- that table counted trailing zeros rather than bit position. */
- static unsigned int table[] = {
- 1, 2, 29, 3, 30, 15, 25, 4, 31, 23, 21, 16, 26, 18, 5, 9,
- 32, 28, 14, 24, 22, 20, 17, 8, 27, 13, 19, 7, 12, 6, 11, 10
- };
- unsigned int u = i;
- unsigned int bit = u & -u;
- return table[(bit * 0x077cb531U) >> 27] - !i;
+ that table counted trailing zeros rather than bit position. This
+ requires 32-bit int, we fall back to a naive algorithm on the rare
+ platforms where that assumption is not true. */
+ if (CHAR_BIT * sizeof i == 32)
+ {
+ static unsigned int table[] = {
+ 1, 2, 29, 3, 30, 15, 25, 4, 31, 23, 21, 16, 26, 18, 5, 9,
+ 32, 28, 14, 24, 22, 20, 17, 8, 27, 13, 19, 7, 12, 6, 11, 10
+ };
+ unsigned int u = i;
+ unsigned int bit = u & -u;
+ return table[(bit * 0x077cb531U) >> 27] - !i;
+ }
+ else
+ {
+ unsigned int j;
+ for (j = 0; j < CHAR_BIT * sizeof i; j++)
+ if (i & (1U << j))
+ return j + 1;
+ return 0;
+ }