+# LC_INTERVAL_TREE_CACHED
+#
+# 4.14 f808c13fd3738948e10196496959871130612b61
+# switched INTERVAL_TREE_DEFINE to use cached RB_Trees.
+#
+AC_DEFUN([LC_INTERVAL_TREE_CACHED], [
+tmp_flags="$EXTRA_KCFLAGS"
+EXTRA_KCFLAGS="-Werror"
+LB_CHECK_COMPILE([if interval_trees use rb_tree_cached],
+itree_cached, [
+ #include <linux/interval_tree_generic.h>
+ struct foo { struct rb_node rb; int last; int a,b;};
+ #define START(n) ((n)->a)
+ #define LAST(n) ((n)->b)
+ struct rb_root_cached tree;
+ INTERVAL_TREE_DEFINE(struct foo, rb, int, last,
+ START, LAST, , foo);
+],[
+ foo_insert(NULL, &tree);
+],[
+ AC_DEFINE(HAVE_INTERVAL_TREE_CACHED, 1,
+ [interval trees use rb_tree_cached])
+])
+EXTRA_KCFLAGS="$tmp_flags"
+]) # LC_INTERVAL_TREE_CACHED
+
+#