Ensure that dump calls are guarded with dump_enabled_p

Ensure that dump calls are guarded with dump_enabled_p

If called when !dump_enabled_p, the dump_* functions effectively do
nothing, but as of r263178 this doing "nothing" involves non-trivial
work internally.

I wasn't sure whether the dump_* functions should assert that
  dump_enabled_p ()
is true when they're called, or if they should bail out immediately
for this case, so in this patch I implemented both, so that we get
an assertion failure, and otherwise bail out for the case where
!dump_enabled_p when assertions are disabled.

The patch also fixes all of the places I found during testing
(on x86_64-pc-linux-gnu) that call into dump_* but which
weren't guarded by
  if (dump_enabled_p ())

gcc/ChangeLog:
	* dumpfile.c (VERIFY_DUMP_ENABLED_P): New macro.
	(dump_gimple_stmt): Use it.
	(dump_gimple_stmt_loc): Likewise.
	(dump_gimple_expr): Likewise.
	(dump_gimple_expr_loc): Likewise.
	(dump_generic_expr): Likewise.
	(dump_generic_expr_loc): Likewise.
	(dump_printf): Likewise.
	(dump_printf_loc): Likewise.
	(dump_dec): Likewise.
	(dump_dec): Likewise.
	(dump_hex): Likewise.
	(dump_symtab_node): Likewise.

gcc/ChangeLog:
	* gimple-loop-interchange.cc (tree_loop_interchange::interchange):
	Guard dump call with dump_enabled_p.
	* graphite-isl-ast-to-gimple.c (graphite_regenerate_ast_isl): Likewise.
	* graphite-optimize-isl.c (optimize_isl): Likewise.
	* graphite.c (graphite_transform_loops): Likewise.
	* tree-loop-distribution.c (pass_loop_distribution::execute): Likewise.
	* tree-parloops.c (parallelize_loops): Likewise.
	* tree-ssa-loop-niter.c (number_of_iterations_exit): Likewise.
	* tree-vect-data-refs.c (vect_analyze_group_access_1): Likewise.
	(vect_prune_runtime_alias_test_list): Likewise.
	* tree-vect-loop.c (vect_update_vf_for_slp): Likewise.
	(vect_estimate_min_profitable_iters): Likewise.
	* tree-vect-slp.c (vect_record_max_nunits): Likewise.
	(vect_build_slp_tree_2): Likewise.
	(vect_supported_load_permutation_p): Likewise.
	(vect_slp_analyze_operations): Likewise.
	(vect_slp_analyze_bb_1): Likewise.
	(vect_slp_bb): Likewise.
	* tree-vect-stmts.c (vect_analyze_stmt): Likewise.
	* tree-vectorizer.c (try_vectorize_loop_1): Likewise.
	(pass_slp_vectorize::execute): Likewise.
	(increase_alignment): Likewise.

From-SVN: r266080