diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 672e384ef09..9f91878c468 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -4325,10 +4325,11 @@ verify_gimple_assign_ternary (gassign *stmt)
       break;
 
     case VEC_PERM_EXPR:
-      if (!useless_type_conversion_p (lhs_type, rhs1_type)
-	  || !useless_type_conversion_p (lhs_type, rhs2_type))
+      if (TREE_CODE (rhs1_type) != VECTOR_TYPE
+	  || TREE_CODE (rhs2_type) != VECTOR_TYPE
+	  || TREE_CODE (rhs3_type) != VECTOR_TYPE)
 	{
-	  error ("type mismatch in %qs", code_name);
+	  error ("vector types expected in %qs", code_name);
 	  debug_generic_expr (lhs_type);
 	  debug_generic_expr (rhs1_type);
 	  debug_generic_expr (rhs2_type);
@@ -4336,11 +4337,14 @@ verify_gimple_assign_ternary (gassign *stmt)
 	  return true;
 	}
 
-      if (TREE_CODE (rhs1_type) != VECTOR_TYPE
-	  || TREE_CODE (rhs2_type) != VECTOR_TYPE
-	  || TREE_CODE (rhs3_type) != VECTOR_TYPE)
+      if (TREE_CODE (TREE_TYPE (rhs3_type)) != INTEGER_TYPE
+	  || (TREE_CODE (rhs3) != VECTOR_CST
+	      && (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE
+				    (TREE_TYPE (rhs3_type)))
+		  != GET_MODE_BITSIZE (SCALAR_TYPE_MODE
+				       (TREE_TYPE (rhs1_type))))))
 	{
-	  error ("vector types expected in %qs", code_name);
+	  error ("invalid mask type in %qs", code_name);
 	  debug_generic_expr (lhs_type);
 	  debug_generic_expr (rhs1_type);
 	  debug_generic_expr (rhs2_type);
@@ -4348,15 +4352,18 @@ verify_gimple_assign_ternary (gassign *stmt)
 	  return true;
 	}
 
-      if (maybe_ne (TYPE_VECTOR_SUBPARTS (rhs1_type),
-		    TYPE_VECTOR_SUBPARTS (rhs2_type))
-	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs2_type),
-		       TYPE_VECTOR_SUBPARTS (rhs3_type))
-	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs3_type),
-		       TYPE_VECTOR_SUBPARTS (lhs_type)))
+      /* Accept lhs = vec_perm_expr<v, v, mask> if lhs is vector length agnostic,
+	 and has same element type as v.  */
+      if (!TYPE_VECTOR_SUBPARTS (lhs_type).is_constant ()
+	  && operand_equal_p (rhs1, rhs2, 0)
+	  && TYPE_VECTOR_SUBPARTS (rhs1_type).is_constant ()
+	  && TREE_TYPE (lhs_type) == TREE_TYPE (rhs1_type)) 
+	return false;
+
+      if (!useless_type_conversion_p (lhs_type, rhs1_type)
+	  || !useless_type_conversion_p (lhs_type, rhs2_type))
 	{
-	  error ("vectors with different element number found in %qs",
-		 code_name);
+	  error ("type mismatch in %qs", code_name);
 	  debug_generic_expr (lhs_type);
 	  debug_generic_expr (rhs1_type);
 	  debug_generic_expr (rhs2_type);
@@ -4364,21 +4371,21 @@ verify_gimple_assign_ternary (gassign *stmt)
 	  return true;
 	}
 
-      if (TREE_CODE (TREE_TYPE (rhs3_type)) != INTEGER_TYPE
-	  || (TREE_CODE (rhs3) != VECTOR_CST
-	      && (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE
-				    (TREE_TYPE (rhs3_type)))
-		  != GET_MODE_BITSIZE (SCALAR_TYPE_MODE
-				       (TREE_TYPE (rhs1_type))))))
+      if (maybe_ne (TYPE_VECTOR_SUBPARTS (rhs1_type),
+		    TYPE_VECTOR_SUBPARTS (rhs2_type))
+	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs2_type),
+		       TYPE_VECTOR_SUBPARTS (rhs3_type))
+	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs3_type),
+		       TYPE_VECTOR_SUBPARTS (lhs_type)))
 	{
-	  error ("invalid mask type in %qs", code_name);
+	  error ("vectors with different element number found in %qs",
+		 code_name);
 	  debug_generic_expr (lhs_type);
 	  debug_generic_expr (rhs1_type);
 	  debug_generic_expr (rhs2_type);
 	  debug_generic_expr (rhs3_type);
 	  return true;
 	}
-
       return false;
 
     case SAD_EXPR: