[Bug tree-optimization/66975] parloops to handle signed int reductions

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66975

--- Comment #1 from vries at gcc dot gnu.org ---
This ( https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02064.html ) patches fixes
the problem for operations that do not overflow, f.i. min and max.