Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c	2014-04-28 16:30:59.939239843 +0100
+++ gcc/builtins.c	2014-04-28 16:31:00.252238996 +0100
@@ -8080,6 +8080,7 @@ fold_builtin_bitop (tree fndecl, tree ar
   /* Optimize for constant argument.  */
   if (TREE_CODE (arg) == INTEGER_CST && !TREE_OVERFLOW (arg))
     {
+      tree type = TREE_TYPE (arg);
       int result;
 
       switch (DECL_FUNCTION_CODE (fndecl))
@@ -8089,11 +8090,17 @@ fold_builtin_bitop (tree fndecl, tree ar
 	  break;
 
 	CASE_INT_FN (BUILT_IN_CLZ):
-	  result = wi::clz (arg);
+	  if (wi::ne_p (arg, 0))
+	    result = wi::clz (arg);
+	  else if (! CLZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (type), result))
+	    result = TYPE_PRECISION (type);
 	  break;
 
 	CASE_INT_FN (BUILT_IN_CTZ):
-	  result = wi::ctz (arg);
+	  if (wi::ne_p (arg, 0))
+	    result = wi::ctz (arg);
+	  else if (! CTZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (type), result))
+	    result = TYPE_PRECISION (type);
 	  break;
 
 	CASE_INT_FN (BUILT_IN_CLRSB):
Index: gcc/simplify-rtx.c
===================================================================
--- gcc/simplify-rtx.c	2014-04-28 16:30:59.941239838 +0100
+++ gcc/simplify-rtx.c	2014-04-28 16:31:00.254238990 +0100
@@ -1656,6 +1656,7 @@ simplify_const_unary_operation (enum rtx
       wide_int result;
       enum machine_mode imode = op_mode == VOIDmode ? mode : op_mode;
       rtx_mode_t op0 = std::make_pair (op, imode);
+      int int_value;
 
 #if TARGET_SUPPORTS_WIDE_INT == 0
       /* This assert keeps the simplification from producing a result
@@ -1686,7 +1687,11 @@ simplify_const_unary_operation (enum rtx
 	  break;
 
 	case CLZ:
-	  result = wi::shwi (wi::clz (op0), mode);
+	  if (wi::ne_p (op0, 0))
+	    int_value = wi::clz (op0);
+	  else if (! CLZ_DEFINED_VALUE_AT_ZERO (mode, int_value))
+	    int_value = GET_MODE_PRECISION (mode);
+	  result = wi::shwi (int_value, mode);
 	  break;
 
 	case CLRSB:
@@ -1694,7 +1699,11 @@ simplify_const_unary_operation (enum rtx
 	  break;
 
 	case CTZ:
-	  result = wi::shwi (wi::ctz (op0), mode);
+	  if (wi::ne_p (op0, 0))
+	    int_value = wi::ctz (op0);
+	  else if (! CTZ_DEFINED_VALUE_AT_ZERO (mode, int_value))
+	    int_value = GET_MODE_PRECISION (mode);
+	  result = wi::shwi (int_value, mode);
 	  break;
 
 	case POPCOUNT:
Index: gcc/wide-int.cc
===================================================================
--- gcc/wide-int.cc	2014-04-28 16:30:59.941239838 +0100
+++ gcc/wide-int.cc	2014-04-28 16:31:00.254238990 +0100
@@ -1137,46 +1137,6 @@ wi::add_large (HOST_WIDE_INT *val, const
   return canonize (val, len, prec);
 }
 
-/* This is bogus.  We should always return the precision and leave the
-   caller to handle target dependencies.  */
-static int
-clz_zero (unsigned int precision)
-{
-  unsigned int count;
-
-  enum machine_mode mode = mode_for_size (precision, MODE_INT, 0);
-  if (mode == BLKmode)
-    mode_for_size (precision, MODE_PARTIAL_INT, 0);
-
-  /* Even if the value at zero is undefined, we have to come up
-     with some replacement.  Seems good enough.  */
-  if (mode == BLKmode)
-    count = precision;
-  else if (!CLZ_DEFINED_VALUE_AT_ZERO (mode, count))
-    count = precision;
-  return count;
-}
-
-/* This is bogus.  We should always return the precision and leave the
-   caller to handle target dependencies.  */
-static int
-ctz_zero (unsigned int precision)
-{
-  unsigned int count;
-
-  enum machine_mode mode = mode_for_size (precision, MODE_INT, 0);
-  if (mode == BLKmode)
-    mode_for_size (precision, MODE_PARTIAL_INT, 0);
-
-  /* Even if the value at zero is undefined, we have to come up
-     with some replacement.  Seems good enough.  */
-  if (mode == BLKmode)
-    count = precision;
-  else if (!CTZ_DEFINED_VALUE_AT_ZERO (mode, count))
-    count = precision;
-  return count;
-}
-
 /* Subroutines of the multiplication and division operations.  Unpack
    the first IN_LEN HOST_WIDE_INTs in INPUT into 2 * IN_LEN
    HOST_HALF_WIDE_INTs of RESULT.  The rest of RESULT is filled by
@@ -2002,10 +1962,6 @@ wi::clz (const wide_int_ref &x)
     /* The upper bit is set, so there are no leading zeros.  */
     return 0;
 
-  /* Check whether the value is zero.  */
-  if (high == 0 && x.len == 1)
-    return clz_zero (x.precision);
-
   /* We don't need to look below HIGH.  Either HIGH is nonzero,
      or the top bit of the block below is nonzero; clz_hwi is
      HOST_BITS_PER_WIDE_INT in the latter case.  */
@@ -2047,7 +2003,7 @@ int
 wi::ctz (const wide_int_ref &x)
 {
   if (x.len == 1 && x.ulow () == 0)
-    return ctz_zero (x.precision);
+    return x.precision;
 
   /* Having dealt with the zero case, there must be a block with a
      nonzero bit.  We don't care about the bits above the first 1.  */
