return (x * 0x0101010101010101ULL) >> 56;
}
-#ifdef __GNUC__
+/* __builtin_ctzll was not available until 3.4.0 */
+#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR > 3))
#define ewah_bit_ctz64(x) __builtin_ctzll(x)
#else
static inline int ewah_bit_ctz64(uint64_t x)