* tree-ssa-dom.c (block_defs_stack): Remove, no longer needed.
	(restore_currdefs_to_original_value): Likewise.
	(register_definitions_for_stmt): Likewise.
	(tree_ssa_dominator_optimize): No longer initialize CURRENT_DEF
	for each variable.  Do not allocate/free block_defs_stack either.
	Do not iterate if we just thread jumps.  Only iterate if the
	tree_cleanup_cfg does useful work (temporary).
	(dom_opt_initialize_block): No longer push a marker on
	BLOCK_DEFS_STACK.
	(dom_opt_finalize_block): Removal call to restore currdefs.
	Relax restrictions for recording edge equivalences.
	(record_equivalences_from_phis): No longer need to track
	CURRENT_DEF.
	(optimize_stmt): Similarly.
	(thread_across_edge): Simplify by removing the requirement that
	statements in the block we are threading through must be nops.
	(initialize_hash_element): Handle GOTO_EXPR.

From-SVN: r98597