diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 11b1938216e..d10a276daf2 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -52,6 +52,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-ssa-dce.h"
 #include "tree-cfgcleanup.h"
 #include "alias.h"
+#include "graph.h"
 
 /* Even though this file is called tree-ssa-pre.c, we actually
    implement a bit more than just PRE here.  All of them piggy-back
@@ -500,7 +501,6 @@ typedef struct bb_bitmap_sets
 #define BB_MAY_NOTRETURN(BB) ((bb_value_sets_t) ((BB)->aux))->contains_may_not_return_call
 #define BB_LIVE_VOP_ON_EXIT(BB) ((bb_value_sets_t) ((BB)->aux))->vop_on_exit
 
-
 /* This structure is used to keep track of statistics on what
    optimization PRE was able to perform.  */
 static struct
@@ -2434,6 +2434,25 @@ compute_antic (void)
    that didn't turn out to be necessary.   */
 static bitmap inserted_exprs;
 
+struct pre_expr_block_d : nofree_ptr_hash <pre_expr_block_d>
+{
+  pre_expr expr;
+  bitmap blocks;
+
+  /* hash_table support.  */
+  static inline hashval_t hash(const pre_expr_block_d *x)
+  {
+    return pre_expr_d::hash (x->expr);
+  }
+
+  static inline int equal(const pre_expr_block_d *x1, const pre_expr_block_d *x2)
+  {
+    return pre_expr_d::equal (x1->expr, x2->expr);
+  }
+};
+
+static hash_table<pre_expr_block_d> * expr_to_blocks;
+
 /* The actual worker for create_component_ref_by_pieces.  */
 
 static tree
@@ -3549,6 +3568,15 @@ do_hoist_insertion (basic_block block)
 	  continue;
 	}
 
+      pre_expr_block_d x;
+      x.expr = expr;
+      pre_expr_block_d **slot = expr_to_blocks->find_slot (&x, NO_INSERT);
+      if (slot)
+	{
+	  gcc_assert (!bitmap_empty_p ((*slot)->blocks));
+	  continue;
+	}
+
       /* OK, we should hoist this value.  Perform the transformation.  */
       pre_stats.hoist_insert++;
       if (dump_file && (dump_flags & TDF_DETAILS))
@@ -3678,6 +3706,40 @@ insert (void)
   statistics_histogram_event (cfun, "insert iterations", num_iterations);
 }
 
+static void
+add_expr_to_blocks (pre_expr expr, basic_block block)
+{
+  pre_expr_block_d x;
+  x.expr = expr;
+
+  edge e;
+  edge_iterator ei;
+  bool loop_exit = false;
+
+  if (single_succ_p (block))
+    return;
+
+  FOR_EACH_EDGE (e, ei, block->succs)
+    if (block->loop_father != e->dest->loop_father)
+      {
+	loop_exit = true;
+	break;
+      }
+
+  if (!loop_exit)
+    return;
+
+  pre_expr_block_d **slot = expr_to_blocks->find_slot (&x, INSERT);
+  if (!*slot)
+    {
+      *slot = XNEW (struct pre_expr_block_d);
+      (*slot)->expr = expr;
+      (*slot)->blocks = BITMAP_ALLOC (NULL);
+    }
+
+   
+  bitmap_set_bit ((*slot)->blocks, block->index);
+}
 
 /* Compute the AVAIL set for all basic blocks.
 
@@ -3711,6 +3773,7 @@ compute_avail (void)
 
       e = get_or_alloc_expr_for_name (name);
       add_to_value (get_expr_value_id (e), e);
+      add_expr_to_blocks (e, ENTRY_BLOCK_PTR_FOR_FN (cfun));
       bitmap_insert_into_set (TMP_GEN (ENTRY_BLOCK_PTR_FOR_FN (cfun)), e);
       bitmap_value_insert_into_set (AVAIL_OUT (ENTRY_BLOCK_PTR_FOR_FN (cfun)),
 				    e);
@@ -3771,6 +3834,7 @@ compute_avail (void)
 
 	  pre_expr e = get_or_alloc_expr_for_name (result);
 	  add_to_value (get_expr_value_id (e), e);
+	  add_expr_to_blocks (e, block);
 	  bitmap_value_insert_into_set (AVAIL_OUT (block), e);
 	  bitmap_insert_into_set (PHI_GEN (block), e);
 	}
@@ -3808,6 +3872,7 @@ compute_avail (void)
 	      pre_expr e = get_or_alloc_expr_for_name (op);
 
 	      add_to_value (get_expr_value_id (e), e);
+	      add_expr_to_blocks (e, block);
 	      bitmap_insert_into_set (TMP_GEN (block), e);
 	      bitmap_value_insert_into_set (AVAIL_OUT (block), e);
 	    }
@@ -3862,6 +3927,7 @@ compute_avail (void)
 		    PRE_EXPR_REFERENCE (result) = ref;
 
 		    get_or_alloc_expression_id (result);
+		    add_expr_to_blocks (result, block);
 		    add_to_value (get_expr_value_id (result), result);
 		    bitmap_value_insert_into_set (EXP_GEN (block), result);
 		  }
@@ -4019,6 +4085,7 @@ compute_avail (void)
 
 		get_or_alloc_expression_id (result);
 		add_to_value (get_expr_value_id (result), result);
+		add_expr_to_blocks (result, block);
 		bitmap_value_insert_into_set (EXP_GEN (block), result);
 		continue;
 	      }
@@ -4077,6 +4144,7 @@ init_pre (void)
   bitmap_obstack_initialize (&grand_bitmap_obstack);
   phi_translate_table = new hash_table<expr_pred_trans_d> (5110);
   expression_to_id = new hash_table<pre_expr_d> (num_ssa_names * 3);
+  expr_to_blocks = new hash_table<pre_expr_block_d> (num_ssa_names * 3);
   FOR_ALL_BB_FN (bb, cfun)
     {
       EXP_GEN (bb) = bitmap_set_new ();