re PR tree-optimization/64058 (Performance degradation after r216304)

re PR tree-optimization/64058 (Performance degradation after r216304)

	PR tree-optimization/64058
	* tree-ssa-coalesce.c (struct coalesce_pair): Add new field
	CONFLICT_COUNT.
	(struct ssa_conflicts): Move up earlier in the file.
	(conflicts_, var_map_): New static variables.
	(initialize_conflict_count): New function to initialize the
	CONFLICT_COUNT field for each conflict pair.
	(compare_pairs): Lazily initialize the conflict count and use it
	as the first tie-breaker.
	(sort_coalesce_list): Add new arguments conflicts, map.  Initialize
	and wipe conflicts_ and map_ around the call to qsort.  Remove
	special case for 2 coalesce pairs.
	* bitmap.c (bitmap_count_unique_bits): New function.
	(bitmap_count_bits_in_word): New function, extracted from
	bitmap_count_bits.
	(bitmap_count_bits): Use bitmap_count_bits_in_word.
	* bitmap.h (bitmap_count_unique_bits): Declare it.

From-SVN: r234425