alternative BitScanForward64 implementation

Change-Id: I1d2f388da8414c6cf9401141dfa8e924f6677fd8

Author: rdementi

src/cpucounters.cpp

@@ -41,7 +41,6 @@
 
 #ifdef _MSC_VER
 #include <intrin.h>
-#pragma intrinsic(_BitScanForward64)
 #include <windows.h>
 #include <comdef.h>
 #include <tchar.h>
@@ -7426,9 +7425,19 @@ int32 PCM::mapNUMANodeToSocket(uint32 numa_node_id) const
 
             if (mask != 0)
             {
+                auto BitScanForward64 = [](unsigned long* Index, uint64_t Mask)
+                {
+                    if (Mask == 0) return 0;
+
+                    // Magic numbers for LSB (chess engine style)
+                    static const uint64_t magic = 0x03f79d71b4cb0a89ULL;
+                    uint64_t isolated = Mask & -Mask;  // Rightmost set bit
+                    *Index = (unsigned long)(((isolated * magic) >> 58));
+                };
+
                 // Find first set bit (first processor in this NUMA node within this group)
                 DWORD bitPosition = 0;
-                _BitScanForward64(&bitPosition, mask);
+                BitScanForward64(&bitPosition, mask);
 
                 // On Windows, we need to find the logical processor ID that corresponds to
                 // this bit position in this group. We iterate through topology to find a match.