[Bug tree-optimization/66678] loop counter not accurately described by vrp

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66678

--- Comment #2 from vries at gcc dot gnu.org ---
Created attachment 35878
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35878&action=edit
tentative patch