+#if defined (__aarch64__)
+
+#if W_TYPE_SIZE == 32
+#define count_leading_zeros(COUNT, X) ((COUNT) = __builtin_clz (X))
+#define count_trailing_zeros(COUNT, X) ((COUNT) = __builtin_ctz (X))
+#define COUNT_LEADING_ZEROS_0 32
+#endif /* W_TYPE_SIZE == 32 */
+
+#if W_TYPE_SIZE == 64
+#define count_leading_zeros(COUNT, X) ((COUNT) = __builtin_clzll (X))
+#define count_trailing_zeros(COUNT, X) ((COUNT) = __builtin_ctzll (X))
+#define COUNT_LEADING_ZEROS_0 64
+#endif /* W_TYPE_SIZE == 64 */
+
+#endif /* __aarch64__ */
+