fma.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2021 Tobias Hienzsch
 
#ifndef TETL_CMATH_FMA_HPP
#define TETL_CMATH_FMA_HPP
 
#include <etl/_config/all.hpp>
 
#include <etl/_type_traits/is_constant_evaluated.hpp>
#include <etl/_type_traits/is_same.hpp>
 
namespace etl {
 
namespace detail {
 
inline constexpr struct fma {
    template <typename Float>
    [[nodiscard]] constexpr auto operator()(Float x, Float y, Float z) const noexcept -> Float
    {
        if (not is_constant_evaluated()) {
#if __has_builtin(__builtin_fmaf)
            if constexpr (is_same_v<Float, float>) {
                return __builtin_fmaf(x, y, z);
            }
#endif
#if __has_builtin(__builtin_fma)
            if constexpr (is_same_v<Float, double>) {
                return __builtin_fma(x, y, z);
            }
#endif
        }
 
        return x * y + z;
    }
} fma;
 
} // namespace detail
 
/// \ingroup cmath
/// @{
 
/// Computes (x*y) + z as if to infinite precision and rounded only once to fit the result type.
/// \details https://en.cppreference.com/w/cpp/numeric/math/fma
/// \ingroup cmath
[[nodiscard]] constexpr auto fma(float x, float y, float z) noexcept -> float
{
    return etl::detail::fma(x, y, z);
}
[[nodiscard]] constexpr auto fmaf(float x, float y, float z) noexcept -> float
{
    return etl::detail::fma(x, y, z);
}
[[nodiscard]] constexpr auto fma(double x, double y, double z) noexcept -> double
{
    return etl::detail::fma(x, y, z);
}
[[nodiscard]] constexpr auto fma(long double x, long double y, long double z) noexcept -> long double
{
    return etl::detail::fma(x, y, z);
}
[[nodiscard]] constexpr auto fmal(long double x, long double y, long double z) noexcept -> long double
{
    return etl::detail::fma(x, y, z);
}
 
/// @}
 
} // namespace etl
 
#endif // TETL_CMATH_FMA_HPP