--- a/gcc/tree-iterator.c	Sun Aug 21 07:07:55 2011 +0900
+++ b/gcc/tree-iterator.c	Fri Oct 27 22:46:09 2017 +0900
@@ -1,6 +1,5 @@
 /* Iterator routines for manipulating GENERIC and GIMPLE tree statements.
-   Copyright (C) 2003, 2004, 2007, 2008, 2009, 2010
-   Free Software Foundation, Inc.
+   Copyright (C) 2003-2017 Free Software Foundation, Inc.
    Contributed by Andrew MacLeod  <amacleod@redhat.com>
 
 This file is part of GCC.
@@ -23,25 +22,22 @@
 #include "system.h"
 #include "coretypes.h"
 #include "tree.h"
-#include "gimple.h"
 #include "tree-iterator.h"
-#include "ggc.h"
 
 
 /* This is a cache of STATEMENT_LIST nodes.  We create and destroy them
    fairly often during gimplification.  */
 
-static GTY ((deletable (""))) tree stmt_list_cache;
+static GTY ((deletable (""))) vec<tree, va_gc> *stmt_list_cache;
 
 tree
 alloc_stmt_list (void)
 {
-  tree list = stmt_list_cache;
-  if (list)
+  tree list;
+  if (!vec_safe_is_empty (stmt_list_cache))
     {
-      stmt_list_cache = TREE_CHAIN (list);
-      gcc_assert (stmt_list_cache != list);
-      memset (list, 0, sizeof(struct tree_common));
+      list = stmt_list_cache->pop ();
+      memset (list, 0, sizeof (struct tree_base));
       TREE_SET_CODE (list, STATEMENT_LIST);
     }
   else
@@ -55,11 +51,7 @@
 {
   gcc_assert (!STATEMENT_LIST_HEAD (t));
   gcc_assert (!STATEMENT_LIST_TAIL (t));
-  /* If this triggers, it's a sign that the same list is being freed
-     twice.  */
-  gcc_assert (t != stmt_list_cache || stmt_list_cache == NULL);
-  TREE_CHAIN (t) = stmt_list_cache;
-  stmt_list_cache = t;
+  vec_safe_push (stmt_list_cache, t);
 }
 
 /* A subroutine of append_to_statement_list{,_force}.  T is not NULL.  */
@@ -79,6 +71,13 @@
 	}
       *list_p = list = alloc_stmt_list ();
     }
+  else if (TREE_CODE (list) != STATEMENT_LIST)
+    {
+      tree first = list;
+      *list_p = list = alloc_stmt_list ();
+      i = tsi_last (list);
+      tsi_link_after (&i, first, TSI_CONTINUE_LINKING);
+    }
 
   i = tsi_last (list);
   tsi_link_after (&i, t, TSI_CONTINUE_LINKING);
@@ -131,7 +130,7 @@
     }
   else
     {
-      head = ggc_alloc_tree_statement_list_node ();
+      head = ggc_alloc<tree_statement_list_node> ();
       head->prev = NULL;
       head->next = NULL;
       head->stmt = t;
@@ -207,7 +206,7 @@
     }
   else
     {
-      head = ggc_alloc_tree_statement_list_node ();
+      head = ggc_alloc<tree_statement_list_node> ();
       head->prev = NULL;
       head->next = NULL;
       head->stmt = t;