re PR tree-optimization/17766 (cc1 hangs in with -O3, works with -O2)

re PR tree-optimization/17766 (cc1 hangs in with -O3, works with -O2)

	PR tree-optimization/17766
	* basic-block.h (enum dom_state): DOM_CONS_OK removed.
	(dom_info_available_p): Declare.
	* cfghooks.c (split_block, make_forwarder_block): Use
	dom_info_available_p.
	* dominance.c (compute_dom_fast_query, calculate_dominance_info,
	free_dominance_info, verify_dominators): Ditto.
	(dom_info_available_p): New function.
	* tree-cfg.c (cleanup_control_expr_graph): Free dominance information.
	(thread_jumps): Use dom_info_available_p.
	* tree-complex.c (expand_complex_div_wide): Ditto.
	* tree-mudflap.c (mf_build_check_statement_for): Ditto.

From-SVN: r89147