diff --git a/libc/utils/FPUtil/FPBits.h b/libc/utils/FPUtil/FPBits.h
index bc69829ca720ca..2e05c231202924 100644
--- a/libc/utils/FPUtil/FPBits.h
+++ b/libc/utils/FPUtil/FPBits.h
@@ -9,6 +9,8 @@
 #ifndef LLVM_LIBC_UTILS_FPUTIL_FP_BITS_H
 #define LLVM_LIBC_UTILS_FPUTIL_FP_BITS_H
 
+#include "PlatformDefs.h"
+
 #include "utils/CPP/TypeTraits.h"
 
 #include <stdint.h>
@@ -39,13 +41,17 @@ template <typename T> struct FPUIntType {};
 template <> struct FPUIntType<float> { using Type = uint32_t; };
 template <> struct FPUIntType<double> { using Type = uint64_t; };
 
-#if !(defined(__x86_64__) || defined(__i386__))
-// TODO: This has to be extended for visual studio where long double and
-// double are equivalent.
+#ifdef LONG_DOUBLE_IS_DOUBLE
+template <> struct MantissaWidth<long double> {
+  static constexpr unsigned value = MantissaWidth<double>::value;
+};
+template <> struct FPUIntType<long double> {
+  using Type = FPUIntType<double>::Type;
+};
+#elif !defined(SPECIAL_X86_LONG_DOUBLE)
 template <> struct MantissaWidth<long double> {
   static constexpr unsigned value = 112;
 };
-
 template <> struct FPUIntType<long double> { using Type = __uint128_t; };
 #endif
 
@@ -150,7 +156,7 @@ template <typename T> union FPBits {
 } // namespace fputil
 } // namespace __llvm_libc
 
-#if defined(__x86_64__) || defined(__i386__)
+#ifdef SPECIAL_X86_LONG_DOUBLE
 #include "utils/FPUtil/LongDoubleBitsX86.h"
 #endif
 
diff --git a/libc/utils/FPUtil/ManipulationFunctions.h b/libc/utils/FPUtil/ManipulationFunctions.h
index 9bd54ec3e979df..2dfd8e1b71084c 100644
--- a/libc/utils/FPUtil/ManipulationFunctions.h
+++ b/libc/utils/FPUtil/ManipulationFunctions.h
@@ -12,6 +12,7 @@
 #include "FPBits.h"
 #include "NearestIntegerOperations.h"
 #include "NormalFloat.h"
+#include "PlatformDefs.h"
 
 #include "utils/CPP/TypeTraits.h"
 
@@ -178,8 +179,8 @@ static inline T nextafter(T from, T to) {
 } // namespace fputil
 } // namespace __llvm_libc
 
-#if (defined(__x86_64__) || defined(__i386__))
+#ifdef SPECIAL_X86_LONG_DOUBLE
 #include "NextAfterLongDoubleX86.h"
-#endif // defined(__x86_64__) || defined(__i386__)
+#endif // SPECIAL_X86_LONG_DOUBLE
 
 #endif // LLVM_LIBC_UTILS_FPUTIL_MANIPULATION_FUNCTIONS_H
diff --git a/libc/utils/FPUtil/NormalFloat.h b/libc/utils/FPUtil/NormalFloat.h
index 07bb91bc4fd99c..c0fb85746f70a3 100644
--- a/libc/utils/FPUtil/NormalFloat.h
+++ b/libc/utils/FPUtil/NormalFloat.h
@@ -169,7 +169,7 @@ template <typename T> struct NormalFloat {
   }
 };
 
-#if defined(__x86_64__) || defined(__i386__)
+#ifdef SPECIAL_X86_LONG_DOUBLE
 template <>
 inline void NormalFloat<long double>::initFromBits(FPBits<long double> bits) {
   sign = bits.encoding.sign;
@@ -256,7 +256,7 @@ template <> inline NormalFloat<long double>::operator long double() const {
   result.encoding.implicitBit = 1;
   return static_cast<long double>(result);
 }
-#endif
+#endif // SPECIAL_X86_LONG_DOUBLE
 
 } // namespace fputil
 } // namespace __llvm_libc
diff --git a/libc/utils/FPUtil/PlatformDefs.h b/libc/utils/FPUtil/PlatformDefs.h
new file mode 100644
index 00000000000000..30ed24d4fdda60
--- /dev/null
+++ b/libc/utils/FPUtil/PlatformDefs.h
@@ -0,0 +1,24 @@
+//===-- Platform specific macro definitions ---------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_UTILS_FPUTIL_PLATFORM_DEFS_H
+#define LLVM_LIBC_UTILS_FPUTIL_PLATFORM_DEFS_H
+
+#if defined(__x86_64__) || defined(__i386__)
+#define X87_FPU
+#endif
+
+#if defined(_WIN32) || defined(_WIN64)
+#define LONG_DOUBLE_IS_DOUBLE
+#endif
+
+#if !defined(LONG_DOUBLE_IS_DOUBLE) && defined(X87_FPU)
+#define SPECIAL_X86_LONG_DOUBLE
+#endif
+
+#endif // LLVM_LIBC_UTILS_FPUTIL_PLATFORM_DEFS_H
diff --git a/libc/utils/FPUtil/Sqrt.h b/libc/utils/FPUtil/Sqrt.h
index 097818ca031391..2986e8483bde50 100644
--- a/libc/utils/FPUtil/Sqrt.h
+++ b/libc/utils/FPUtil/Sqrt.h
@@ -10,6 +10,7 @@
 #define LLVM_LIBC_UTILS_FPUTIL_SQRT_H
 
 #include "FPBits.h"
+#include "PlatformDefs.h"
 
 #include "utils/CPP/TypeTraits.h"
 
@@ -61,7 +62,12 @@ template <> inline void normalize<double>(int &exponent, uint64_t &mantissa) {
   }
 }
 
-#if !(defined(__x86_64__) || defined(__i386__))
+#ifdef LONG_DOUBLE_IS_DOUBLE
+template <>
+inline void normalize<long double>(int &exponent, uint64_t &mantissa) {
+  normalize<double>(exponent, mantissa);
+}
+#elif !defined(SPECIAL_X86_LONG_DOUBLE)
 template <>
 inline void normalize<long double>(int &exponent, __uint128_t &mantissa) {
   // Use binary search to shift the leading 1 bit similar to float.
@@ -179,8 +185,8 @@ static inline T sqrt(T x) {
 } // namespace fputil
 } // namespace __llvm_libc
 
-#if (defined(__x86_64__) || defined(__i386__))
+#ifdef SPECIAL_X86_LONG_DOUBLE
 #include "SqrtLongDoubleX86.h"
-#endif // defined(__x86_64__) || defined(__i386__)
+#endif // SPECIAL_X86_LONG_DOUBLE
 
 #endif // LLVM_LIBC_UTILS_FPUTIL_SQRT_H
diff --git a/libc/utils/FPUtil/SqrtLongDoubleX86.h b/libc/utils/FPUtil/SqrtLongDoubleX86.h
index 8ea4ea5a9c4705..953c4a476105f3 100644
--- a/libc/utils/FPUtil/SqrtLongDoubleX86.h
+++ b/libc/utils/FPUtil/SqrtLongDoubleX86.h
@@ -17,7 +17,6 @@
 namespace __llvm_libc {
 namespace fputil {
 
-#if (defined(__x86_64__) || defined(__i386__))
 namespace internal {
 
 template <>
@@ -136,7 +135,6 @@ template <> inline long double sqrt<long double, 0>(long double x) {
     return out;
   }
 }
-#endif // defined(__x86_64__) || defined(__i386__)
 
 } // namespace fputil
 } // namespace __llvm_libc