tree-ssa-sccvn.c (get_or_alloc_constant_value_id): Allocate a new entry only if needed.

2010-01-04  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-sccvn.c (get_or_alloc_constant_value_id): Allocate
	a new entry only if needed.
	* tree-ssa-dom.c (lookup_avail_expr): Likewise.
	* tree-ssa-coalesce.c (find_coalesce_pair): Avoid one
	hashtable lookup.
	* tree-ssa-pre.c (sorted_array_from_bitmap_set): Pre-allocate
	the result array.
	(phi_translate): Handle CONSTANTs early.

From-SVN: r155633