1 #include <isl_config.h>
2 
3 #if !HAVE_DECL_FFS && !HAVE_DECL___BUILTIN_FFS && HAVE_DECL__BITSCANFORWARD
4 #include <intrin.h>
5 
6 /* Implementation of ffs in terms of _BitScanForward.
7  *
8  * ffs returns the position of the least significant bit set in i,
9  * with the least significant bit is position 1, or 0 if not bits are set.
10  *
11  * _BitScanForward returns 1 if mask is non-zero and sets index
12  * to the position of the least significant bit set in i,
13  * with the least significant bit is position 0.
14  */
isl_ffs(int i)15 int isl_ffs(int i)
16 {
17 	unsigned char non_zero;
18 	unsigned long index, mask = i;
19 
20 	non_zero = _BitScanForward(&index, mask);
21 
22 	return non_zero ? 1 + index : 0;
23 }
24 #endif
25