diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 514cdd549900..89665cfacd50 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2014-10-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/63666
+	* tree-vect-slp.c (vect_get_mask_element): Properly handle
+	accessing out-of-bound elements.
+
 2014-10-29  Alexander Ivchenko  <alexander.ivchenko@intel.com>
 	    Maxim Kuznetsov  <maxim.kuznetsov@intel.com>
 	    Anna Tikhonova  <anna.tikhonova@intel.com>
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 90f5ef4b8da0..84bec9544fec 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -2890,7 +2890,7 @@ vect_get_mask_element (gimple stmt, int first_mask_element, int m,
     }
 
   /* The mask requires the next vector.  */
-  if (*current_mask_element >= mask_nunits * 2)
+  while (*current_mask_element >= mask_nunits * 2)
     {
       if (*needs_first_vector || *mask_fixed)
         {
@@ -3041,6 +3041,7 @@ vect_transform_slp_perm_load (slp_tree node, vec<tree> dr_chain,
 					  &number_of_mask_fixes, &mask_fixed,
 					  &needs_first_vector))
 		return false;
+	      gcc_assert (current_mask_element < 2 * nunits);
 	      mask[index++] = current_mask_element;
 
               if (index == nunits)