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