PR c++/21210

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

diff --git a/gcc/tree-loop-linear.c b/gcc/tree-loop-linear.c
index bf353e5..e0f5bd2 100644 (file)
--- a/gcc/tree-loop-linear.c
+++ b/gcc/tree-loop-linear.c
@@ -178,6 +178,9 @@ try_interchange_loops (lambda_trans_matrix trans,
   unsigned int nb_deps_not_carried_by_i, nb_deps_not_carried_by_j;
   struct data_dependence_relation *ddr;
 
+  if (VEC_length (ddr_p, dependence_relations) == 0)
+    return trans;
+
   /* When there is an unknown relation in the dependence_relations, we
      know that it is no worth looking at this loop nest: give up.  */
   ddr = VEC_index (ddr_p, dependence_relations, 0);
@@ -238,6 +241,7 @@ try_interchange_loops (lambda_trans_matrix trans,
 void
 linear_transform_loops (struct loops *loops)
 {
+  bool modified = false;
   unsigned int i;
   VEC(tree,heap) *oldivs = NULL;
   VEC(tree,heap) *invariants = NULL;
@@ -252,7 +256,6 @@ linear_transform_loops (struct loops *loops)
       lambda_loopnest before, after;
       lambda_trans_matrix trans;
       bool problem = false;
-      bool need_perfect_nest = false;
       /* If it's not a loop nest, we don't want it.
          We also don't handle sibling loops properly, 
          which are loops of the following form:
@@ -316,13 +319,9 @@ linear_transform_loops (struct loops *loops)
          continue;
        }
 
-      if (!perfect_nest_p (loop_nest))
-       need_perfect_nest = true;
+      before = gcc_loopnest_to_lambda_loopnest (loops, loop_nest, &oldivs,
+                                               &invariants);
 
-      before = gcc_loopnest_to_lambda_loopnest (loops,
-                                               loop_nest, &oldivs, 
-                                               &invariants,
-                                               need_perfect_nest);
       if (!before)
        continue;
             
@@ -342,6 +341,7 @@ linear_transform_loops (struct loops *loops)
 
       lambda_loopnest_to_gcc_loopnest (loop_nest, oldivs, invariants,
                                       after, trans);
+      modified = true;
 
       if (dump_file)
        fprintf (dump_file, "Successfully transformed loop.\n");
@@ -353,5 +353,7 @@ linear_transform_loops (struct loops *loops)
   VEC_free (tree, heap, oldivs);
   VEC_free (tree, heap, invariants);
   scev_reset ();
-  rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa_full_phi);
+
+  if (modified)
+    rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa_full_phi);
 }