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 */
15int 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

source code of polly/lib/External/isl/isl_ffs.c