[PATCH GCC 5/9]Put copied loop after its preheader and after the original loop's latch in basic block link list

[Bin Cheng]

Hi,
This simple patch changes slpeel_tree_duplicate_loop_edge_cfg by putting copied 
loop after its new preheader and after the original loop's latch in basic 
block's linked list.  It doesn't change CFG at all, but makes the dump cfg a 
little bit easier to read.  I assume this is good for basic block reordering 
too?

Thanks,
bin

2016-09-01  Bin Cheng  <bin.ch...@arm.com>

        * tree-vect-loop-manip.c (slpeel_tree_duplicate_loop_to_edge_cfg): Put
        duplicated loop after its preheader and after the original loop.
diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index 3a3b0bc..b749afa 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -776,7 +776,7 @@ slpeel_tree_duplicate_loop_to_edge_cfg (struct loop *loop,
                                        struct loop *scalar_loop, edge e)
 {
   struct loop *new_loop;
-  basic_block *new_bbs, *bbs;
+  basic_block *new_bbs, *bbs, *pbbs;
   bool at_exit;
   bool was_imm_dom;
   basic_block exit_dest;
@@ -792,12 +792,13 @@ slpeel_tree_duplicate_loop_to_edge_cfg (struct loop *loop,
     scalar_loop = loop;
 
   bbs = XNEWVEC (basic_block, scalar_loop->num_nodes + 1);
-  get_loop_body_with_size (scalar_loop, bbs, scalar_loop->num_nodes);
+  pbbs = bbs + 1;
+  get_loop_body_with_size (scalar_loop, pbbs, scalar_loop->num_nodes);
   /* Allow duplication of outer loops.  */
   if (scalar_loop->inner)
     duplicate_outer_loop = true;
   /* Check whether duplication is possible.  */
-  if (!can_copy_bbs_p (bbs, scalar_loop->num_nodes))
+  if (!can_copy_bbs_p (pbbs, scalar_loop->num_nodes))
     {
       free (bbs);
       return NULL;
@@ -817,15 +818,15 @@ slpeel_tree_duplicate_loop_to_edge_cfg (struct loop *loop,
      pre-header unconditionally for this.  */
   basic_block preheader = split_edge (loop_preheader_edge (scalar_loop));
   edge entry_e = single_pred_edge (preheader);
-  bbs[scalar_loop->num_nodes] = preheader;
+  bbs[0] = preheader;
   new_bbs = XNEWVEC (basic_block, scalar_loop->num_nodes + 1);
 
   exit = single_exit (scalar_loop);
   copy_bbs (bbs, scalar_loop->num_nodes + 1, new_bbs,
            &exit, 1, &new_exit, NULL,
-           e->src, true);
+           at_exit ? loop->latch : e->src, true);
   exit = single_exit (loop);
-  basic_block new_preheader = new_bbs[scalar_loop->num_nodes];
+  basic_block new_preheader = new_bbs[0];
 
   add_phi_args_after_copy (new_bbs, scalar_loop->num_nodes + 1, NULL);