+ static const char debruijn64[64] = {
+ 0, 1, 2, 53, 3, 7, 54, 27, 4, 38, 41, 8, 34, 55, 48, 28,
+ 62, 5, 39, 46, 44, 42, 22, 9, 24, 35, 59, 56, 49, 18, 29, 11,
+ 63, 52, 6, 26, 37, 40, 33, 47, 61, 45, 43, 21, 23, 58, 17, 10,
+ 51, 25, 36, 32, 60, 20, 57, 16, 50, 31, 19, 15, 30, 14, 13, 12
+ };
+ if (sizeof(long) < 8) {
+ uint32_t y = x;
+ if (!y) {
+ y = x>>32;
+ return 32 + a_ctz_32(y);
+ }
+ return a_ctz_32(y);
+ }
+ return debruijn64[(x&-x)*0x022fdd63cc95386dull >> 58];