re PR middle-end/90796 (GCC: O2 vs O3 output differs on simple test)

re PR middle-end/90796 (GCC: O2 vs O3 output differs on simple test)

Fix PR middle-end/90796

        PR middle-end/90796
        * gimple-loop-jam.c (any_access_function_variant_p): New function.
        (adjust_unroll_factor): Use it to constrain safety, new parameter.
        (tree_loop_unroll_and_jam): Adjust call and profitable unroll factor.

testsuite/
        * gcc.dg/unroll-and-jam.c: Add three invalid and one valid case.

From-SVN: r277287