'Compile the given function both without and with rewrites enabled.'

def _compile_function(self, fn, arg_tys):

    control_pipeline = RewritesTester.mk_no_rw_pipeline(arg_tys)
    cres_0 = control_pipeline.compile_extra(fn)
    control_cfunc = cres_0.entry_point
    test_pipeline = RewritesTester.mk_pipeline(arg_tys)
    cres_1 = test_pipeline.compile_extra(fn)
    test_cfunc = cres_1.entry_point
    return (control_pipeline, control_cfunc, test_pipeline, test_cfunc)
