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Diffstat (limited to 'include/float_utils.h')
| -rw-r--r-- | include/float_utils.h | 533 |
1 files changed, 0 insertions, 533 deletions
diff --git a/include/float_utils.h b/include/float_utils.h deleted file mode 100644 index 831ad74..0000000 --- a/include/float_utils.h +++ /dev/null @@ -1,533 +0,0 @@ -// Copyright (c) 2024, ARM Limited. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -#ifndef TOSA_FLOAT_UTILS_H_ -#define TOSA_FLOAT_UTILS_H_ - -#include <algorithm> -#include <cstdint> -#include <limits> -#include <type_traits> -#if defined(__cpp_lib_bit_cast) -#include <bit> -#endif // defined(__cpp_lib_bit_cast) - -namespace tosa -{ - -namespace float_support -{ - -struct hidden -{}; - -#if defined(__cpp_lib_bit_cast) -#define BITCAST_CONSTEXPR constexpr inline - -constexpr inline int32_t get_bits(const float& f) -{ - return std::bit_cast<int32_t>(f); -} -constexpr inline float from_bits(const int32_t& i) -{ - return std::bit_cast<float>(i); -} - -#else -#define BITCAST_CONSTEXPR inline - -union ufloat32 -{ - constexpr ufloat32(const float& x) - : f(x) - {} - constexpr ufloat32(const int32_t& x) - : i(x) - {} - - float f; - int32_t i; -}; - -inline int32_t get_bits(const float& f) -{ - return ufloat32(f).i; -} -inline float from_bits(const int32_t& i) -{ - return ufloat32(i).f; -} -#endif - -} // namespace float_support - -template <typename storage_t, - size_t n_exp_bits, - bool has_nan, - bool with_denorm, - bool with_infinity, - std::enable_if_t<(n_exp_bits + 1 < sizeof(storage_t) * 8), bool> = true> -class float_t -{ - storage_t m_data = 0; - -public: - static constexpr size_t n_exponent_bits = n_exp_bits; - static constexpr size_t n_significand_bits = sizeof(storage_t) * 8 - 1 - n_exp_bits; - static constexpr int64_t exponent_bias = (1 << (n_exp_bits - 1)) - 1; - - /// \brief Construct a floating point type with the given bit - /// representation. - static constexpr float_t from_bits(storage_t bits) - { - return float_t(float_support::hidden(), bits); - } - - /// \brief Construct a float from the given sign, exponent and significand - /// bits. - static constexpr float_t from_bits(bool pm, storage_t e, storage_t s) - { - storage_t bits = pm ? 1 : 0; - - bits <<= n_exp_bits; - bits |= e; - - bits <<= n_significand_bits; - if (with_denorm || e) - bits |= s; - - return float_t(float_support::hidden(), bits); - } - - /// \brief (Hidden) Construct a float type from a given bit pattern - constexpr float_t(const float_support::hidden&, storage_t bits) - : m_data(bits) - {} - - constexpr float_t() - : m_data(0) - {} - constexpr float_t(const float_t& other) - : m_data(other.m_data) - {} - - /// \brief Cast to a different floating point representation. - template <typename other_storage_t, - size_t other_n_exp_bits, - bool other_has_nan, - bool other_has_denorm, - bool other_has_infinity> - constexpr inline - operator float_t<other_storage_t, other_n_exp_bits, other_has_nan, other_has_denorm, other_has_infinity>() const - { - using other_float_t = - float_t<other_storage_t, other_n_exp_bits, other_has_nan, other_has_denorm, other_has_infinity>; - - // Shortcut for types which are fundamentally similar (e.g., bf16 -> - // fp32) - if constexpr (n_exp_bits == other_n_exp_bits && sizeof(other_storage_t) >= sizeof(storage_t) && - has_nan == other_has_nan) - { - return other_float_t::from_bits(static_cast<other_storage_t>(m_data) - << (sizeof(other_storage_t) - sizeof(storage_t)) * 8); - } - - // Get initial values for the new floating point type - const bool sign_bit = m_data < 0; - int64_t new_exponent_bits = 0; - uint64_t new_significand = 0; - - if (is_nan() || is_infinity()) - { - new_exponent_bits = (1 << other_n_exp_bits) - 1; - - if (is_nan()) - { - if constexpr (other_has_infinity) - { - // Copy across the `not_quiet bit`; set the LSB. Don't - // attempt to copy across any of the rest of the payload. - new_significand = - 0x1 | (((significand() >> (n_significand_bits - 1)) & 1) << other_float_t::n_significand_bits); - } - else - { - new_significand = (1ul << other_float_t::n_significand_bits) - 1; - } - } - else if constexpr (!other_has_infinity) - { - new_significand = (1ul << other_float_t::n_significand_bits) - (other_has_nan ? 2 : 1); - } - } - else if (!is_zero()) - { - const int64_t this_exponent_bits = exponent_bits(); - { - constexpr int64_t exponent_rebias = other_float_t::exponent_bias - exponent_bias; - new_exponent_bits = std::max(this_exponent_bits + exponent_rebias, exponent_rebias + 1); - } - new_significand = this->significand() << (64 - n_significand_bits); - - // Normalise subnormals - if (this_exponent_bits == 0) - { - // Shift the most-significant 1 out of the magnitude to convert - // it to a significand. Modify the exponent accordingly. - uint8_t shift = __builtin_clzl(new_significand) + 1; - new_exponent_bits -= shift; - new_significand <<= shift; - } - - // Align the significand for the output type - uint32_t shift = 64 - other_float_t::n_significand_bits; - const bool other_is_subnormal = new_exponent_bits <= 0; - if (other_is_subnormal) - { - shift += 1 - new_exponent_bits; - new_exponent_bits = 0; - } - - const uint64_t shift_out = shift == 64 ? new_significand : new_significand & ((1ll << shift) - 1); - new_significand = shift == 64 ? 0 : new_significand >> shift; - - // Reinsert the most-significant-one if this is a subnormal in the - // output type. - new_significand |= (other_is_subnormal ? 1ll : 0) << (64 - shift); - - // Apply rounding based on the bits shifted out of the significand - const uint64_t shift_half = 1ll << (shift - 1); - if (shift_out > shift_half || (shift_out == shift_half && (new_significand & 1))) - { - new_significand += 1; - - // Handle the case that the significand overflowed due to - // rounding - constexpr uint64_t max_significand = (1ll << other_float_t::n_significand_bits) - 1; - if (new_significand > max_significand) - { - new_significand = 0; - new_exponent_bits++; - } - } - - // Saturate to infinity if the exponent is larger than can be - // represented in the output type. This can only occur if the size - // of the exponent of the new type is not greater than the exponent - // of the old type. - if constexpr (other_n_exp_bits <= n_exp_bits) - { - constexpr int64_t inf_exp_bits = (1ll << other_n_exp_bits) - 1; - if (new_exponent_bits >= inf_exp_bits) - { - new_exponent_bits = inf_exp_bits; - new_significand = - other_has_infinity ? 0 : (1ul << other_float_t::n_significand_bits) - (other_has_nan ? 2 : 1); - } - } - } - - return other_float_t::from_bits(sign_bit, new_exponent_bits, new_significand); - } - - /// \brief Convert from a 32-bit floating point value - BITCAST_CONSTEXPR - float_t(const float& f) - { - // If this format exactly represents the binary32 format then get - // the bits from the provided float; otherwise get a binary32 - // representation and then convert to this format. - if constexpr (represents_binary32()) - m_data = float_support::get_bits(f); - else - m_data = static_cast<float_t<storage_t, n_exp_bits, has_nan, with_denorm, with_infinity>>( - static_cast<float_t<int32_t, 8, true, true, true>>(f)) - .m_data; - } - - /// \brief Cast to a 32-bit floating point value - BITCAST_CONSTEXPR operator float() const - { - // If this format exactly represents the binary32 format then return - // a float; otherwise get a binary32 representation and then return - // a float. - if constexpr (represents_binary32()) - return float_support::from_bits(m_data); - else - return static_cast<float>(this->operator float_t<int32_t, 8, true, true, true>()); - } - - /// \brief Return whether this type represents the IEEE754 binary32 - /// format - constexpr static inline bool represents_binary32() - { - return std::is_same_v<storage_t, int32_t> && n_exp_bits == 8 && has_nan && with_denorm && with_infinity; - } - - constexpr auto operator-() const - { - return from_bits(m_data ^ (1ll << (sizeof(storage_t) * 8 - 1))); - } - - constexpr bool is_subnormal() const - { - return exponent_bits() == 0 && significand() != 0; - } - - constexpr bool is_zero() const - { - return exponent_bits() == 0 && significand() == 0; - } - - constexpr bool is_nan() const - { - return has_nan && (exponent_bits() == (1ul << n_exponent_bits) - 1) && - ((with_infinity && significand()) || - (!with_infinity && significand() == (1ul << n_significand_bits) - 1)); - } - - constexpr bool is_infinity() const - { - return with_infinity && ((exponent_bits() == (1ul << n_exponent_bits) - 1) && !significand()); - } - - constexpr inline const storage_t& bits() const - { - return m_data; - } - - /// \brief Get the exponent - constexpr inline int64_t exponent() const - { - return std::max<int64_t>(exponent_bits(), 1ul) - exponent_bias; - } - - /// \brief Get the bits from the exponent - constexpr inline uint64_t exponent_bits() const - { - constexpr uint64_t mask = (1ul << n_exp_bits) - 1; - return (m_data >> n_significand_bits) & mask; - } - - constexpr inline uint64_t significand() const - { - return m_data & ((1ul << n_significand_bits) - 1); - } - - constexpr inline bool operator==(const float_t& other) const - { - return !is_nan() && !other.is_nan() && ((is_zero() && other.is_zero()) || bits() == other.bits()); - } - - constexpr inline float_t& operator+=(const float_t& rhs) - { - this->m_data = static_cast<float_t>(static_cast<float>(*this) + static_cast<float>(rhs)).bits(); - return *this; - } -}; - -// This should probably be exported so we can use it elsewhere -#undef BITCAST_CONSTEXPR - -namespace float_support -{ - -// Pre-C++23 these can't be computed as constexpr, so have to hardcode them - -template <int> -struct digits10; // floor(log10(2) * (digits - 1) -template <int> -struct max_digits10; // ceil(log10(2) * digits + 1) -template <int> -struct min_exponent10; // floor(log10(2) * min_exponent) -template <int> -struct max_exponent10; // floor(log10(2) * max_exponent) - -template <> -struct digits10<8> -{ - constexpr static inline int value = 2; -}; - -template <> -struct max_digits10<8> -{ - constexpr static inline int value = 4; -}; - -template <> -struct digits10<10> -{ - constexpr static inline int value = 2; -}; - -template <> -struct max_digits10<10> -{ - constexpr static inline int value = 5; -}; - -template <> -struct digits10<24> -{ - constexpr static inline int value = 6; -}; - -template <> -struct max_digits10<24> -{ - constexpr static inline int value = 9; -}; - -template <> -struct min_exponent10<-13> -{ - constexpr static inline int value = -3; -}; - -template <> -struct max_exponent10<16> -{ - constexpr static inline int value = 4; -}; - -template <> -struct min_exponent10<-125> -{ - constexpr static inline int value = -37; -}; - -template <> -struct max_exponent10<128> -{ - constexpr static inline int value = 38; -}; - -template <int d> -inline constexpr int digits10_v = digits10<d>::value; -template <int d> -inline constexpr int max_digits10_v = max_digits10<d>::value; - -template <int e> -inline constexpr int min_exponent10_v = min_exponent10<e>::value; - -template <int e> -inline constexpr int max_exponent10_v = max_exponent10<e>::value; - -} // namespace float_support - -} // namespace tosa - -namespace std -{ - -template <typename storage_t, size_t n_exp_bits, bool has_nan, bool has_denorm, bool has_inf> -struct is_floating_point<tosa::float_t<storage_t, n_exp_bits, has_nan, has_denorm, has_inf>> - : std::integral_constant<bool, true> -{}; - -template <typename storage_t, size_t n_exp_bits, bool has_nan, bool with_denorm, bool with_inf> -class numeric_limits<tosa::float_t<storage_t, n_exp_bits, has_nan, with_denorm, with_inf>> -{ - using this_float_t = tosa::float_t<storage_t, n_exp_bits, has_nan, with_denorm, with_inf>; - -public: - static constexpr bool is_specialized = true; - - static constexpr auto min() noexcept - { - return this_float_t::from_bits(false, 1, 0); - } - - static constexpr auto max() noexcept - { - return this_float_t::from_bits(false, (1 << this_float_t::n_exponent_bits) - 2, - (1 << this_float_t::n_significand_bits) - 1); - } - - static constexpr auto lowest() noexcept - { - return -max(); - } - - static constexpr int digits = this_float_t::n_significand_bits + 1; - static constexpr int digits10 = tosa::float_support::digits10_v<digits>; - static constexpr int max_digits10 = tosa::float_support::max_digits10_v<digits>; - - static constexpr bool is_signed = true; - static constexpr bool is_integer = false; - static constexpr bool is_exact = false; - static constexpr int radix = 2; - - static constexpr auto epsilon() noexcept - { - return this_float_t::from_bits(false, this_float_t::exponent_bias - this_float_t::n_significand_bits, 0); - } - - static constexpr auto round_error() noexcept - { - return this_float_t::from_bits(0, this_float_t::exponent_bias - 1, 0); - } - - static constexpr int min_exponent = (1 - this_float_t::exponent_bias) + 1; - static constexpr int min_exponent10 = tosa::float_support::min_exponent10_v<min_exponent>; - static constexpr int max_exponent = this_float_t::exponent_bias + 1; - static constexpr int max_exponent10 = tosa::float_support::max_exponent10_v<max_exponent>; - - static constexpr bool has_infinity = with_inf; - static constexpr bool has_quiet_NaN = has_nan; - static constexpr bool has_signaling_NaN = true; - static constexpr float_denorm_style has_denorm = with_denorm ? denorm_present : denorm_absent; - static constexpr bool has_denorm_loss = false; - - static constexpr auto infinity() noexcept - { - if constexpr (with_inf) - { - return this_float_t::from_bits(false, (1 << this_float_t::n_exponent_bits) - 1, 0); - } - else - { - return this_float_t::from_bits(false, 0, 0); - } - } - - static constexpr auto quiet_NaN() noexcept - { - return this_float_t::from_bits(false, (1 << this_float_t::n_exponent_bits) - 1, - 1 << (this_float_t::n_significand_bits - 1) | 1); - } - - static constexpr auto signaling_NaN() noexcept - { - return this_float_t::from_bits(false, (1 << this_float_t::n_exponent_bits) - 1, 1); - } - - static constexpr auto denorm_min() noexcept - { - return this_float_t::from_bits(false, 0, 1); - } - - static constexpr bool is_iec559 = false; - static constexpr bool is_bounded = false; - static constexpr bool is_modulo = false; - - static constexpr bool traps = false; - static constexpr bool tinyness_before = false; - static constexpr float_round_style round_style = round_to_nearest; -}; - -} // namespace std - -#endif // TOSA_FLOAT_UTILS_H_ |