lang.opt: Add -Wdo-subscript.

lang.opt: Add -Wdo-subscript.

2017-09-25  Thomas Koenig  <tkoenig@gcc.gnu.org>

	* lang.opt:  Add -Wdo-subscript.
	* frontend-passes.c (do_t): New type.
	(doloop_list): Use variable of do_type.
	(if_level): Variable to track if levels.
	(select_level): Variable to track select levels.
	(gfc_run_passes): Initialize i_level and select_level.
	(doloop_code): Record current level of if + select
	level in doloop_list.  Add seen_goto if there could
	be a branch outside the loop. Use different type for
	doloop_list.
	(doloop_function): Call do_intent and do_subscript; move
	functionality of checking INTENT to do_intent.
	(insert_index_t): New type, for callback_insert_index.
	(callback_insert_index): New function.
	(insert_index): New function.
	(do_subscript): New function.
	(do_intent): New function.
	(gfc_code_walker): Keep track of if_level and select_level.
	* invoke.texi: Document -Wdo-subscript.

2017-09-25  Thomas Koenig  <tkoenig@gcc.gnu.org>

	* gfortran.dg/do_subscript_1.f90: New test.
	* gfortran.dg/do_subscript_2.f90: New test.
	* gfortran.dg/gomp/associate1.f90: Add out of bounds warning.
	* gfortran.dg/predcom-1.f: Adjust loop bounds.
	* gfortran.dg/unconstrained_commons.f: Add out of bounds warning.

From-SVN: r253156