-#if defined(__INTEL_COMPILER) && defined(USE_POPCNT) // Intel compiler
-
-inline bool cpu_has_popcnt() {
-
- int CPUInfo[4] = {-1};
- __cpuid(CPUInfo, 0x00000001);
- return (CPUInfo[2] >> 23) & 1;
-}
-
-#define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
-
-#elif defined(_MSC_VER) && defined(USE_POPCNT) // Microsoft compiler
-
-inline bool cpu_has_popcnt() {
-
- int CPUInfo[4] = {-1};
- __cpuid(CPUInfo, 0x00000001);
- return (CPUInfo[2] >> 23) & 1;
-}
-
-#define POPCNT_INTRINSIC(x) (int)__popcnt64(x)
-
-#elif defined(__GNUC__) && defined(USE_POPCNT) // Gcc compiler
-
-inline bool cpu_has_popcnt() {
-
- unsigned int eax, ebx, ecx, edx;
- __cpuid(1, &eax, &ebx, &ecx, &edx);
- return (ecx >> 23) & 1;
-}
-
-#define POPCNT_INTRINSIC(x) ({ \
- unsigned long __ret; \
- __asm__("popcnt %1, %0" : "=r" (__ret) : "r" (x)); \
- __ret; })
-
-#else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled
-
-inline bool cpu_has_popcnt() { return false; }
-
-#define POPCNT_INTRINSIC(x) 0
-
-#endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions
-
-
-/// Software implementation of bit count functions
-
-#if defined(IS_64BIT)
-
-inline int count_1s(Bitboard b) {
+/// count_1s() counts the number of nonzero bits in a bitboard.
+/// We have different optimized versions according if platform
+/// is 32 or 64 bits, and to the maximum number of nonzero bits.
+/// We also support hardware popcnt instruction. See Readme.txt
+/// on how to pgo compile with popcnt support.
+template<BitCountType> inline int count_1s(Bitboard);
+
+template<>
+inline int count_1s<CNT64>(Bitboard b) {