AK: Remove unused floating point conversion code
Currently I don't expect this code to be ever used in Ladybird.
This commit is contained in:
Jelle Raaijmakers
Andreas Kling
parent
69f11fc1c6
commit
f88acedc8f
Notes:
github-actions[bot]
2024-10-08 17:04:49 +00:00
Author: https://github.com/gmta Commit: https://github.com/LadybirdBrowser/ladybird/commit/f88acedc8f1 Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1682
4 changed files with 0 additions and 274 deletions
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@ -6,8 +6,6 @@
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#pragma once
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#include <AK/BitCast.h>
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#include <AK/StdLibExtras.h>
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#include <AK/Types.h>
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namespace AK {
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@ -125,193 +123,8 @@ union FloatExtractor<f32> {
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};
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static_assert(AssertSize<FloatExtractor<f32>, sizeof(f32)>());
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template<size_t S, size_t E, size_t M>
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requires(S <= 1 && E >= 1 && M >= 1 && (S + E + M) <= 64) class FloatingPointBits final {
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public:
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static size_t const signbit = S;
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static size_t const exponentbits = E;
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static size_t const mantissabits = M;
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template<typename T>
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requires(IsIntegral<T> && IsUnsigned<T> && sizeof(T) <= 8) constexpr FloatingPointBits(T bits)
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: m_bits(bits)
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{
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}
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constexpr FloatingPointBits(double value)
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: m_bits(bit_cast<u64>(value))
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{
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}
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constexpr FloatingPointBits(float value)
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: m_bits(bit_cast<u32>(value))
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{
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}
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double as_double() const
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requires(S == 1 && E == 11 && M == 52)
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{
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return bit_cast<double>(m_bits);
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}
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float as_float() const
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requires(S == 1 && E == 8 && M == 23)
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{
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return bit_cast<float>(static_cast<u32>(m_bits));
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}
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u64 bits() const { return m_bits; }
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private:
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u64 m_bits;
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};
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typedef FloatingPointBits<1, 8, 23> SingleFloatingPointBits;
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typedef FloatingPointBits<1, 11, 52> DoubleFloatingPointBits;
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/**
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* Convert between two IEEE 754 floating point types in any arrangement of sign, exponent and mantissa bits.
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*/
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template<typename To, typename From>
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constexpr To float_to_float(From const input)
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{
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constexpr u64 from_exponent_nonnumber = (1ull << From::exponentbits) - 1;
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constexpr u64 from_exponent_bias = (1ull << (From::exponentbits - 1)) - 1;
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constexpr u64 to_exponent_nonnumber = (1ull << To::exponentbits) - 1;
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constexpr u64 to_exponent_bias = (1ull << (To::exponentbits - 1)) - 1;
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constexpr u64 to_exponent_max = (1ull << To::exponentbits) - 2;
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// Deconstruct input bits to float components
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u64 from_sign = (input.bits() >> (From::exponentbits + From::mantissabits)) & From::signbit;
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u64 from_exponent = (input.bits() >> From::mantissabits) & ((1ull << From::exponentbits) - 1);
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u64 from_mantissa = input.bits() & ((1ull << From::mantissabits) - 1);
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u64 to_sign = from_sign & To::signbit;
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u64 to_exponent;
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u64 to_mantissa;
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auto target_value = [&to_sign, &to_exponent, &to_mantissa]() {
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return To((to_sign << (To::exponentbits + To::mantissabits)) | (to_exponent << To::mantissabits) | to_mantissa);
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};
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auto shift_mantissa = [](u64 mantissa) -> u64 {
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if constexpr (From::mantissabits < To::mantissabits)
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return mantissa << (To::mantissabits - From::mantissabits);
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else
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return mantissa >> (From::mantissabits - To::mantissabits);
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};
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// If target is unsigned and source is negative, clamp to 0 or keep NaN
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if constexpr (To::signbit == 0) {
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if (from_sign == 1) {
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if (from_exponent == from_exponent_nonnumber && from_mantissa > 0) {
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to_exponent = to_exponent_nonnumber;
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to_mantissa = 1;
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} else {
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to_exponent = 0;
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to_mantissa = 0;
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}
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return target_value();
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}
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}
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// If the source floating point is denormalized;
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if (from_exponent == 0) {
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// If the source mantissa is 0, the value is +/-0
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if (from_mantissa == 0) {
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to_exponent = 0;
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to_mantissa = 0;
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return target_value();
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}
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// If the source has more exponent bits than the target, then the largest possible
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// source mantissa still cannot be represented in the target denormalized value.
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if constexpr (From::exponentbits > To::exponentbits) {
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to_exponent = 0;
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to_mantissa = 0;
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return target_value();
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}
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// If the source and target have the same number of exponent bits, we only need to
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// shift the mantissa.
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if constexpr (From::exponentbits == To::exponentbits) {
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to_exponent = 0;
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to_mantissa = shift_mantissa(from_mantissa);
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return target_value();
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}
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// The target has more exponent bits, so our denormalized value can be represented
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// as a normalized value in the target floating point. Normalized values have an
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// implicit leading 1, so we shift the mantissa left until we find our explicit
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// leading 1 which is then dropped.
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int adjust_exponent = -1;
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to_mantissa = from_mantissa;
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do {
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++adjust_exponent;
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to_mantissa <<= 1;
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} while ((to_mantissa & (1ull << From::mantissabits)) == 0);
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to_exponent = to_exponent_bias - from_exponent_bias - adjust_exponent;
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// Drop the most significant bit from the mantissa
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to_mantissa &= (1ull << From::mantissabits) - 1;
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to_mantissa = shift_mantissa(to_mantissa);
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return target_value();
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}
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// If the source is NaN or +/-Inf, keep it that way
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if (from_exponent == from_exponent_nonnumber) {
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to_exponent = to_exponent_nonnumber;
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to_mantissa = (from_mantissa == 0) ? 0 : 1;
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return target_value();
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}
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// Determine the target exponent
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to_exponent = to_exponent_bias - from_exponent_bias + from_exponent;
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// If the calculated exponent exceeds the target's capacity, clamp both the exponent and the
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// mantissa to their maximum values.
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if (to_exponent > to_exponent_max) {
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to_exponent = to_exponent_max;
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to_mantissa = (1ull << To::mantissabits) - 1;
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return target_value();
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}
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// If the new exponent is less than 1, we can only represent this value as a denormalized number
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if (to_exponent < 1) {
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to_exponent = 0;
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// Add a leading 1 and shift the mantissa right
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int adjust_exponent = 1 - to_exponent_bias - from_exponent + from_exponent_bias;
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to_mantissa = ((1ull << From::mantissabits) | from_mantissa) >> adjust_exponent;
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to_mantissa = shift_mantissa(to_mantissa);
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return target_value();
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}
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// New exponent fits; shift the mantissa to fit as well
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to_mantissa = shift_mantissa(from_mantissa);
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return target_value();
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}
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template<typename O>
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constexpr O convert_from_native_double(double input) { return float_to_float<O>(DoubleFloatingPointBits(input)); }
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template<typename O>
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constexpr O convert_from_native_float(float input) { return float_to_float<O>(SingleFloatingPointBits(input)); }
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template<typename I>
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constexpr double convert_to_native_double(I input) { return float_to_float<DoubleFloatingPointBits>(input).as_double(); }
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template<typename I>
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constexpr float convert_to_native_float(I input) { return float_to_float<SingleFloatingPointBits>(input).as_float(); }
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}
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#if USING_AK_GLOBALLY
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using AK::DoubleFloatingPointBits;
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using AK::FloatExtractor;
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using AK::FloatingPointBits;
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using AK::SingleFloatingPointBits;
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using AK::convert_from_native_double;
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using AK::convert_from_native_float;
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using AK::convert_to_native_double;
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using AK::convert_to_native_float;
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using AK::float_to_float;
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#endif
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@ -28,7 +28,6 @@ tests = [
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"TestFind",
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"TestFixedArray",
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"TestFixedPoint",
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"TestFloatingPoint",
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"TestFloatingPointParsing",
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"TestFlyString",
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"TestFormat",
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@ -26,7 +26,6 @@ set(AK_TEST_SOURCES
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TestFind.cpp
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TestFixedArray.cpp
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TestFixedPoint.cpp
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TestFloatingPoint.cpp
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TestFloatingPointParsing.cpp
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TestFlyString.cpp
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TestFormat.cpp
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@ -1,85 +0,0 @@
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/*
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* Copyright (c) 2022, Jelle Raaijmakers <jelle@gmta.nl>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/FloatingPoint.h>
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#include <LibTest/TestCase.h>
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#include <math.h>
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TEST_CASE(f16_1_5_10_to_native_float)
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{
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auto within_approximate = [](u16 lhs, float rhs) -> bool {
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auto f32_lhs = convert_to_native_float(FloatingPointBits<1, 5, 10>(lhs));
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return fabsf(f32_lhs - rhs) <= 0.00001f;
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};
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EXPECT(within_approximate(0x0000, 0.f));
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EXPECT(within_approximate(0x03FF, 0.000061f));
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EXPECT(within_approximate(0x3CEF, 1.23339f));
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EXPECT(within_approximate(0xBC00, -1.f));
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EXPECT(within_approximate(0xA266, -0.0125f));
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float result;
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result = convert_to_native_float(FloatingPointBits<1, 5, 10>(0xFC01u));
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EXPECT(isnan(result));
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result = convert_to_native_float(FloatingPointBits<1, 5, 10>(0x7C00u));
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EXPECT(isinf(result));
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}
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TEST_CASE(float_to_double_roundtrips)
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{
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auto roundtrip = [](float floatvalue1) {
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auto doublevalue = convert_from_native_float<DoubleFloatingPointBits>(floatvalue1).as_double();
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auto floatbits = convert_from_native_double<SingleFloatingPointBits>(doublevalue);
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auto floatvalue2 = convert_to_native_float(floatbits);
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EXPECT_APPROXIMATE(floatvalue1, floatvalue2);
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};
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roundtrip(-1.0f);
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roundtrip(-0.1f);
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roundtrip(0.0f);
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roundtrip(0.000001f);
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roundtrip(0.1f);
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roundtrip(1.0f);
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roundtrip(3.141592f);
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roundtrip(16777216.0f);
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roundtrip(33554432.0f);
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roundtrip(1 / 0.0f);
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roundtrip(1 / -0.0f);
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roundtrip(0 / 0.0f);
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}
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TEST_CASE(normalize_denormalize)
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{
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// Go from denormalized float to normalized double
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auto denormalized_float = 6.709679e-39f;
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auto denormalized_float_bits = SingleFloatingPointBits(denormalized_float);
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auto normalized_double = convert_to_native_double(denormalized_float_bits);
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EXPECT_APPROXIMATE(denormalized_float, normalized_double);
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// Go back from normalized double to denormalized float
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auto normalized_double_bits = DoubleFloatingPointBits(normalized_double);
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auto reconstructed_denormalized_float = convert_to_native_float(normalized_double_bits);
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EXPECT_APPROXIMATE(denormalized_float, reconstructed_denormalized_float);
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}
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TEST_CASE(large_exponent)
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{
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// Make sure we support at least 62 bits of exponent
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auto large_exponent_float = convert_from_native_double<FloatingPointBits<1, 62, 1>>(1.0);
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auto converted_double = convert_to_native_double(large_exponent_float);
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EXPECT_APPROXIMATE(converted_double, 1.0);
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}
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TEST_CASE(large_mantissa)
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{
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// Make sure we support at least 62 bits of mantissa
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auto large_exponent_float = convert_from_native_double<FloatingPointBits<1, 1, 62>>(1.0);
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auto converted_double = convert_to_native_double(large_exponent_float);
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EXPECT_APPROXIMATE(converted_double, 1.0);
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}
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