[Bug tree-optimization/106722] bogus uninit warning in tree-vect-loop-manip.cc

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106722

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The uninit code already handles this but it runs into its MAX_CHAIN_LEN path
discovery limit.

upping that by one fixes the reduced testcase, upping it to 8 (from 5) fixes
original preprocessed source.