25 lines
665 B
C
25 lines
665 B
C
#include <isl_config.h>
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#if !HAVE_DECL_FFS && !HAVE_DECL___BUILTIN_FFS && HAVE_DECL__BITSCANFORWARD
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#include <intrin.h>
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/* Implementation of ffs in terms of _BitScanForward.
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*
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* ffs returns the position of the least significant bit set in i,
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* with the least significant bit is position 1, or 0 if not bits are set.
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*
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* _BitScanForward returns 1 if mask is non-zero and sets index
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* to the position of the least significant bit set in i,
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* with the least significant bit is position 0.
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*/
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int isl_ffs(int i)
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{
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unsigned char non_zero;
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unsigned long index, mask = i;
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non_zero = _BitScanForward(&index, mask);
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return non_zero ? 1 + index : 0;
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}
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#endif
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