diff --git a/include/support/win32/support.h b/include/support/win32/support.h
index 6ffd3d25..38ea51e4 100644
--- a/include/support/win32/support.h
+++ b/include/support/win32/support.h
@@ -52,9 +52,32 @@ _LIBCPP_ALWAYS_INLINE long double strtold( const char *nptr, char **endptr )
 
 #ifndef __clang__ // MSVC-based Clang also defines _MSC_VER
 #include <intrin.h>
-#define __builtin_popcount __popcnt
-#define __builtin_popcountl __popcnt
-#define __builtin_popcountll(__i) static_cast<int>(__popcnt64(__i))
+
+_LIBCPP_ALWAYS_INLINE int __builtin_popcount(unsigned int x) {
+   static const unsigned int m1 = 0x55555555; //binary: 0101...
+   static const unsigned int m2 = 0x33333333; //binary: 00110011..
+   static const unsigned int m4 = 0x0f0f0f0f; //binary:  4 zeros,  4 ones ...
+   static const unsigned int h01= 0x01010101; //the sum of 256 to the power of 0,1,2,3...
+   x -= (x >> 1) & m1;             //put count of each 2 bits into those 2 bits
+   x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
+   x = (x + (x >> 4)) & m4;        //put count of each 8 bits into those 8 bits
+   return (x * h01) >> 24;  //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24)
+}
+
+_LIBCPP_ALWAYS_INLINE int __builtin_popcountl(unsigned long x) {
+  return __builtin_popcount(static_cast<int>(x));
+}
+
+_LIBCPP_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x) {
+   static const unsigned long long m1  = 0x5555555555555555; //binary: 0101...
+   static const unsigned long long m2  = 0x3333333333333333; //binary: 00110011..
+   static const unsigned long long m4  = 0x0f0f0f0f0f0f0f0f; //binary:  4 zeros,  4 ones ...
+   static const unsigned long long h01 = 0x0101010101010101; //the sum of 256 to the power of 0,1,2,3...
+   x -= (x >> 1) & m1;             //put count of each 2 bits into those 2 bits
+   x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
+   x = (x + (x >> 4)) & m4;        //put count of each 8 bits into those 8 bits
+   return static_cast<int>((x * h01)>>56);  //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ...
+}
 
 _LIBCPP_ALWAYS_INLINE int __builtin_ctz( unsigned int x )
 {