re PR fortran/85599 (warn about short-circuiting of logical expressions for non-pure...

re PR fortran/85599 (warn about short-circuiting of logical expressions for non-pure functions)

2018-07-18  Janus Weil  <janus@gcc.gnu.org>
	    Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/85599
	* dump-parse-tree.c (show_attr): Add handling of implicit_pure.
	* frontend-passes.c (do_warn_function_elimination): Do not warn for
	pure functions.
	* gfortran.h: Add prototypes for gfc_pure_function and
	gfc_implicit_pure_function.
	* gfortran.texi: Add chapter on evaluation of logical expressions.
	* invoke.texi: Mention that -Wfunction-elimination is implied
	by -Wextra.
	* lang.opt: Make -Wextra imply -Wfunction-elimination.
	* resolve.c (pure_function): Rename to gfc_pure_function.
	(gfc_implicit_pure_function): New function.
	(check_pure_function): Use it here.
	(impure_function_callback): New function.
	(resolve_operator): Call it via gfc_expr_walker.

2018-07-18  Janus Weil  <janus@gcc.gnu.org>

	PR fortran/85599
	* gfortran.dg/function_optimize_5.f90: Add option
	'-faggressive-function-elimination' and update dg-warning clauses.
	* gfortran.dg/short_circuiting.f90: New test.

Co-Authored-By: Thomas Koenig <tkoenig@gcc.gnu.org>
From-SVN: r262860