[Bug rtl-optimization/67828] [6 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67828

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Use ssa_undefined_value_p (..., true), otherwise looks sensible.  I suppose
we could unswitch on the value if the condition is always executed in the loop
but then that's hardly a useful optimization (on undefined values).