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.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@159257 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5b1d3dd..4ade883 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 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>

diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c
index 2fc901d..daf9956 100644 (file)
--- a/gcc/tree-ssa-loop-prefetch.c
+++ b/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;