diff --git a/lib/clz_ctz.c b/lib/clz_ctz.c
index a8f8379..2e11e48 100644
--- a/lib/clz_ctz.c
+++ b/lib/clz_ctz.c
@@ -6,6 +6,9 @@
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
+ * The functions in this file aren't called directly, but are required by
+ * GCC builtins such as __builtin_ctz, and therefore they can't be removed
+ * despite appearing unreferenced in kernel source.
  *
  * __c[lt]z[sd]i2 can be overridden by linking arch-specific versions.
  */
@@ -13,18 +16,22 @@
 #include <linux/export.h>
 #include <linux/kernel.h>
 
+int __weak __ctzsi2(int val);
 int __weak __ctzsi2(int val)
 {
 	return __ffs(val);
 }
 EXPORT_SYMBOL(__ctzsi2);
 
+int __weak __clzsi2(int val);
 int __weak __clzsi2(int val)
 {
 	return 32 - fls(val);
 }
 EXPORT_SYMBOL(__clzsi2);
 
+int __weak __clzdi2(long val);
+int __weak __ctzdi2(long val);
 #if BITS_PER_LONG == 32
 
 int __weak __clzdi2(long val)