diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 52ec9bdd35c..ddd35cd3be7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,9 +1,16 @@
+2007-01-29  Roger Sayle  <roger@eyesopen.com>
+	    Richard Guenther  <rguenther@suse.de>
+
+	* fold-const.c (round_up): Make HIGH an unsigned HOST_WIDE_INT to
+	avoid undefined behaviour on overflow.  Use force_fit_type_double
+	to construct the constant with the specified TREE_OVERFLOW.
+
 2007-01-29  Janis Johnson  <janis187@us.ibm.com>
 
 	* config/dfp-bit.c: Add parameterized support for fp exceptions.
 	* config/dfp-bit.h: Ditto.
 
-007-01-29  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>
+2007-01-29  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>
 
 	* c-decl.c (pop_scope): Replace warnings with call to
 	warn_for_unused_label.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index a7a12eb1d92..e0cab9cb889 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -13514,33 +13514,33 @@ round_up (tree value, int divisor)
   /* If divisor is a power of two, simplify this to bit manipulation.  */
   if (divisor == (divisor & -divisor))
     {
-      tree t;
-
       if (TREE_CODE (value) == INTEGER_CST)
 	{
 	  unsigned HOST_WIDE_INT low = TREE_INT_CST_LOW (value);
-	  HOST_WIDE_INT high;
+	  unsigned HOST_WIDE_INT high;
+	  bool overflow_p;
 
 	  if ((low & (divisor - 1)) == 0)
 	    return value;
 
+	  overflow_p = TREE_OVERFLOW (value);
 	  high = TREE_INT_CST_HIGH (value);
 	  low &= ~(divisor - 1);
 	  low += divisor;
 	  if (low == 0)
-	    high++;
-
-	  t = build_int_cst_wide_type (TREE_TYPE (value), low, high);
-	  if ((TREE_OVERFLOW (value) || integer_zerop (t))
-	      && !TREE_OVERFLOW (t))
 	    {
-	      t = copy_node (t);
-	      TREE_OVERFLOW (t) = 1;
+	      high++;
+	      if (high == 0)
+		overflow_p = true;
 	    }
-	  return t;
+
+	  return force_fit_type_double (TREE_TYPE (value), low, high,
+					-1, overflow_p);
 	}
       else
 	{
+	  tree t;
+
 	  t = build_int_cst (TREE_TYPE (value), divisor - 1);
 	  value = size_binop (PLUS_EXPR, value, t);
 	  t = build_int_cst (TREE_TYPE (value), -divisor);