[llvm] Deprecate {Bits,Float,Double}To{Bits,Float,Double} (NFC)

[RKSimon]

LGTM - cheers

llvm/include/llvm/Support/MathExtras.h

 
 /// Return the ceil log base 2 of the specified value, 64 if the value is zero.
 /// (64 bit edition.)
 inline unsigned Log2_64_Ceil(uint64_t Value) {
   return 64 - llvm::countl_zero(Value - 1);
 }
 
 /// This function takes a 64-bit integer and returns the bit equivalent double.
+LLVM_DEPRECATED("use llvm::bit_cast instead", "llvm::bit_cast<double>")
 inline double BitsToDouble(uint64_t Bits) {
   static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
   return llvm::bit_cast<double>(Bits);
 }
 
 /// This function takes a 32-bit integer and returns the bit equivalent float.
+LLVM_DEPRECATED("use llvm::bit_cast instead", "llvm::bit_cast<float>")
 inline float BitsToFloat(uint32_t Bits) {
   static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
   return llvm::bit_cast<float>(Bits);
 }
 
 /// This function takes a double and returns the bit equivalent 64-bit integer.
 /// Note that copying doubles around changes the bits of NaNs on some hosts,
 /// notably x86, so this routine cannot be used if these bits are needed.
+LLVM_DEPRECATED("use llvm::bit_cast instead", "llvm::bit_cast<uint64_t>")
 inline uint64_t DoubleToBits(double Double) {
   static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
   return llvm::bit_cast<uint64_t>(Double);
 }
 
 /// This function takes a float and returns the bit equivalent 32-bit integer.
 /// Note that copying floats around changes the bits of NaNs on some hosts,
 /// notably x86, so this routine cannot be used if these bits are needed.
+LLVM_DEPRECATED("use llvm::bit_cast instead", "llvm::bit_cast<uint32_t>")
 inline uint32_t FloatToBits(float Float) {
   static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
   return llvm::bit_cast<uint32_t>(Float);
 }
 
 /// A and B are either alignments or offsets. Return the minimum alignment that
 /// may be assumed after adding the two together.
 constexpr inline uint64_t MinAlign(uint64_t A, uint64_t B) {

llvm/unittests/Support/MathExtrasTest.cpp

TEST(MathExtras, CTLog2) {
   EXPECT_EQ(CTLog2<1ULL << 10>(), 10U);
   EXPECT_EQ(CTLog2<1ULL << 11>(), 11U);
   EXPECT_EQ(CTLog2<1ULL << 12>(), 12U);
   EXPECT_EQ(CTLog2<1ULL << 13>(), 13U);
   EXPECT_EQ(CTLog2<1ULL << 14>(), 14U);
   EXPECT_EQ(CTLog2<1ULL << 15>(), 15U);
 }
 
-TEST(MathExtras, FloatBits) {
-  static const float kValue = 5632.34f;
-  EXPECT_FLOAT_EQ(kValue, BitsToFloat(FloatToBits(kValue)));
-}
-
-TEST(MathExtras, DoubleBits) {
-  static const double kValue = 87987234.983498;
-  EXPECT_DOUBLE_EQ(kValue, BitsToDouble(DoubleToBits(kValue)));
-}
-
 TEST(MathExtras, MinAlign) {
   EXPECT_EQ(1u, MinAlign(2, 3));
   EXPECT_EQ(2u, MinAlign(2, 4));
   EXPECT_EQ(1u, MinAlign(17, 64));
   EXPECT_EQ(256u, MinAlign(256, 512));
 }
 
 TEST(MathExtras, NextPowerOf2) {