}
-/// lsb() and msb() return the least/most significant bit in a non-zero bitboard
+/// popcount() counts the number of non-zero bits in a bitboard
-#ifdef USE_BSFQ
+inline int popcount(Bitboard b) {
-# if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
+#ifndef USE_POPCNT
-inline Square lsb(Bitboard b) {
- unsigned long idx;
- _BitScanForward64(&idx, b);
- return (Square) idx;
-}
+ extern uint8_t PopCnt16[1 << 16];
+ union { Bitboard bb; uint16_t u[4]; } v = { b };
+ return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
-inline Square msb(Bitboard b) {
- unsigned long idx;
- _BitScanReverse64(&idx, b);
- return (Square) idx;
-}
+#elif defined(_MSC_VER) && defined(__INTEL_COMPILER)
-# elif defined(__arm__)
+ return _mm_popcnt_u64(b);
-inline int lsb32(uint32_t v) {
- __asm__("rbit %0, %1" : "=r"(v) : "r"(v));
- return __builtin_clz(v);
-}
+#elif defined(_MSC_VER)
-inline Square msb(Bitboard b) {
- return (Square) (63 - __builtin_clzll(b));
+ return (int)__popcnt64(b);
+
+#else // Assumed gcc or compatible compiler
+
+ return __builtin_popcountll(b);
+
+#endif
}
+
+/// lsb() and msb() return the least/most significant bit in a non-zero bitboard
+
+#if defined(__GNUC__)
+
inline Square lsb(Bitboard b) {
- return (Square) (uint32_t(b) ? lsb32(uint32_t(b)) : 32 + lsb32(uint32_t(b >> 32)));
+ assert(b);
+ return Square(__builtin_ctzll(b));
+}
+
+inline Square msb(Bitboard b) {
+ assert(b);
+ return Square(63 - __builtin_clzll(b));
}
-# else // Assumed gcc or compatible compiler
+#elif defined(_WIN64) && defined(_MSC_VER)
-inline Square lsb(Bitboard b) { // Assembly code by Heinz van Saanen
- Bitboard idx;
- __asm__("bsfq %1, %0": "=r"(idx): "rm"(b) );
+inline Square lsb(Bitboard b) {
+ assert(b);
+ unsigned long idx;
+ _BitScanForward64(&idx, b);
return (Square) idx;
}
inline Square msb(Bitboard b) {
- Bitboard idx;
- __asm__("bsrq %1, %0": "=r"(idx): "rm"(b) );
+ assert(b);
+ unsigned long idx;
+ _BitScanReverse64(&idx, b);
return (Square) idx;
}
-# endif
+#else
-#else // ifdef(USE_BSFQ)
+#define NO_BSF // Fallback on software implementation for other cases
Square lsb(Bitboard b);
Square msb(Bitboard b);