tree-scalar-evolution.c (instantiate_parameters_1): An SSA_NAME defined in a loop at depth 0 is invariant.

	* tree-scalar-evolution.c (instantiate_parameters_1): An SSA_NAME
	defined in a loop at depth 0 is invariant.
	* tree-chrec.c (evolution_function_is_invariant_rec_p): Ditto.
	* tree-ssa-loop-ivopts.c (expr_invariant_in_loop_p): Should never
	be called at loop depth 0.

From-SVN: r132835