diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 99021a82df4..bc8ba4607a5 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -10541,15 +10541,24 @@ fold_vec_perm (tree type, tree arg0, tree arg1, const vec_perm_indices &sel)
   unsigned HOST_WIDE_INT nelts;
   bool need_ctor = false;
 
-  if (!sel.length ().is_constant (&nelts))
-    return NULL_TREE;
-  gcc_assert (known_eq (TYPE_VECTOR_SUBPARTS (type), nelts)
-	      && known_eq (TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg0)), nelts)
-	      && known_eq (TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg1)), nelts));
+  gcc_assert (known_eq (TYPE_VECTOR_SUBPARTS (type),
+			sel.length ()));
+  gcc_assert (known_eq (TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg0)),
+			TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg1))));
+
   if (TREE_TYPE (TREE_TYPE (arg0)) != TREE_TYPE (type)
       || TREE_TYPE (TREE_TYPE (arg1)) != TREE_TYPE (type))
     return NULL_TREE;
 
+  /* TODO: Handle VEC_PERM_EXPR with differing lengths.  */
+  if (!known_eq (TYPE_VECTOR_SUBPARTS (type),
+		 TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg0))))
+    return NULL_TREE;
+
+  /* TODO: Handle VLA vectors.  */
+  if (!sel.length ().is_constant (&nelts))
+    return NULL_TREE;
+
   tree *in_elts = XALLOCAVEC (tree, nelts * 2);
   if (!vec_cst_ctor_to_array (arg0, nelts, in_elts)
       || !vec_cst_ctor_to_array (arg1, nelts, in_elts + nelts))
diff --git a/gcc/match.pd b/gcc/match.pd
index 330c1db0c8e..aa20cc713c5 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -7845,6 +7845,12 @@ and,
  (with
   {
     tree op0 = @0, op1 = @1, op2 = @2;
+
+    gcc_assert (known_eq (TYPE_VECTOR_SUBPARTS (type),
+			  TYPE_VECTOR_SUBPARTS (TREE_TYPE (op2))));
+    gcc_assert (known_eq (TYPE_VECTOR_SUBPARTS (TREE_TYPE (op0)),
+			  TYPE_VECTOR_SUBPARTS (TREE_TYPE (op1))));
+
     machine_mode result_mode = TYPE_MODE (type);
     machine_mode op_mode = TYPE_MODE (TREE_TYPE (op0));
 
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index fdc4bc8909d..4b693ef095c 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -2661,7 +2661,9 @@ simplify_permutation (gimple_stmt_iterator *gsi)
 
       /* Shuffle of a constructor.  */
       bool ret = false;
-      tree res_type = TREE_TYPE (arg0);
+      tree res_type
+	= build_vector_type (TREE_TYPE (TREE_TYPE (arg0)),
+			     TYPE_VECTOR_SUBPARTS (TREE_TYPE (op2)));
       tree opt = fold_ternary (VEC_PERM_EXPR, res_type, arg0, arg1, op2);
       if (!opt
 	  || (TREE_CODE (opt) != CONSTRUCTOR && TREE_CODE (opt) != VECTOR_CST))