2010-05-07  Changpeng Fang  <changpeng.fang@amd.com>

	* tree-ssa-loop-prefetch.c (TRIP_COUNT_TO_AHEAD_RATIO): New.
	(is_loop_prefetching_profitable): Do not insert prefetches
	when the trip count is not at least TRIP_COUNT_TO_AHEAD_RATIO
	times the prefetch ahead distance.

From-SVN: r159163