libc/utils/FPUtil/FloatProperties.h

   1 //===-- Properties of floating point numbers --------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_UTILS_FPUTIL_FLOAT_PROPERTIES_H
  10 #define LLVM_LIBC_UTILS_FPUTIL_FLOAT_PROPERTIES_H
  11
  12 #include <stdint.h>
  13
  14 namespace __llvm_libc {
  15 namespace fputil {
  16
  17 template <typename T> struct FloatProperties {};
  18
  19 template <> struct FloatProperties<float> {
  20   typedef uint32_t BitsType;
  21   static_assert(sizeof(BitsType) == sizeof(float),
  22                 "Unexpected size of 'float' type.");
  23
  24   static constexpr uint32_t mantissaWidth = 23;
  25   static constexpr BitsType mantissaMask = 0x007fffffU;
  26   static constexpr BitsType signMask = 0x80000000U;
  27   static constexpr uint32_t exponentOffset = 127;
  28
  29   // If a number x is a NAN, then it is a quiet NAN if:
  30   //   QuietNaNMask & bits(x) != 0
  31   // Else, it is a signalling NAN.
  32   static constexpr BitsType quietNaNMask = 0x00400000U;
  33 };
  34
  35 template <> struct FloatProperties<double> {
  36   typedef uint64_t BitsType;
  37   static_assert(sizeof(BitsType) == sizeof(double),
  38                 "Unexpected size of 'double' type.");
  39
  40   static constexpr uint32_t mantissaWidth = 52;
  41   static constexpr BitsType mantissaMask = 0x000fffffffffffffU;
  42   static constexpr BitsType signMask = 0x8000000000000000ULL;
  43   static constexpr uint32_t exponentOffset = 1023;
  44
  45   // If a number x is a NAN, then it is a quiet NAN if:
  46   //   QuietNaNMask & bits(x) != 0
  47   // Else, it is a signalling NAN.
  48   static constexpr BitsType quietNaNMask = 0x0008000000000000ULL;
  49 };
  50
  51 // Define the float type corresponding to the BitsType.
  52 template <typename BitsType> struct FloatType;
  53
  54 template <> struct FloatType<uint32_t> {
  55   static_assert(sizeof(uint32_t) == sizeof(float),
  56                 "Unexpected size of 'float' type.");
  57   typedef float Type;
  58 };
  59
  60 template <> struct FloatType<uint64_t> {
  61   static_assert(sizeof(uint64_t) == sizeof(double),
  62                 "Unexpected size of 'double' type.");
  63   typedef double Type;
  64 };
  65
  66 template <typename BitsType>
  67 using FloatTypeT = typename FloatType<BitsType>::Type;
  68
  69 } // namespace fputil
  70 } // namespace __llvm_libc
  71
  72 #endif // LLVM_LIBC_UTILS_FPUTIL_FLOAT_PROPERTIES_H