* tree-cfg.c (hashtab.h): Include.
	(struct edge_to_case_leader_elt): New structure.
	(edge_to_case_leader): New.
	(edge_to_case_leader_hash): New hashtable hasing function.
	(edge_to_case_leader_eq): New hashtable equality function.
	(record_switch_edge): New function.
	(get_case_leader_for_edge, get_case_leader_for_edge): New functions.
	(make_switch_expr_edges): Build the edge-to-case-leader
	hash table.  Tear down the hash table when we're done.
	(cleanup_dead_labels): Use CASE_LEADER_OR_LABEL instead of
	CASE_LABEL.
	(tree_node_can_be_shared): Allow sharing of CASE_LABEL_EXPR nodes.
	(tree_redirect_edge_and_branch, case SWITCH_EXPR): Update
	to use new concept of case leaders to reduce overhead of
	redirecting outgoing edges from switch statements.
	* tree.c (get_case_label): New function.
	* tree.h (CASE_LABEL): Define in terms of get_case_label.
	(CASE_LEADER_OR_LABEL): Define.

From-SVN: r90570