PR c++/49092

[pf3gnuchains/gcc-fork.git] / gcc / cfgloopmanip.c

diff --git a/gcc/cfgloopmanip.c b/gcc/cfgloopmanip.c
index aa9ab66..1824421 100644 (file)
--- a/gcc/cfgloopmanip.c
+++ b/gcc/cfgloopmanip.c
@@ -1,5 +1,5 @@
 /* Loop manipulation code for GNU compiler.
-   Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
+   Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
    Free Software Foundation, Inc.
 
 This file is part of GCC.
@@ -174,7 +174,7 @@ fix_bb_placements (basic_block from,
 {
   sbitmap in_queue;
   basic_block *queue, *qtop, *qbeg, *qend;
-  struct loop *base_loop;
+  struct loop *base_loop, *target_loop;
   edge e;
 
   /* We pass through blocks back-reachable from FROM, testing whether some
@@ -185,7 +185,11 @@ fix_bb_placements (basic_block from,
      fix_loop_placement.  */
 
   base_loop = from->loop_father;
-  if (base_loop == current_loops->tree_root)
+  /* If we are already in the outermost loop, the basic blocks cannot be moved
+     outside of it.  If FROM is the header of the base loop, it cannot be moved
+     outside of it, either.  In both cases, we can end now.  */
+  if (base_loop == current_loops->tree_root
+      || from == base_loop->header)
     return;
 
   in_queue = sbitmap_alloc (last_basic_block);
@@ -214,12 +218,14 @@ fix_bb_placements (basic_block from,
          /* Subloop header, maybe move the loop upward.  */
          if (!fix_loop_placement (from->loop_father))
            continue;
+         target_loop = loop_outer (from->loop_father);
        }
       else
        {
          /* Ordinary basic block.  */
          if (!fix_bb_placement (from))
            continue;
+         target_loop = from->loop_father;
        }
 
       FOR_EACH_EDGE (e, ei, from->succs)
@@ -248,9 +254,12 @@ fix_bb_placements (basic_block from,
              && (nca == base_loop
                  || nca != pred->loop_father))
            pred = pred->loop_father->header;
-         else if (!flow_loop_nested_p (from->loop_father, pred->loop_father))
+         else if (!flow_loop_nested_p (target_loop, pred->loop_father))
            {
-             /* No point in processing it.  */
+             /* If PRED is already higher in the loop hierarchy than the
+                TARGET_LOOP to that we moved FROM, the change of the position
+                of FROM does not affect the position of PRED, so there is no
+                point in processing it.  */
              continue;
            }