Update dom_info

Update dom_info

2016-10-17  Yuri Rumyantsev  <ysrumyan@gmail.com>

	* dominance.c (dom_info::dom_info): Add new constructor for region
	which is vector of basic blocks.
	(dom_init): New method to initialize members common for both
	constructors.
	(dom_info::dom_info): Invoke dom_init for partial initialization.
	(dom_info::get_idom): Add check to corner cases on basic blocks which
	are not in region.
	(dom_info::calc_dfs_tree): Check M_FAKE_EXIT_EDGE instead of M_REVERSE
	to detect unreachable bbs.
	(dom_info::calc_idoms): Likewise.
	(compute_dom_fast_query_in_region): New function.
	(calculate_dominance_info_for_region): Likewise.
	(free_dominance_info_for_region): Likewise.
	* dominance.h: Add prototypes for introduced region-based functions
	tree-if-conv.c: (build_region): New function.
	(if_convertible_loop_p_1): Invoke local version of post-dominators
	calculation before basic block predication with subsequent freeing
	post-dominator info.
	(tree_if_conversion): Remove free of post-dominator info
	(pass_if_conversion::execute): Delete detection of infinite loops
	and fake edges to exit block since post-dominator calculation is
	performed per if-converted loop only.

From-SVN: r241275