[libc] Add math functions to Windows's entrypoints

[hedingarcia]

Summary

Expanded a list of math functions, that do not depend on the MPFR
library, to be successfully tested in Windows. Placed identifiers
for Windows that disable members that are not needed in FEnv.h.
This was done to meet a static assert of the internal floating point
state and the public fenv_t type to avoid build errors for Windows.
Refactored NextAfterTest.h to correctly define bitWidthOfType
for both Linux and Windows.

[aeubanks]

libc/utils/FPUtil/x86_64/FEnv.h

94

this change isn't obvious and isn't described in the commit description, it'd be nice to add why this change was made

[hedingarcia]

[libc] Fixed commit description and ran clang-format

[sivachandra]

libc/config/windows/entrypoints.txt

69

Can you add nextafter functions in a different patch along with the fix in NextAfterTest.h.

libc/test/src/math/NextAfterTest.h

26

As pointed out above, can you move this to a separate patch?

libc/utils/FPUtil/x86_64/FEnv.h

94

Can you split this into a different patch.

356

Leave this out as this is not the correct fix. We can make another pass, when we enable the fenv functions, to fix these up correctly.

366

Same here.

libc/config/windows/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr
     libc.src.string.strspn
     libc.src.string.strstr
     libc.src.string.strtok
     libc.src.string.strtok_r
 )
+
+set(TARGET_LIBM_ENTRYPOINTS
+    # math.h entrypoints
+    libc.src.math.copysign
+    libc.src.math.copysignf
+    libc.src.math.copysignl
+    libc.src.math.fdimf
+    libc.src.math.fdim
+    libc.src.math.fdiml
+    libc.src.math.fmin
+    libc.src.math.fminf
+    libc.src.math.fminl
+    libc.src.math.fmax
+    libc.src.math.fmaxf
+    libc.src.math.fmaxl
+    libc.src.math.ilogb
+    libc.src.math.ilogbf
+    libc.src.math.ilogbl
+    libc.src.math.ldexp
+    libc.src.math.ldexpf
+    libc.src.math.ldexpl
+    libc.src.math.logb
+    libc.src.math.logbf
+    libc.src.math.logbl
+    libc.src.math.modf
+    libc.src.math.modff
+    libc.src.math.modfl
+    libc.src.math.nextafter
+    libc.src.math.nextafterf
+    libc.src.math.nextafterl
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
+  ${TARGET_LIBM_ENTRYPOINTS}
 )

libc/test/src/math/NextAfterTest.h

 #include <math.h>
 
 template <typename T>
 class NextAfterTestTemplate : public __llvm_libc::testing::Test {
   using FPBits = __llvm_libc::fputil::FPBits<T>;
   using MantissaWidth = __llvm_libc::fputil::MantissaWidth<T>;
   using UIntType = typename FPBits::UIntType;
 
-#if (defined(__x86_64__) || defined(__i386__))
   static constexpr int bitWidthOfType =
-      __llvm_libc::cpp::IsSame<T, long double>::Value ? 80 : (sizeof(T) * 8);
-#else
-  static constexpr int bitWidthOfType = sizeof(T) * 8;
-#endif
+      __llvm_libc::fputil::FloatProperties<T>::bitWidth;
 
   const T zero = T(FPBits::zero());
   const T negZero = T(FPBits::negZero());
   const T inf = T(FPBits::inf());
   const T negInf = T(FPBits::negInf());
   const T nan = T(FPBits::buildNaN(1));
   const UIntType minSubnormal = FPBits::minSubnormal;
   const UIntType maxSubnormal = FPBits::maxSubnormal;

libc/utils/FPUtil/x86_64/FEnv.h

 }
 
 struct X87StateDescriptor {
   uint16_t ControlWord;
   uint16_t Unused1;
   uint16_t StatusWord;
   uint16_t Unused2;
   // TODO: Elaborate the remaining 20 bytes as required.
+#if !(defined(_WIN32) || defined(_WIN64))
   uint32_t _[5];
+#endif
 };
 
 struct FPState {
   X87StateDescriptor X87Status;
+#if !(defined(_WIN32) || defined(_WIN64))
   uint32_t MXCSR;
+#endif
 };
 
 static_assert(
     sizeof(fenv_t) == sizeof(FPState),
     "Internal floating point state does not match the public fenv_t type.");
 
 static inline uint16_t getX87ControlWord() {
   uint16_t w;
static inline int setRound(int mode) {
   internal::writeMXCSR(mxcsrControl);
 
   return 0;
 }
 
 static inline int getEnv(fenv_t *envp) {
   internal::FPState *state = reinterpret_cast<internal::FPState *>(envp);
   internal::getX87StateDescriptor(state->X87Status);
+#if !(defined(_WIN32) || defined(_WIN64))
   state->MXCSR = internal::getMXCSR();
+#endif
   return 0;
 }
 
 static inline int setEnv(const fenv_t *envp) {
   const internal::FPState *state =
       reinterpret_cast<const internal::FPState *>(envp);
   internal::writeX87StateDescriptor(state->X87Status);
+#if !(defined(_WIN32) || defined(_WIN64))
   internal::writeMXCSR(state->MXCSR);
+#endif
   return 0;
 }
 
 } // namespace fputil
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_UTILS_FPUTIL_X86_64_FENV_H