| //===-- Abstract class for bit manipulation of float numbers. ---*- 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_FP_BITS_H |
| #define LLVM_LIBC_UTILS_FPUTIL_FP_BITS_H |
| |
| #include "utils/CPP/TypeTraits.h" |
| |
| #include <stdint.h> |
| |
| namespace __llvm_libc { |
| namespace fputil { |
| |
| template <typename T> struct MantissaWidth {}; |
| template <> struct MantissaWidth<float> { |
| static constexpr unsigned value = 23; |
| }; |
| template <> struct MantissaWidth<double> { |
| static constexpr unsigned value = 52; |
| }; |
| |
| template <typename T> struct ExponentWidth {}; |
| template <> struct ExponentWidth<float> { |
| static constexpr unsigned value = 8; |
| }; |
| template <> struct ExponentWidth<double> { |
| static constexpr unsigned value = 11; |
| }; |
| template <> struct ExponentWidth<long double> { |
| static constexpr unsigned value = 15; |
| }; |
| |
| 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. |
| template <> struct MantissaWidth<long double> { |
| static constexpr unsigned value = 112; |
| }; |
| |
| template <> struct FPUIntType<long double> { using Type = __uint128_t; }; |
| #endif |
| |
| // A generic class to represent single precision, double precision, and quad |
| // precision IEEE 754 floating point formats. |
| // On most platforms, the 'float' type corresponds to single precision floating |
| // point numbers, the 'double' type corresponds to double precision floating |
| // point numers, and the 'long double' type corresponds to the quad precision |
| // floating numbers. On x86 platforms however, the 'long double' type maps to |
| // an x87 floating point format. This format is an IEEE 754 extension format. |
| // It is handled as an explicit specialization of this class. |
| template <typename T> struct __attribute__((packed)) FPBits { |
| static_assert(cpp::IsFloatingPointType<T>::Value, |
| "FPBits instantiated with invalid type."); |
| |
| // Reinterpreting bits as an integer value and interpreting the bits of an |
| // integer value as a floating point value is used in tests. So, a convenient |
| // type is provided for such reinterpretations. |
| using UIntType = typename FPUIntType<T>::Type; |
| |
| UIntType mantissa : MantissaWidth<T>::value; |
| uint16_t exponent : ExponentWidth<T>::value; |
| uint8_t sign : 1; |
| |
| static constexpr int exponentBias = (1 << (ExponentWidth<T>::value - 1)) - 1; |
| static constexpr int maxExponent = (1 << ExponentWidth<T>::value) - 1; |
| |
| // We don't want accidental type promotions/conversions so we require exact |
| // type match. |
| template <typename XType, |
| cpp::EnableIfType<cpp::IsSame<T, XType>::Value, int> = 0> |
| explicit FPBits(XType x) { |
| *this = *reinterpret_cast<FPBits<T> *>(&x); |
| } |
| |
| operator T() { return *reinterpret_cast<T *>(this); } |
| |
| int getExponent() const { return int(exponent) - exponentBias; } |
| |
| bool isZero() const { return mantissa == 0 && exponent == 0; } |
| |
| bool isInf() const { return mantissa == 0 && exponent == maxExponent; } |
| |
| bool isNaN() const { return exponent == maxExponent && mantissa != 0; } |
| |
| bool isInfOrNaN() const { return exponent == maxExponent; } |
| |
| // Methods below this are used by tests. |
| // The to and from integer bits converters are only used in tests. Hence, |
| // the potential software implementations of UIntType will not slow real |
| // code. |
| |
| template <typename XType, |
| cpp::EnableIfType<cpp::IsSame<UIntType, XType>::Value, int> = 0> |
| explicit FPBits<long double>(XType x) { |
| // The last 4 bytes of v are ignored in case of i386. |
| *this = *reinterpret_cast<FPBits<T> *>(&x); |
| } |
| |
| UIntType bitsAsUInt() const { |
| return *reinterpret_cast<const UIntType *>(this); |
| } |
| |
| static FPBits<T> zero() { return FPBits(T(0.0)); } |
| |
| static FPBits<T> negZero() { |
| FPBits<T> bits(T(0.0)); |
| bits.sign = 1; |
| return bits; |
| } |
| |
| static FPBits<T> inf() { |
| FPBits<T> bits(T(0.0)); |
| bits.exponent = maxExponent; |
| return bits; |
| } |
| |
| static FPBits<T> negInf() { |
| FPBits<T> bits(T(0.0)); |
| bits.exponent = maxExponent; |
| bits.sign = 1; |
| return bits; |
| } |
| |
| static T buildNaN(UIntType v) { |
| FPBits<T> bits(T(0.0)); |
| bits.exponent = maxExponent; |
| bits.mantissa = v; |
| return bits; |
| } |
| }; |
| |
| } // namespace fputil |
| } // namespace __llvm_libc |
| |
| #if defined(__x86_64__) || defined(__i386__) |
| #include "utils/FPUtil/LongDoubleBitsX86.h" |
| #endif |
| |
| #endif // LLVM_LIBC_UTILS_FPUTIL_FP_BITS_H |