* tree-ssanames.c (make_ssa_name): No longer need to clear, then
	initialize key elements here.
	(release_ssa_name): Zero the released SSA_NAME here.
	* tree.h (SSA_NAME_EQUIV, SET_SSA_NAME_EQUIV): New macros.
	(struct tree_ssa_name): Add new "equiv" field.
	* tree-ssa-dom.c (const_and_copies): Kill the global varray.
	(tree_ssa_dominator_optimize): No longer allocate, resize or
	clear CONST_AND_COPIES.
	(get_value_for, set_value_for): Kill.
	(thread_across_edge): Get/set the equivalency using
	SSA_NAME_EQUIV and SET_SSA_NAME_EQUIV.
	(restore_vars_to_original_value): Likewise.
	(record_equivalences_from_phis): Likewise.
	(record_dominating_conditions): Likewise.
	(record_const_or_copy, record_equality): Likewise.
	(lookup_avail_expr): Likewise.
	(record_equivalences_from_stmt, cprop_operand): Likewise.
	(cprop_into_successor_phis): No longer need to pass around
	CONST_AND_COPIES.  Callers updated. Get equivalences via
	SSA_NAME_EQUIV.
	(cprop_into_phis): Likewise.

Co-Authored-By: Jan Hubicka <jh@suse.cz>

From-SVN: r87787