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#ifndef MIGRAPHX_FP8_IMPL_HPP
#define MIGRAPHX_FP8_IMPL_HPP

#define MIGRAPHX_CONST_FOLD(x) (__builtin_constant_p(x) ? (x) : (x))
namespace migraphx_f8_impl {
namespace detail {
template <bool B, class T, class F>
struct conditional
{
    using type = T;
};

template <class T, class F>
struct conditional<false, T, F>
{
    using type = F;
};

template <typename To, typename From>
inline constexpr To bit_cast(From fr) noexcept
{
    static_assert(sizeof(To) == sizeof(From));
#if defined(__GNUC__) and !defined(__clang__)
    return MIGRAPHX_CONST_FOLD(*reinterpret_cast<To*>(&fr));
#else
    return __builtin_bit_cast(To, fr);
#endif
}
} // namespace detail

template <int wm, int we, typename T, bool negative_zero_nan, bool clip>
constexpr uint8_t cast_to_f8(T _x, bool stoch, uint32_t rng)
{

    static_assert(wm + we == 7, "wm+we==7");

    const int mfmt = (sizeof(T) == 4) ? 23 : 10;
    typename detail::conditional<sizeof(T) == 2, uint16_t, uint32_t>::type x;

    if constexpr(sizeof(T) == 4)
        x = detail::bit_cast<uint32_t>(_x);
    else
        x = detail::bit_cast<uint16_t>(_x);

    uint32_t head, mantissa;
    int exponent, bias;
    uint32_t sign;

    if constexpr(sizeof(T) == 4)
    {
        head     = x & 0xFF800000;
        mantissa = x & 0x7FFFFF;
        exponent = (head >> 23) & 0xFF;
        sign     = head >> 31;
        bias     = 127;
    }
    else
    {
        head     = x & 0xFC00;
        mantissa = x & 0x3FF;
        exponent = (head >> 10) & 0x1F;
        sign     = head >> 15;
        bias     = 15;
    }

    uint32_t signed_inf = (sign << 7) + (((1 << we) - 1) << wm);
    uint32_t signed_max = (sign << 7) + ((((1 << we) - 1) << wm) + ((1 << wm) - 1));
    if(not negative_zero_nan)
    {
        signed_max = (wm == 2) ? (signed_max - 4) : (signed_max - 1);
    }

    // Deal with inf and NaNs
    if(negative_zero_nan)
    {
        if(sizeof(T) == 4)
        {
            if((x & 0x7F800000) == 0x7F800000)
                return 0x80;
        }
        else
        {
            if((x & 0x7C00) == 0x7C00)
                return 0x80;
        }
    }
    else
    {
        // calculate most common NaN mantissa for FP8, which is all Ones in binary
        uint32_t nan_mantissa = 1;
        for(auto i = 1; i < wm; ++i)
        {
            nan_mantissa |= (nan_mantissa << 1);
        }
        // TODO: abstract duplicate branches
        if(sizeof(T) == 4 and ((x & 0x7F800000) == 0x7F800000))
        {
            // infinity
            if(mantissa == 0)
            {
                if(sign == 0)
                {
                    return (wm == 2) ? 0x7B : 0x7E;
                }
                else
                {
                    return (wm == 2) ? 0xFB : 0xFE;
                }
            }
            else
            { // NaNs
                return signed_inf + nan_mantissa;
            }
        }
        else if(sizeof(T) == 2 and ((x & 0x7C00) == 0x7C00))
        {
            // infinity
            if(mantissa == 0)
            {
                if(sign == 0)
                {
                    return (wm == 2) ? 0x7B : 0x7E;
                }
                else
                {
                    return (wm == 2) ? 0xFB : 0xFE;
                }
            }
            else
            { // NaNs
                return signed_inf + nan_mantissa;
            }
        }
    }
    // handle positive zero
    if(x == 0)
        return 0;
    // handle negative zero
    if((sizeof(T) == 4 and x == 0x80000000) or (sizeof(T) == 2 and x == 0x8000))
    {
        if(negative_zero_nan)
        {
            return 0;
        }
        else
        {
            return 0x80;
        }
    }

    // First need to check if it is normal or denorm as there is a difference of implict 1
    // Then need to adjust the exponent to align with the F8 exponent, in the meanwhile, shift
    // The mantissa. Then for stochastic rounding, add rng to mantissa and truncate. And for
    // RNE, no need to add rng. Then probably need to check whether there is carry and adjust
    // exponent and mantissa again

    // For IEEE bias mode, the bias is 2^(k-1) -1 where k is the width of exponent bits
    const int f8_bias                  = (1 << (we - 1)) - 1 + (negative_zero_nan ? 1 : 0);
    const int f8_denormal_act_exponent = 1 - f8_bias; // actual exponent of f8 denormal
    // act_exponent is the actual exponent of fp32/fp16 (after subtracting bias)
    // f8_exponent is the converted f8 exponent with bias encoding
    // exponent_diff is the diff between fp32/fp16 exponent and f8 exponent,
    // the difference needs to be adjusted and mantissa shifted
    int act_exponent, f8_exponent, exponent_diff;

    if(exponent == 0)
    { // fp32/fp16 is in denormal.
        /* fp32 denormal is below 2^-127 so it is usually not a concern here, we mostly concern fp16
here. In this case, f8 is usually in denormal. But there could be exceptions. fp16 denormal has
exponent bias 15 while bf8 with NANOO has exponent bias 16. It means that there are some numbers in
fp16 denormal but they are bf8 (NANOO) normals - smallest bf8 (NANOO) normal is 2^-15. fp16 numbers
where exponent==0 (actual exponent -14) and highest bit of mantissa is 1 are bf8 (NANOO) normal. In
this case, the fp16 mantissa should be shift left by 1  */
        act_exponent  = exponent - bias + 1;
        exponent_diff = f8_denormal_act_exponent -
                        act_exponent; // actual exponent is exponent-bias+1 as it is denormal
    }
    else
    { // fp32/fp16 is normal with implicit 1
        act_exponent = exponent - bias;
        if(act_exponent <= f8_denormal_act_exponent)
        {
            /* This is the case where fp32/fp16 is normal but it is in f8 denormal range.
   For example fp8 nanoo mode, denormal exponent is -7, but if the fp32/fp16
   actual exponent is -7, it is actually larger due to the implict 1,
   Therefore it needs to be adjust to -6 and mantissa shift right by 1.
   So for fp32/fp16, exponent -8 is the cut point to convert to fp8 nanoo */
            exponent_diff = f8_denormal_act_exponent - act_exponent;
        }
        else
        {          // both fp32/fp16 and f8 are in normal range
            exponent_diff =
                0; // exponent_diff=0 does not mean there is no difference for this case,
            // act_exponent could be larger. Just that it does not need shift mantissa
        }
        mantissa += (1 << mfmt); // Add the implicit 1 into mantissa
    }

    bool midpoint = (mantissa & ((1 << (mfmt - wm + exponent_diff)) - 1)) ==
                    (1 << (mfmt - wm + exponent_diff - 1));
    /* This part is a bit tricky. The judgment of whether it is a tie needs to be done before we
 shift right as shift right could rip off some residual part and make something not midpoint look
 like midpoint. For example, the fp16 number 0x1002 (0 00100 0000000010), it is larger than
 midpoint, but after shift right by 4 bits, it would look like midpoint.
*/

    if(exponent_diff > 0)
        mantissa >>= exponent_diff;
    else if(exponent_diff == -1)
        mantissa <<= -exponent_diff;
    bool implicit_one = mantissa & (1 << mfmt);
    // if there is no implict 1, it  means the f8 is denormal and need to adjust to denorm exponent
    f8_exponent =
        (act_exponent + exponent_diff) /*actual f8 exponent*/ + f8_bias - (implicit_one ? 0 : 1);

    // Now we have the exponent and mantissa adjusted
    uint32_t drop_mask = (1 << (mfmt - wm)) - 1;
    bool odd =
        mantissa & (1 << (mfmt - wm)); // if the least significant bit that is not truncated is 1
    mantissa += (stoch ? rng : (midpoint ? (odd ? mantissa : mantissa - 1) : mantissa)) & drop_mask;

    // Now we deal with overflow
    if(f8_exponent == 0)
    {
        if((1 << mfmt) & mantissa)
        {
            f8_exponent = 1; // denormal overflow to become normal, promote exponent
        }
    }
    else
    {
        if((1 << (mfmt + 1)) & mantissa)
        {
            mantissa >>= 1;
            f8_exponent++;
        }
    }

    mantissa >>= (mfmt - wm);

    // above range: quantize to maximum possible float of the same sign
    const int max_exp = (1 << we) - (negative_zero_nan ? 1 : 2);
    // TODO: this is ugly, need better way to handle out of range values
    if(f8_exponent > max_exp)
    {
        if(clip)
        {
            return signed_max;
        }
        else
        {
            if(negative_zero_nan)
            {
                return 0x80;
            }
            else
            {
                uint32_t tmp_signed_max = (sign << 7) + ((((1 << we) - 1) << wm) + ((1 << wm) - 1));
                return (wm == 2) ? signed_inf : tmp_signed_max;
            }
        }
    }

    if(f8_exponent == 0 and mantissa == 0)
        return negative_zero_nan ? 0 : (sign << 7);
    mantissa &= (1 << wm) - 1;
    return (sign << 7) | (f8_exponent << wm) | mantissa;
}

template <int wm, int we, typename T, bool negative_zero_nan>
constexpr T cast_from_f8(uint8_t x)
{
    constexpr int weo = 8;
    constexpr int wmo = 23;

    T fInf, fNegInf, fNaN, fNeg0;
    uint32_t ifInf    = 0x7F800000;
    uint32_t ifNegInf = 0xFF800000;
    uint32_t ifNaN    = 0x7F800001;
    uint32_t ifNeg0   = 0x80000000;
    // TODO: need to change T for half but right now it would never  called with half
    fInf    = detail::bit_cast<float>(ifInf);
    fNegInf = detail::bit_cast<float>(ifNegInf);
    fNaN    = detail::bit_cast<float>(ifNaN);
    fNeg0   = detail::bit_cast<float>(ifNeg0);

    if(x == 0)
        return 0;

    uint32_t sign     = x >> 7;
    uint32_t mantissa = x & ((1 << wm) - 1);
    int exponent      = (x & 0x7F) >> wm;
    if(negative_zero_nan)
    {
        if(x == 0x80)
            return fNaN;
    }
    else
    {
        if(x == 0x80)
            return fNeg0;
        if(exponent == ((1 << we) - 1) and wm == 2)
            return (mantissa == 0) ? (sign ? fNegInf : fInf) : fNaN;
        else if(wm == 3 and (x == 0x7F or x == 0xFF))
            return fNaN;
    }
    typename detail::conditional<sizeof(T) == 2, uint16_t, uint32_t>::type retval;

    const int exp_low_cutoff = (1 << (weo - 1)) - (1 << (we - 1)) + 1 - (negative_zero_nan ? 1 : 0);

    // subnormal input
    if(exponent == 0)
    {
        // guaranteed mantissa!=0 since cases 0x0 and 0x80 are handled above
        int sh = 1 + __builtin_clz(mantissa) - (32 - wm);
        mantissa <<= sh;
        exponent += 1 - sh;
        mantissa &= ((1 << wm) - 1);
    }
    exponent += exp_low_cutoff - 1;
    mantissa <<= wmo - wm;

    // subnormal output (occurs when T=half, we=5, negative_zero_nan=true)
    if(exponent <= 0)
    {
        mantissa |= 1 << wmo;
        mantissa >>= 1 - exponent;
        exponent = 0;
    }

    if(sizeof(T) == 2)
        retval = (sign << 15) | (exponent << 10) | mantissa;
    else
        retval = (sign << 31) | (exponent << 23) | mantissa;
    return detail::bit_cast<T>(retval);
}

} // namespace migraphx_f8_impl
#endif // MIGRAPHX_FP8_IMPL_HPP
