diff --git a/include/llvm/Support/MathExtras.h b/include/llvm/Support/MathExtras.h
index 10911ea11c5..eaab8abe076 100644
--- a/include/llvm/Support/MathExtras.h
+++ b/include/llvm/Support/MathExtras.h
@@ -16,6 +16,10 @@
 
 #include "llvm/Support/SwapByteOrder.h"
 
+#ifdef _MSC_VER
+# include <intrin.h>
+#endif
+
 namespace llvm {
 
 // NOTE: The following support functions use the _32/_64 extensions instead of
@@ -299,7 +303,7 @@ inline unsigned CountTrailingOnes_64(uint64_t Value) {
 inline unsigned CountPopulation_32(uint32_t Value) {
 #if __GNUC__ >= 4
   return __builtin_popcount(Value);
-#elif _MSC_VER
+#elif defined(_MSC_VER)
   return __popcnt(Value);
 #else
   uint32_t v = Value - ((Value >> 1) & 0x55555555);
@@ -313,7 +317,7 @@ inline unsigned CountPopulation_32(uint32_t Value) {
 inline unsigned CountPopulation_64(uint64_t Value) {
 #if __GNUC__ >= 4
   return __builtin_popcountll(Value);
-#elif _MSC_VER
+#elif defined(_MSC_VER)
   return __popcnt64(Value);
 #else
   uint64_t v = Value - ((Value >> 1) & 0x5555555555555555ULL);