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Diffstat (limited to 'thirdparty/glslang/SPIRV/hex_float.h')
| -rw-r--r-- | thirdparty/glslang/SPIRV/hex_float.h | 1078 |
1 files changed, 1078 insertions, 0 deletions
diff --git a/thirdparty/glslang/SPIRV/hex_float.h b/thirdparty/glslang/SPIRV/hex_float.h new file mode 100644 index 0000000000..905b21a45a --- /dev/null +++ b/thirdparty/glslang/SPIRV/hex_float.h @@ -0,0 +1,1078 @@ +// Copyright (c) 2015-2016 The Khronos Group Inc. +// +// 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 LIBSPIRV_UTIL_HEX_FLOAT_H_ +#define LIBSPIRV_UTIL_HEX_FLOAT_H_ + +#include <cassert> +#include <cctype> +#include <cmath> +#include <cstdint> +#include <iomanip> +#include <limits> +#include <sstream> + +#if defined(_MSC_VER) && _MSC_VER < 1800 +namespace std { +bool isnan(double f) +{ + return ::_isnan(f) != 0; +} +bool isinf(double f) +{ + return ::_finite(f) == 0; +} +} +#endif + +#include "bitutils.h" + +namespace spvutils { + +class Float16 { + public: + Float16(uint16_t v) : val(v) {} + Float16() {} + static bool isNan(const Float16& val) { + return ((val.val & 0x7C00) == 0x7C00) && ((val.val & 0x3FF) != 0); + } + // Returns true if the given value is any kind of infinity. + static bool isInfinity(const Float16& val) { + return ((val.val & 0x7C00) == 0x7C00) && ((val.val & 0x3FF) == 0); + } + Float16(const Float16& other) { val = other.val; } + uint16_t get_value() const { return val; } + + // Returns the maximum normal value. + static Float16 max() { return Float16(0x7bff); } + // Returns the lowest normal value. + static Float16 lowest() { return Float16(0xfbff); } + + private: + uint16_t val; +}; + +// To specialize this type, you must override uint_type to define +// an unsigned integer that can fit your floating point type. +// You must also add a isNan function that returns true if +// a value is Nan. +template <typename T> +struct FloatProxyTraits { + typedef void uint_type; +}; + +template <> +struct FloatProxyTraits<float> { + typedef uint32_t uint_type; + static bool isNan(float f) { return std::isnan(f); } + // Returns true if the given value is any kind of infinity. + static bool isInfinity(float f) { return std::isinf(f); } + // Returns the maximum normal value. + static float max() { return std::numeric_limits<float>::max(); } + // Returns the lowest normal value. + static float lowest() { return std::numeric_limits<float>::lowest(); } +}; + +template <> +struct FloatProxyTraits<double> { + typedef uint64_t uint_type; + static bool isNan(double f) { return std::isnan(f); } + // Returns true if the given value is any kind of infinity. + static bool isInfinity(double f) { return std::isinf(f); } + // Returns the maximum normal value. + static double max() { return std::numeric_limits<double>::max(); } + // Returns the lowest normal value. + static double lowest() { return std::numeric_limits<double>::lowest(); } +}; + +template <> +struct FloatProxyTraits<Float16> { + typedef uint16_t uint_type; + static bool isNan(Float16 f) { return Float16::isNan(f); } + // Returns true if the given value is any kind of infinity. + static bool isInfinity(Float16 f) { return Float16::isInfinity(f); } + // Returns the maximum normal value. + static Float16 max() { return Float16::max(); } + // Returns the lowest normal value. + static Float16 lowest() { return Float16::lowest(); } +}; + +// Since copying a floating point number (especially if it is NaN) +// does not guarantee that bits are preserved, this class lets us +// store the type and use it as a float when necessary. +template <typename T> +class FloatProxy { + public: + typedef typename FloatProxyTraits<T>::uint_type uint_type; + + // Since this is to act similar to the normal floats, + // do not initialize the data by default. + FloatProxy() {} + + // Intentionally non-explicit. This is a proxy type so + // implicit conversions allow us to use it more transparently. + FloatProxy(T val) { data_ = BitwiseCast<uint_type>(val); } + + // Intentionally non-explicit. This is a proxy type so + // implicit conversions allow us to use it more transparently. + FloatProxy(uint_type val) { data_ = val; } + + // This is helpful to have and is guaranteed not to stomp bits. + FloatProxy<T> operator-() const { + return static_cast<uint_type>(data_ ^ + (uint_type(0x1) << (sizeof(T) * 8 - 1))); + } + + // Returns the data as a floating point value. + T getAsFloat() const { return BitwiseCast<T>(data_); } + + // Returns the raw data. + uint_type data() const { return data_; } + + // Returns true if the value represents any type of NaN. + bool isNan() { return FloatProxyTraits<T>::isNan(getAsFloat()); } + // Returns true if the value represents any type of infinity. + bool isInfinity() { return FloatProxyTraits<T>::isInfinity(getAsFloat()); } + + // Returns the maximum normal value. + static FloatProxy<T> max() { + return FloatProxy<T>(FloatProxyTraits<T>::max()); + } + // Returns the lowest normal value. + static FloatProxy<T> lowest() { + return FloatProxy<T>(FloatProxyTraits<T>::lowest()); + } + + private: + uint_type data_; +}; + +template <typename T> +bool operator==(const FloatProxy<T>& first, const FloatProxy<T>& second) { + return first.data() == second.data(); +} + +// Reads a FloatProxy value as a normal float from a stream. +template <typename T> +std::istream& operator>>(std::istream& is, FloatProxy<T>& value) { + T float_val; + is >> float_val; + value = FloatProxy<T>(float_val); + return is; +} + +// This is an example traits. It is not meant to be used in practice, but will +// be the default for any non-specialized type. +template <typename T> +struct HexFloatTraits { + // Integer type that can store this hex-float. + typedef void uint_type; + // Signed integer type that can store this hex-float. + typedef void int_type; + // The numerical type that this HexFloat represents. + typedef void underlying_type; + // The type needed to construct the underlying type. + typedef void native_type; + // The number of bits that are actually relevant in the uint_type. + // This allows us to deal with, for example, 24-bit values in a 32-bit + // integer. + static const uint32_t num_used_bits = 0; + // Number of bits that represent the exponent. + static const uint32_t num_exponent_bits = 0; + // Number of bits that represent the fractional part. + static const uint32_t num_fraction_bits = 0; + // The bias of the exponent. (How much we need to subtract from the stored + // value to get the correct value.) + static const uint32_t exponent_bias = 0; +}; + +// Traits for IEEE float. +// 1 sign bit, 8 exponent bits, 23 fractional bits. +template <> +struct HexFloatTraits<FloatProxy<float>> { + typedef uint32_t uint_type; + typedef int32_t int_type; + typedef FloatProxy<float> underlying_type; + typedef float native_type; + static const uint_type num_used_bits = 32; + static const uint_type num_exponent_bits = 8; + static const uint_type num_fraction_bits = 23; + static const uint_type exponent_bias = 127; +}; + +// Traits for IEEE double. +// 1 sign bit, 11 exponent bits, 52 fractional bits. +template <> +struct HexFloatTraits<FloatProxy<double>> { + typedef uint64_t uint_type; + typedef int64_t int_type; + typedef FloatProxy<double> underlying_type; + typedef double native_type; + static const uint_type num_used_bits = 64; + static const uint_type num_exponent_bits = 11; + static const uint_type num_fraction_bits = 52; + static const uint_type exponent_bias = 1023; +}; + +// Traits for IEEE half. +// 1 sign bit, 5 exponent bits, 10 fractional bits. +template <> +struct HexFloatTraits<FloatProxy<Float16>> { + typedef uint16_t uint_type; + typedef int16_t int_type; + typedef uint16_t underlying_type; + typedef uint16_t native_type; + static const uint_type num_used_bits = 16; + static const uint_type num_exponent_bits = 5; + static const uint_type num_fraction_bits = 10; + static const uint_type exponent_bias = 15; +}; + +enum round_direction { + kRoundToZero, + kRoundToNearestEven, + kRoundToPositiveInfinity, + kRoundToNegativeInfinity +}; + +// Template class that houses a floating pointer number. +// It exposes a number of constants based on the provided traits to +// assist in interpreting the bits of the value. +template <typename T, typename Traits = HexFloatTraits<T>> +class HexFloat { + public: + typedef typename Traits::uint_type uint_type; + typedef typename Traits::int_type int_type; + typedef typename Traits::underlying_type underlying_type; + typedef typename Traits::native_type native_type; + + explicit HexFloat(T f) : value_(f) {} + + T value() const { return value_; } + void set_value(T f) { value_ = f; } + + // These are all written like this because it is convenient to have + // compile-time constants for all of these values. + + // Pass-through values to save typing. + static const uint32_t num_used_bits = Traits::num_used_bits; + static const uint32_t exponent_bias = Traits::exponent_bias; + static const uint32_t num_exponent_bits = Traits::num_exponent_bits; + static const uint32_t num_fraction_bits = Traits::num_fraction_bits; + + // Number of bits to shift left to set the highest relevant bit. + static const uint32_t top_bit_left_shift = num_used_bits - 1; + // How many nibbles (hex characters) the fractional part takes up. + static const uint32_t fraction_nibbles = (num_fraction_bits + 3) / 4; + // If the fractional part does not fit evenly into a hex character (4-bits) + // then we have to left-shift to get rid of leading 0s. This is the amount + // we have to shift (might be 0). + static const uint32_t num_overflow_bits = + fraction_nibbles * 4 - num_fraction_bits; + + // The representation of the fraction, not the actual bits. This + // includes the leading bit that is usually implicit. + static const uint_type fraction_represent_mask = + spvutils::SetBits<uint_type, 0, + num_fraction_bits + num_overflow_bits>::get; + + // The topmost bit in the nibble-aligned fraction. + static const uint_type fraction_top_bit = + uint_type(1) << (num_fraction_bits + num_overflow_bits - 1); + + // The least significant bit in the exponent, which is also the bit + // immediately to the left of the significand. + static const uint_type first_exponent_bit = uint_type(1) + << (num_fraction_bits); + + // The mask for the encoded fraction. It does not include the + // implicit bit. + static const uint_type fraction_encode_mask = + spvutils::SetBits<uint_type, 0, num_fraction_bits>::get; + + // The bit that is used as a sign. + static const uint_type sign_mask = uint_type(1) << top_bit_left_shift; + + // The bits that represent the exponent. + static const uint_type exponent_mask = + spvutils::SetBits<uint_type, num_fraction_bits, num_exponent_bits>::get; + + // How far left the exponent is shifted. + static const uint32_t exponent_left_shift = num_fraction_bits; + + // How far from the right edge the fraction is shifted. + static const uint32_t fraction_right_shift = + static_cast<uint32_t>(sizeof(uint_type) * 8) - num_fraction_bits; + + // The maximum representable unbiased exponent. + static const int_type max_exponent = + (exponent_mask >> num_fraction_bits) - exponent_bias; + // The minimum representable exponent for normalized numbers. + static const int_type min_exponent = -static_cast<int_type>(exponent_bias); + + // Returns the bits associated with the value. + uint_type getBits() const { return spvutils::BitwiseCast<uint_type>(value_); } + + // Returns the bits associated with the value, without the leading sign bit. + uint_type getUnsignedBits() const { + return static_cast<uint_type>(spvutils::BitwiseCast<uint_type>(value_) & + ~sign_mask); + } + + // Returns the bits associated with the exponent, shifted to start at the + // lsb of the type. + const uint_type getExponentBits() const { + return static_cast<uint_type>((getBits() & exponent_mask) >> + num_fraction_bits); + } + + // Returns the exponent in unbiased form. This is the exponent in the + // human-friendly form. + const int_type getUnbiasedExponent() const { + return static_cast<int_type>(getExponentBits() - exponent_bias); + } + + // Returns just the significand bits from the value. + const uint_type getSignificandBits() const { + return getBits() & fraction_encode_mask; + } + + // If the number was normalized, returns the unbiased exponent. + // If the number was denormal, normalize the exponent first. + const int_type getUnbiasedNormalizedExponent() const { + if ((getBits() & ~sign_mask) == 0) { // special case if everything is 0 + return 0; + } + int_type exp = getUnbiasedExponent(); + if (exp == min_exponent) { // We are in denorm land. + uint_type significand_bits = getSignificandBits(); + while ((significand_bits & (first_exponent_bit >> 1)) == 0) { + significand_bits = static_cast<uint_type>(significand_bits << 1); + exp = static_cast<int_type>(exp - 1); + } + significand_bits &= fraction_encode_mask; + } + return exp; + } + + // Returns the signficand after it has been normalized. + const uint_type getNormalizedSignificand() const { + int_type unbiased_exponent = getUnbiasedNormalizedExponent(); + uint_type significand = getSignificandBits(); + for (int_type i = unbiased_exponent; i <= min_exponent; ++i) { + significand = static_cast<uint_type>(significand << 1); + } + significand &= fraction_encode_mask; + return significand; + } + + // Returns true if this number represents a negative value. + bool isNegative() const { return (getBits() & sign_mask) != 0; } + + // Sets this HexFloat from the individual components. + // Note this assumes EVERY significand is normalized, and has an implicit + // leading one. This means that the only way that this method will set 0, + // is if you set a number so denormalized that it underflows. + // Do not use this method with raw bits extracted from a subnormal number, + // since subnormals do not have an implicit leading 1 in the significand. + // The significand is also expected to be in the + // lowest-most num_fraction_bits of the uint_type. + // The exponent is expected to be unbiased, meaning an exponent of + // 0 actually means 0. + // If underflow_round_up is set, then on underflow, if a number is non-0 + // and would underflow, we round up to the smallest denorm. + void setFromSignUnbiasedExponentAndNormalizedSignificand( + bool negative, int_type exponent, uint_type significand, + bool round_denorm_up) { + bool significand_is_zero = significand == 0; + + if (exponent <= min_exponent) { + // If this was denormalized, then we have to shift the bit on, meaning + // the significand is not zero. + significand_is_zero = false; + significand |= first_exponent_bit; + significand = static_cast<uint_type>(significand >> 1); + } + + while (exponent < min_exponent) { + significand = static_cast<uint_type>(significand >> 1); + ++exponent; + } + + if (exponent == min_exponent) { + if (significand == 0 && !significand_is_zero && round_denorm_up) { + significand = static_cast<uint_type>(0x1); + } + } + + uint_type new_value = 0; + if (negative) { + new_value = static_cast<uint_type>(new_value | sign_mask); + } + exponent = static_cast<int_type>(exponent + exponent_bias); + assert(exponent >= 0); + + // put it all together + exponent = static_cast<uint_type>((exponent << exponent_left_shift) & + exponent_mask); + significand = static_cast<uint_type>(significand & fraction_encode_mask); + new_value = static_cast<uint_type>(new_value | (exponent | significand)); + value_ = BitwiseCast<T>(new_value); + } + + // Increments the significand of this number by the given amount. + // If this would spill the significand into the implicit bit, + // carry is set to true and the significand is shifted to fit into + // the correct location, otherwise carry is set to false. + // All significands and to_increment are assumed to be within the bounds + // for a valid significand. + static uint_type incrementSignificand(uint_type significand, + uint_type to_increment, bool* carry) { + significand = static_cast<uint_type>(significand + to_increment); + *carry = false; + if (significand & first_exponent_bit) { + *carry = true; + // The implicit 1-bit will have carried, so we should zero-out the + // top bit and shift back. + significand = static_cast<uint_type>(significand & ~first_exponent_bit); + significand = static_cast<uint_type>(significand >> 1); + } + return significand; + } + + // These exist because MSVC throws warnings on negative right-shifts + // even if they are not going to be executed. Eg: + // constant_number < 0? 0: constant_number + // These convert the negative left-shifts into right shifts. + + template <typename int_type> + uint_type negatable_left_shift(int_type N, uint_type val) + { + if(N >= 0) + return val << N; + + return val >> -N; + } + + template <typename int_type> + uint_type negatable_right_shift(int_type N, uint_type val) + { + if(N >= 0) + return val >> N; + + return val << -N; + } + + // Returns the significand, rounded to fit in a significand in + // other_T. This is shifted so that the most significant + // bit of the rounded number lines up with the most significant bit + // of the returned significand. + template <typename other_T> + typename other_T::uint_type getRoundedNormalizedSignificand( + round_direction dir, bool* carry_bit) { + typedef typename other_T::uint_type other_uint_type; + static const int_type num_throwaway_bits = + static_cast<int_type>(num_fraction_bits) - + static_cast<int_type>(other_T::num_fraction_bits); + + static const uint_type last_significant_bit = + (num_throwaway_bits < 0) + ? 0 + : negatable_left_shift(num_throwaway_bits, 1u); + static const uint_type first_rounded_bit = + (num_throwaway_bits < 1) + ? 0 + : negatable_left_shift(num_throwaway_bits - 1, 1u); + + static const uint_type throwaway_mask_bits = + num_throwaway_bits > 0 ? num_throwaway_bits : 0; + static const uint_type throwaway_mask = + spvutils::SetBits<uint_type, 0, throwaway_mask_bits>::get; + + *carry_bit = false; + other_uint_type out_val = 0; + uint_type significand = getNormalizedSignificand(); + // If we are up-casting, then we just have to shift to the right location. + if (num_throwaway_bits <= 0) { + out_val = static_cast<other_uint_type>(significand); + uint_type shift_amount = static_cast<uint_type>(-num_throwaway_bits); + out_val = static_cast<other_uint_type>(out_val << shift_amount); + return out_val; + } + + // If every non-representable bit is 0, then we don't have any casting to + // do. + if ((significand & throwaway_mask) == 0) { + return static_cast<other_uint_type>( + negatable_right_shift(num_throwaway_bits, significand)); + } + + bool round_away_from_zero = false; + // We actually have to narrow the significand here, so we have to follow the + // rounding rules. + switch (dir) { + case kRoundToZero: + break; + case kRoundToPositiveInfinity: + round_away_from_zero = !isNegative(); + break; + case kRoundToNegativeInfinity: + round_away_from_zero = isNegative(); + break; + case kRoundToNearestEven: + // Have to round down, round bit is 0 + if ((first_rounded_bit & significand) == 0) { + break; + } + if (((significand & throwaway_mask) & ~first_rounded_bit) != 0) { + // If any subsequent bit of the rounded portion is non-0 then we round + // up. + round_away_from_zero = true; + break; + } + // We are exactly half-way between 2 numbers, pick even. + if ((significand & last_significant_bit) != 0) { + // 1 for our last bit, round up. + round_away_from_zero = true; + break; + } + break; + } + + if (round_away_from_zero) { + return static_cast<other_uint_type>( + negatable_right_shift(num_throwaway_bits, incrementSignificand( + significand, last_significant_bit, carry_bit))); + } else { + return static_cast<other_uint_type>( + negatable_right_shift(num_throwaway_bits, significand)); + } + } + + // Casts this value to another HexFloat. If the cast is widening, + // then round_dir is ignored. If the cast is narrowing, then + // the result is rounded in the direction specified. + // This number will retain Nan and Inf values. + // It will also saturate to Inf if the number overflows, and + // underflow to (0 or min depending on rounding) if the number underflows. + template <typename other_T> + void castTo(other_T& other, round_direction round_dir) { + other = other_T(static_cast<typename other_T::native_type>(0)); + bool negate = isNegative(); + if (getUnsignedBits() == 0) { + if (negate) { + other.set_value(-other.value()); + } + return; + } + uint_type significand = getSignificandBits(); + bool carried = false; + typename other_T::uint_type rounded_significand = + getRoundedNormalizedSignificand<other_T>(round_dir, &carried); + + int_type exponent = getUnbiasedExponent(); + if (exponent == min_exponent) { + // If we are denormal, normalize the exponent, so that we can encode + // easily. + exponent = static_cast<int_type>(exponent + 1); + for (uint_type check_bit = first_exponent_bit >> 1; check_bit != 0; + check_bit = static_cast<uint_type>(check_bit >> 1)) { + exponent = static_cast<int_type>(exponent - 1); + if (check_bit & significand) break; + } + } + + bool is_nan = + (getBits() & exponent_mask) == exponent_mask && significand != 0; + bool is_inf = + !is_nan && + ((exponent + carried) > static_cast<int_type>(other_T::exponent_bias) || + (significand == 0 && (getBits() & exponent_mask) == exponent_mask)); + + // If we are Nan or Inf we should pass that through. + if (is_inf) { + other.set_value(BitwiseCast<typename other_T::underlying_type>( + static_cast<typename other_T::uint_type>( + (negate ? other_T::sign_mask : 0) | other_T::exponent_mask))); + return; + } + if (is_nan) { + typename other_T::uint_type shifted_significand; + shifted_significand = static_cast<typename other_T::uint_type>( + negatable_left_shift( + static_cast<int_type>(other_T::num_fraction_bits) - + static_cast<int_type>(num_fraction_bits), significand)); + + // We are some sort of Nan. We try to keep the bit-pattern of the Nan + // as close as possible. If we had to shift off bits so we are 0, then we + // just set the last bit. + other.set_value(BitwiseCast<typename other_T::underlying_type>( + static_cast<typename other_T::uint_type>( + (negate ? other_T::sign_mask : 0) | other_T::exponent_mask | + (shifted_significand == 0 ? 0x1 : shifted_significand)))); + return; + } + + bool round_underflow_up = + isNegative() ? round_dir == kRoundToNegativeInfinity + : round_dir == kRoundToPositiveInfinity; + typedef typename other_T::int_type other_int_type; + // setFromSignUnbiasedExponentAndNormalizedSignificand will + // zero out any underflowing value (but retain the sign). + other.setFromSignUnbiasedExponentAndNormalizedSignificand( + negate, static_cast<other_int_type>(exponent), rounded_significand, + round_underflow_up); + return; + } + + private: + T value_; + + static_assert(num_used_bits == + Traits::num_exponent_bits + Traits::num_fraction_bits + 1, + "The number of bits do not fit"); + static_assert(sizeof(T) == sizeof(uint_type), "The type sizes do not match"); +}; + +// Returns 4 bits represented by the hex character. +inline uint8_t get_nibble_from_character(int character) { + const char* dec = "0123456789"; + const char* lower = "abcdef"; + const char* upper = "ABCDEF"; + const char* p = nullptr; + if ((p = strchr(dec, character))) { + return static_cast<uint8_t>(p - dec); + } else if ((p = strchr(lower, character))) { + return static_cast<uint8_t>(p - lower + 0xa); + } else if ((p = strchr(upper, character))) { + return static_cast<uint8_t>(p - upper + 0xa); + } + + assert(false && "This was called with a non-hex character"); + return 0; +} + +// Outputs the given HexFloat to the stream. +template <typename T, typename Traits> +std::ostream& operator<<(std::ostream& os, const HexFloat<T, Traits>& value) { + typedef HexFloat<T, Traits> HF; + typedef typename HF::uint_type uint_type; + typedef typename HF::int_type int_type; + + static_assert(HF::num_used_bits != 0, + "num_used_bits must be non-zero for a valid float"); + static_assert(HF::num_exponent_bits != 0, + "num_exponent_bits must be non-zero for a valid float"); + static_assert(HF::num_fraction_bits != 0, + "num_fractin_bits must be non-zero for a valid float"); + + const uint_type bits = spvutils::BitwiseCast<uint_type>(value.value()); + const char* const sign = (bits & HF::sign_mask) ? "-" : ""; + const uint_type exponent = static_cast<uint_type>( + (bits & HF::exponent_mask) >> HF::num_fraction_bits); + + uint_type fraction = static_cast<uint_type>((bits & HF::fraction_encode_mask) + << HF::num_overflow_bits); + + const bool is_zero = exponent == 0 && fraction == 0; + const bool is_denorm = exponent == 0 && !is_zero; + + // exponent contains the biased exponent we have to convert it back into + // the normal range. + int_type int_exponent = static_cast<int_type>(exponent - HF::exponent_bias); + // If the number is all zeros, then we actually have to NOT shift the + // exponent. + int_exponent = is_zero ? 0 : int_exponent; + + // If we are denorm, then start shifting, and decreasing the exponent until + // our leading bit is 1. + + if (is_denorm) { + while ((fraction & HF::fraction_top_bit) == 0) { + fraction = static_cast<uint_type>(fraction << 1); + int_exponent = static_cast<int_type>(int_exponent - 1); + } + // Since this is denormalized, we have to consume the leading 1 since it + // will end up being implicit. + fraction = static_cast<uint_type>(fraction << 1); // eat the leading 1 + fraction &= HF::fraction_represent_mask; + } + + uint_type fraction_nibbles = HF::fraction_nibbles; + // We do not have to display any trailing 0s, since this represents the + // fractional part. + while (fraction_nibbles > 0 && (fraction & 0xF) == 0) { + // Shift off any trailing values; + fraction = static_cast<uint_type>(fraction >> 4); + --fraction_nibbles; + } + + const auto saved_flags = os.flags(); + const auto saved_fill = os.fill(); + + os << sign << "0x" << (is_zero ? '0' : '1'); + if (fraction_nibbles) { + // Make sure to keep the leading 0s in place, since this is the fractional + // part. + os << "." << std::setw(static_cast<int>(fraction_nibbles)) + << std::setfill('0') << std::hex << fraction; + } + os << "p" << std::dec << (int_exponent >= 0 ? "+" : "") << int_exponent; + + os.flags(saved_flags); + os.fill(saved_fill); + + return os; +} + +// Returns true if negate_value is true and the next character on the +// input stream is a plus or minus sign. In that case we also set the fail bit +// on the stream and set the value to the zero value for its type. +template <typename T, typename Traits> +inline bool RejectParseDueToLeadingSign(std::istream& is, bool negate_value, + HexFloat<T, Traits>& value) { + if (negate_value) { + auto next_char = is.peek(); + if (next_char == '-' || next_char == '+') { + // Fail the parse. Emulate standard behaviour by setting the value to + // the zero value, and set the fail bit on the stream. + value = HexFloat<T, Traits>(typename HexFloat<T, Traits>::uint_type(0)); + is.setstate(std::ios_base::failbit); + return true; + } + } + return false; +} + +// Parses a floating point number from the given stream and stores it into the +// value parameter. +// If negate_value is true then the number may not have a leading minus or +// plus, and if it successfully parses, then the number is negated before +// being stored into the value parameter. +// If the value cannot be correctly parsed or overflows the target floating +// point type, then set the fail bit on the stream. +// TODO(dneto): Promise C++11 standard behavior in how the value is set in +// the error case, but only after all target platforms implement it correctly. +// In particular, the Microsoft C++ runtime appears to be out of spec. +template <typename T, typename Traits> +inline std::istream& ParseNormalFloat(std::istream& is, bool negate_value, + HexFloat<T, Traits>& value) { + if (RejectParseDueToLeadingSign(is, negate_value, value)) { + return is; + } + T val; + is >> val; + if (negate_value) { + val = -val; + } + value.set_value(val); + // In the failure case, map -0.0 to 0.0. + if (is.fail() && value.getUnsignedBits() == 0u) { + value = HexFloat<T, Traits>(typename HexFloat<T, Traits>::uint_type(0)); + } + if (val.isInfinity()) { + // Fail the parse. Emulate standard behaviour by setting the value to + // the closest normal value, and set the fail bit on the stream. + value.set_value((value.isNegative() | negate_value) ? T::lowest() + : T::max()); + is.setstate(std::ios_base::failbit); + } + return is; +} + +// Specialization of ParseNormalFloat for FloatProxy<Float16> values. +// This will parse the float as it were a 32-bit floating point number, +// and then round it down to fit into a Float16 value. +// The number is rounded towards zero. +// If negate_value is true then the number may not have a leading minus or +// plus, and if it successfully parses, then the number is negated before +// being stored into the value parameter. +// If the value cannot be correctly parsed or overflows the target floating +// point type, then set the fail bit on the stream. +// TODO(dneto): Promise C++11 standard behavior in how the value is set in +// the error case, but only after all target platforms implement it correctly. +// In particular, the Microsoft C++ runtime appears to be out of spec. +template <> +inline std::istream& +ParseNormalFloat<FloatProxy<Float16>, HexFloatTraits<FloatProxy<Float16>>>( + std::istream& is, bool negate_value, + HexFloat<FloatProxy<Float16>, HexFloatTraits<FloatProxy<Float16>>>& value) { + // First parse as a 32-bit float. + HexFloat<FloatProxy<float>> float_val(0.0f); + ParseNormalFloat(is, negate_value, float_val); + + // Then convert to 16-bit float, saturating at infinities, and + // rounding toward zero. + float_val.castTo(value, kRoundToZero); + + // Overflow on 16-bit behaves the same as for 32- and 64-bit: set the + // fail bit and set the lowest or highest value. + if (Float16::isInfinity(value.value().getAsFloat())) { + value.set_value(value.isNegative() ? Float16::lowest() : Float16::max()); + is.setstate(std::ios_base::failbit); + } + return is; +} + +// Reads a HexFloat from the given stream. +// If the float is not encoded as a hex-float then it will be parsed +// as a regular float. +// This may fail if your stream does not support at least one unget. +// Nan values can be encoded with "0x1.<not zero>p+exponent_bias". +// This would normally overflow a float and round to +// infinity but this special pattern is the exact representation for a NaN, +// and therefore is actually encoded as the correct NaN. To encode inf, +// either 0x0p+exponent_bias can be specified or any exponent greater than +// exponent_bias. +// Examples using IEEE 32-bit float encoding. +// 0x1.0p+128 (+inf) +// -0x1.0p-128 (-inf) +// +// 0x1.1p+128 (+Nan) +// -0x1.1p+128 (-Nan) +// +// 0x1p+129 (+inf) +// -0x1p+129 (-inf) +template <typename T, typename Traits> +std::istream& operator>>(std::istream& is, HexFloat<T, Traits>& value) { + using HF = HexFloat<T, Traits>; + using uint_type = typename HF::uint_type; + using int_type = typename HF::int_type; + + value.set_value(static_cast<typename HF::native_type>(0.f)); + + if (is.flags() & std::ios::skipws) { + // If the user wants to skip whitespace , then we should obey that. + while (std::isspace(is.peek())) { + is.get(); + } + } + + auto next_char = is.peek(); + bool negate_value = false; + + if (next_char != '-' && next_char != '0') { + return ParseNormalFloat(is, negate_value, value); + } + + if (next_char == '-') { + negate_value = true; + is.get(); + next_char = is.peek(); + } + + if (next_char == '0') { + is.get(); // We may have to unget this. + auto maybe_hex_start = is.peek(); + if (maybe_hex_start != 'x' && maybe_hex_start != 'X') { + is.unget(); + return ParseNormalFloat(is, negate_value, value); + } else { + is.get(); // Throw away the 'x'; + } + } else { + return ParseNormalFloat(is, negate_value, value); + } + + // This "looks" like a hex-float so treat it as one. + bool seen_p = false; + bool seen_dot = false; + uint_type fraction_index = 0; + + uint_type fraction = 0; + int_type exponent = HF::exponent_bias; + + // Strip off leading zeros so we don't have to special-case them later. + while ((next_char = is.peek()) == '0') { + is.get(); + } + + bool is_denorm = + true; // Assume denorm "representation" until we hear otherwise. + // NB: This does not mean the value is actually denorm, + // it just means that it was written 0. + bool bits_written = false; // Stays false until we write a bit. + while (!seen_p && !seen_dot) { + // Handle characters that are left of the fractional part. + if (next_char == '.') { + seen_dot = true; + } else if (next_char == 'p') { + seen_p = true; + } else if (::isxdigit(next_char)) { + // We know this is not denormalized since we have stripped all leading + // zeroes and we are not a ".". + is_denorm = false; + int number = get_nibble_from_character(next_char); + for (int i = 0; i < 4; ++i, number <<= 1) { + uint_type write_bit = (number & 0x8) ? 0x1 : 0x0; + if (bits_written) { + // If we are here the bits represented belong in the fractional + // part of the float, and we have to adjust the exponent accordingly. + fraction = static_cast<uint_type>( + fraction | + static_cast<uint_type>( + write_bit << (HF::top_bit_left_shift - fraction_index++))); + exponent = static_cast<int_type>(exponent + 1); + } + bits_written |= write_bit != 0; + } + } else { + // We have not found our exponent yet, so we have to fail. + is.setstate(std::ios::failbit); + return is; + } + is.get(); + next_char = is.peek(); + } + bits_written = false; + while (seen_dot && !seen_p) { + // Handle only fractional parts now. + if (next_char == 'p') { + seen_p = true; + } else if (::isxdigit(next_char)) { + int number = get_nibble_from_character(next_char); + for (int i = 0; i < 4; ++i, number <<= 1) { + uint_type write_bit = (number & 0x8) ? 0x01 : 0x00; + bits_written |= write_bit != 0; + if (is_denorm && !bits_written) { + // Handle modifying the exponent here this way we can handle + // an arbitrary number of hex values without overflowing our + // integer. + exponent = static_cast<int_type>(exponent - 1); + } else { + fraction = static_cast<uint_type>( + fraction | + static_cast<uint_type>( + write_bit << (HF::top_bit_left_shift - fraction_index++))); + } + } + } else { + // We still have not found our 'p' exponent yet, so this is not a valid + // hex-float. + is.setstate(std::ios::failbit); + return is; + } + is.get(); + next_char = is.peek(); + } + + bool seen_sign = false; + int8_t exponent_sign = 1; + int_type written_exponent = 0; + while (true) { + if ((next_char == '-' || next_char == '+')) { + if (seen_sign) { + is.setstate(std::ios::failbit); + return is; + } + seen_sign = true; + exponent_sign = (next_char == '-') ? -1 : 1; + } else if (::isdigit(next_char)) { + // Hex-floats express their exponent as decimal. + written_exponent = static_cast<int_type>(written_exponent * 10); + written_exponent = + static_cast<int_type>(written_exponent + (next_char - '0')); + } else { + break; + } + is.get(); + next_char = is.peek(); + } + + written_exponent = static_cast<int_type>(written_exponent * exponent_sign); + exponent = static_cast<int_type>(exponent + written_exponent); + + bool is_zero = is_denorm && (fraction == 0); + if (is_denorm && !is_zero) { + fraction = static_cast<uint_type>(fraction << 1); + exponent = static_cast<int_type>(exponent - 1); + } else if (is_zero) { + exponent = 0; + } + + if (exponent <= 0 && !is_zero) { + fraction = static_cast<uint_type>(fraction >> 1); + fraction |= static_cast<uint_type>(1) << HF::top_bit_left_shift; + } + + fraction = (fraction >> HF::fraction_right_shift) & HF::fraction_encode_mask; + + const int_type max_exponent = + SetBits<uint_type, 0, HF::num_exponent_bits>::get; + + // Handle actual denorm numbers + while (exponent < 0 && !is_zero) { + fraction = static_cast<uint_type>(fraction >> 1); + exponent = static_cast<int_type>(exponent + 1); + + fraction &= HF::fraction_encode_mask; + if (fraction == 0) { + // We have underflowed our fraction. We should clamp to zero. + is_zero = true; + exponent = 0; + } + } + + // We have overflowed so we should be inf/-inf. + if (exponent > max_exponent) { + exponent = max_exponent; + fraction = 0; + } + + uint_type output_bits = static_cast<uint_type>( + static_cast<uint_type>(negate_value ? 1 : 0) << HF::top_bit_left_shift); + output_bits |= fraction; + + uint_type shifted_exponent = static_cast<uint_type>( + static_cast<uint_type>(exponent << HF::exponent_left_shift) & + HF::exponent_mask); + output_bits |= shifted_exponent; + + T output_float = spvutils::BitwiseCast<T>(output_bits); + value.set_value(output_float); + + return is; +} + +// Writes a FloatProxy value to a stream. +// Zero and normal numbers are printed in the usual notation, but with +// enough digits to fully reproduce the value. Other values (subnormal, +// NaN, and infinity) are printed as a hex float. +template <typename T> +std::ostream& operator<<(std::ostream& os, const FloatProxy<T>& value) { + auto float_val = value.getAsFloat(); + switch (std::fpclassify(float_val)) { + case FP_ZERO: + case FP_NORMAL: { + auto saved_precision = os.precision(); + os.precision(std::numeric_limits<T>::digits10); + os << float_val; + os.precision(saved_precision); + } break; + default: + os << HexFloat<FloatProxy<T>>(value); + break; + } + return os; +} + +template <> +inline std::ostream& operator<<<Float16>(std::ostream& os, + const FloatProxy<Float16>& value) { + os << HexFloat<FloatProxy<Float16>>(value); + return os; +} +} + +#endif // LIBSPIRV_UTIL_HEX_FLOAT_H_ |