re PR tree-optimization/50802 (FAIL: gcc.c-torture/execute/arith-rand-ll.c execution at -O2 and -Os)

        PR tree-optimization/50802
        * tree-vrp.c (simplify_conversion_using_ranges): Rewrite test
        considering what happens to ranges during sign changes and/or
        intermediate narrowing conversions.

From-SVN: r181880