2008-03-17 Jerry DeLisle <jvdelisle@gcc.gnu.org>

[pf3gnuchains/gcc-fork.git] / gcc / tree-loop-linear.c

diff --git a/gcc/tree-loop-linear.c b/gcc/tree-loop-linear.c
index 88a77dd..806d9e6 100644 (file)
--- a/gcc/tree-loop-linear.c
+++ b/gcc/tree-loop-linear.c
@@ -179,10 +179,14 @@ try_interchange_loops (lambda_trans_matrix trans,
                       VEC (data_reference_p, heap) *datarefs,
                       struct loop *first_loop)
 {
+  bool res;
   struct loop *loop_i;
   struct loop *loop_j;
   unsigned int dependence_steps_i, dependence_steps_j;
   double_int access_strides_i, access_strides_j;
+  double_int small, large, nb_iter;
+  double_int l1_cache_size, l2_cache_size;
+  int cmp;
   unsigned int nb_deps_not_carried_by_i, nb_deps_not_carried_by_j;
   struct data_dependence_relation *ddr;
 
@@ -194,7 +198,10 @@ try_interchange_loops (lambda_trans_matrix trans,
   ddr = VEC_index (ddr_p, dependence_relations, 0);
   if (ddr == NULL || DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
     return trans;
-  
+
+  l1_cache_size = uhwi_to_double_int (L1_CACHE_SIZE * 1024);
+  l2_cache_size = uhwi_to_double_int (L2_CACHE_SIZE * 1024);
+
   /* LOOP_I is always the outer loop.  */
   for (loop_j = first_loop->inner; 
        loop_j; 
@@ -216,18 +223,38 @@ try_interchange_loops (lambda_trans_matrix trans,
        
        /* Heuristics for loop interchange profitability:
 
+          0. Don't transform if the smallest stride is larger than
+             the L2 cache, or if the largest stride multiplied by the
+             number of iterations is smaller than the L1 cache.
+
           1. (spatial locality) Inner loops should have smallest
               dependence steps.
 
           2. (spatial locality) Inner loops should contain more
           dependence relations not carried by the loop.
 
-          3. (temporal locality) Inner loops should have smallest 
+          3. (temporal locality) Inner loops should have smallest
              array access strides.
        */
+
+       cmp = double_int_ucmp (access_strides_i, access_strides_j);
+       small = cmp < 0 ? access_strides_i : access_strides_j;
+       large = cmp < 0 ? access_strides_j : access_strides_i;
+
+       if (double_int_ucmp (small, l2_cache_size) > 0)
+         continue;
+
+       res = cmp < 0 ?
+         estimated_loop_iterations (loop_j, false, &nb_iter):
+         estimated_loop_iterations (loop_i, false, &nb_iter);
+       large = double_int_mul (large, nb_iter);
+
+       if (res && double_int_ucmp (large, l1_cache_size) < 0)
+         continue;
+
        if (dependence_steps_i < dependence_steps_j 
            || nb_deps_not_carried_by_i > nb_deps_not_carried_by_j
-           || double_int_ucmp (access_strides_i, access_strides_j) < 0)
+           || cmp < 0)
          {
            lambda_matrix_row_exchange (LTM_MATRIX (trans),
                                        loop_depth (loop_i) - loop_depth (first_loop),