu.org> ---
A rewrite using dataflow would be better of course.  I'm just trying to
understand the problem with this testcase better, and maybe find a simple
solution, but I don't think that there is one.  The workarounds I see just make
the code more complicated and add more risk of something else going wrong.