diff --git a/libc/utils/FPUtil/FloatProperties.h b/libc/utils/FPUtil/FloatProperties.h
--- a/libc/utils/FPUtil/FloatProperties.h
+++ b/libc/utils/FPUtil/FloatProperties.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_UTILS_FPUTIL_FLOAT_PROPERTIES_H
 #define LLVM_LIBC_UTILS_FPUTIL_FLOAT_PROPERTIES_H
 
+#include "PlatformDefs.h"
 #include <stdint.h>
 
 namespace __llvm_libc {
@@ -24,10 +25,12 @@
   static constexpr uint32_t bitWidth = sizeof(BitsType) << 3;
 
   static constexpr uint32_t mantissaWidth = 23;
-  static constexpr BitsType mantissaMask = 0x007fffffU;
-  static constexpr BitsType signMask = 0x80000000U;
+  static constexpr uint32_t exponentWidth = 8;
+  static constexpr BitsType mantissaMask = (BitsType(1) << mantissaWidth) - 1;
+  static constexpr BitsType signMask = BitsType(1)
+                                       << (exponentWidth + mantissaWidth);
   static constexpr BitsType exponentMask = ~(signMask | mantissaMask);
-  static constexpr uint32_t exponentOffset = 127;
+  static constexpr uint32_t exponentBias = 127;
 
   // If a number x is a NAN, then it is a quiet NAN if:
   //   QuietNaNMask & bits(x) != 0
@@ -43,10 +46,12 @@
   static constexpr uint32_t bitWidth = sizeof(BitsType) << 3;
 
   static constexpr uint32_t mantissaWidth = 52;
-  static constexpr BitsType mantissaMask = 0x000fffffffffffffU;
-  static constexpr BitsType signMask = 0x8000000000000000ULL;
+  static constexpr uint32_t exponentWidth = 11;
+  static constexpr BitsType mantissaMask = (BitsType(1) << mantissaWidth) - 1;
+  static constexpr BitsType signMask = BitsType(1)
+                                       << (exponentWidth + mantissaWidth);
   static constexpr BitsType exponentMask = ~(signMask | mantissaMask);
-  static constexpr uint32_t exponentOffset = 1023;
+  static constexpr uint32_t exponentBias = 1023;
 
   // If a number x is a NAN, then it is a quiet NAN if:
   //   QuietNaNMask & bits(x) != 0
@@ -54,6 +59,67 @@
   static constexpr BitsType quietNaNMask = 0x0008000000000000ULL;
 };
 
+#if defined(LONG_DOUBLE_IS_DOUBLE)
+// Properties for numbers represented in 64 bits long double on Windows
+// platform.
+template <> struct FloatProperties<long double> {
+  typedef uint64_t BitsType;
+  static_assert(sizeof(BitsType) == sizeof(double),
+                "Unexpected size of 'double' type.");
+
+  static constexpr uint32_t bitWidth = FloatProperties<double>::bitWidth;
+
+  static constexpr uint32_t mantissaWidth =
+      FloatProperties<double>::mantissaWidth;
+  static constexpr uint32_t exponentWidth =
+      FloatProperties<double>::exponentWidth;
+  static constexpr BitsType mantissaMask =
+      FloatProperties<double>::mantissaMask;
+  static constexpr BitsType signMask = FloatProperties<double>::signMask;
+  static constexpr BitsType exponentMask =
+      FloatProperties<double>::exponentMask;
+  static constexpr uint32_t exponentBias =
+      FloatProperties<double>::exponentBias;
+};
+#elif defined(SPECIAL_X86_LONG_DOUBLE)
+// Properties for numbers represented in 80 bits long double on non-Windows x86
+// platforms.
+template <> struct FloatProperties<long double> {
+  typedef __uint128_t BitsType;
+  static_assert(sizeof(BitsType) == sizeof(long double),
+                "Unexpected size of 'long double' type.");
+
+  static constexpr uint32_t bitWidth = (sizeof(BitsType) << 3) - 48;
+
+  static constexpr uint32_t mantissaWidth = 63;
+  static constexpr uint32_t exponentWidth = 15;
+  static constexpr BitsType mantissaMask = (BitsType(1) << mantissaWidth) - 1;
+  static constexpr BitsType signMask = BitsType(1)
+                                       << (exponentWidth + mantissaWidth + 1);
+  static constexpr BitsType exponentMask = ((BitsType(1) << exponentWidth) - 1)
+                                           << (mantissaWidth + 1);
+  static constexpr uint32_t exponentBias = 16383;
+};
+#else
+// Properties for numbers represented in 128 bits long double on non x86
+// platform.
+template <> struct FloatProperties<long double> {
+  typedef __uint128_t BitsType;
+  static_assert(sizeof(BitsType) == sizeof(long double),
+                "Unexpected size of 'long double' type.");
+
+  static constexpr uint32_t bitWidth = sizeof(BitsType) << 3;
+
+  static constexpr uint32_t mantissaWidth = 112;
+  static constexpr uint32_t exponentWidth = 15;
+  static constexpr BitsType mantissaMask = (BitsType(1) << mantissaWidth) - 1;
+  static constexpr BitsType signMask = BitsType(1)
+                                       << (exponentWidth + mantissaWidth);
+  static constexpr BitsType exponentMask = ~(signMask | mantissaMask);
+  static constexpr uint32_t exponentBias = 16383;
+};
+#endif
+
 // Define the float type corresponding to the BitsType.
 template <typename BitsType> struct FloatType;