tree-ssa-loop-prefetch.c (prune_ref_by_group_reuse): Reset prefetch_before to…

tree-ssa-loop-prefetch.c (prune_ref_by_group_reuse): Reset prefetch_before to PREFETCH_ALL if to accesses "meet" beyond cache size.

2010-05-11  Christian Borntraeger  <borntraeger@de.ibm.com>

        * tree-ssa-loop-prefetch.c (prune_ref_by_group_reuse): Reset
	prefetch_before to PREFETCH_ALL if to accesses "meet" beyond
	cache size.

From-SVN: r159257

gcc/ChangeLog

 2010-05-11  Christian Borntraeger  <borntraeger@de.ibm.com>
 
+        * tree-ssa-loop-prefetch.c (prune_ref_by_group_reuse): Reset
+	prefetch_before to PREFETCH_ALL if to accesses "meet" beyond
+	cache size.
+
+2010-05-11  Christian Borntraeger  <borntraeger@de.ibm.com>
+
         * tree-ssa-loop-prefetch.c: Add debug for dropped prefetches.
 
 2010-05-11  Jakub Jelinek  <jakub@redhat.com>

gcc/tree-ssa-loop-prefetch.c

@@ -716,6 +716,9 @@ prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by,
       hit_from = ddown (delta_b, PREFETCH_BLOCK) * PREFETCH_BLOCK;
       prefetch_before = (hit_from - delta_r + step - 1) / step;
 
+      /* Do not reduce prefetch_before if we meet beyond cache size.  */
+      if (prefetch_before > abs (L2_CACHE_SIZE_BYTES / step))
+        prefetch_before = PREFETCH_ALL;
       if (prefetch_before < ref->prefetch_before)
 	ref->prefetch_before = prefetch_before;
 
@@ -746,6 +749,9 @@ prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by,
 				reduced_prefetch_block, align_unit);
   if (miss_rate <= ACCEPTABLE_MISS_RATE)
     {
+      /* Do not reduce prefetch_before if we meet beyond cache size.  */
+      if (prefetch_before > L2_CACHE_SIZE_BYTES / PREFETCH_BLOCK)
+        prefetch_before = PREFETCH_ALL;
       if (prefetch_before < ref->prefetch_before)
 	ref->prefetch_before = prefetch_before;