Index: llvm/include/llvm/Support/MathExtras.h
===================================================================
--- llvm/include/llvm/Support/MathExtras.h
+++ llvm/include/llvm/Support/MathExtras.h
@@ -35,6 +35,8 @@
 unsigned char _BitScanForward64(unsigned long *_Index, unsigned __int64 _Mask);
 unsigned char _BitScanReverse(unsigned long *_Index, unsigned long _Mask);
 unsigned char _BitScanReverse64(unsigned long *_Index, unsigned __int64 _Mask);
+unsigned int __popcnt(unsigned int);
+unsigned __int64 __popcnt64(unsigned __int64);
 }
 #endif
 
@@ -525,6 +527,9 @@
     static_assert(SizeOfT <= 4, "Not implemented!");
 #if defined(__GNUC__)
     return __builtin_popcount(Value);
+#elif defined(_MSC_VER) && _MSC_VER >= 1500 &&                                 \
+    (defined(_M_IX86) || defined(_M_X64))
+    return __popcnt(Value);
 #else
     uint32_t v = Value;
     v = v - ((v >> 1) & 0x55555555);
@@ -538,6 +543,8 @@
   static unsigned count(T Value) {
 #if defined(__GNUC__)
     return __builtin_popcountll(Value);
+#elif defined(_MSC_VER) && _MSC_VER >= 1500 && defined(_M_X64)
+    return (unsigned)__popcnt64(Value);
 #else
     uint64_t v = Value;
     v = v - ((v >> 1) & 0x5555555555555555ULL);