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Enable _BitScanForward64 at runtime

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Only add infrastructure, still disabled.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-05-24 09:46:43 +01:00
parent ce5d9eb19d
commit f90f810ac4
3 changed files with 26 additions and 2 deletions
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24
src/bitcount.h
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@@ -66,6 +66,7 @@ inline bool cpu_has_popcnt() {
}
#define POPCNT_INTRINSIC(x) __popcnt64(x)
#define BITSCAN_INTRINSIC(idx, x) _BitScanForward64(idx, x)
#elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
@@ -79,12 +80,14 @@ inline bool cpu_has_popcnt() {
}
#define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
#define BITSCAN_INTRINSIC(idx, x) _BitScanForward64(idx, x)
#else // Safe fallback for unsupported compilers
inline bool cpu_has_popcnt() { return false; }
#define POPCNT_INTRINSIC(x) sw_count_1s(x)
#define BITSCAN_INTRINSIC(idx, x) sw_count_1s(x) // dummy
#endif
@@ -183,4 +186,25 @@ const bool CpuHas64BitPath = true;
const bool CpuHas64BitPath = false;
#endif
/// pop_1st_bit() finds and clears the least significant nonzero bit in a
/// nonzero bitboard. If template parameter is true an intrinsic is called,
/// otherwise we fallback on a software implementation.
template<bool UseIntrinsic>
inline Square pop_1st_bit(Bitboard *b) {
return pop_1st_bit(b);
}
template<>
inline Square pop_1st_bit<true>(Bitboard *b) {
unsigned long idx;
Bitboard bb = *b;
BITSCAN_INTRINSIC(&idx, bb);
*b &= (bb - 1);
return Square(idx);
}
#endif // !defined(BITCOUNT_H_INCLUDED)