PR 44576: miss rate computation improvement for prefetching loop arrays.

2010-07-02  Changpeng Fang  <changpeng.fang@amd.com>

	PR middle-end/44576
	* tree-ssa-loop-prefetch.c (compute_miss_rate): Return 1000 (out
	of 1000) for miss rate if the address diference is greater than or
	equal to the cache line size (the two reference will never hit the
	same cache line).

From-SVN: r161727

gcc/ChangeLog

+2010-07-02  Changpeng Fang  <changpeng.fang@amd.com>
+
+	PR middle-end/44576
+	* tree-ssa-loop-prefetch.c (compute_miss_rate): Return 1000 (out
+	of 1000) for miss rate if the address diference is greater than or
+	equal to the cache line size (the two reference will never hit the
+	same cache line).
+
 2010-07-02  Bernd Schmidt  <bernds@codesourcery.com>
 
 	PR target/42835

gcc/tree-ssa-loop-prefetch.c

@@ -654,6 +654,11 @@ compute_miss_rate (unsigned HOST_WIDE_INT cache_line_size,
   int total_positions, miss_positions, miss_rate;
   int address1, address2, cache_line1, cache_line2;
 
+  /* It always misses if delta is greater than or equal to the cache
+     line size.  */
+  if (delta >= cache_line_size)
+    return 1000;
+
   total_positions = 0;
   miss_positions = 0;