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#ifndef MIGRAPHX_GUARD_KERNELS_FP8_IMPL_HPP
#define MIGRAPHX_GUARD_KERNELS_FP8_IMPL_HPP
#include <migraphx/kernels/bit_cast.hpp>
#include <migraphx/kernels/type_traits.hpp>
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wreserved-identifier"
#endif

namespace migraphx {

namespace fp8 {
namespace impl {

// NOLINTBEGIN
template <int Wm, int We, typename T, bool NegativeZeroNan, bool Clip>
__device__ constexpr uint8_t cast_to_f8(T f_x, bool stoch = false, uint32_t rng = 0)
{
    constexpr bool is_float = true;
    // half is not supported for now
    constexpr bool is_half = false;
    static_assert(Wm + We == 7, "Wm+We==7");
    static_assert(is_float or is_half, "Only float can be cast to f8");

    const uint32_t mfmt = (sizeof(T) == 4) ? 23 : 10;
    typename migraphx::conditional_t<sizeof(T) == 2, uint16_t, uint32_t> x;

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

    uint32_t head     = 0;
    uint32_t mantissa = 0;
    int exponent      = 0;
    uint32_t bias     = 0;
    uint32_t sign     = 0;
    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_all_ones = (sign << 7) + ((((1 << We) - 1) << Wm) + ((1 << Wm) - 1));

    // Calcualte maximum singed value FLT_MAX, FLT_MIN
    uint32_t signed_max = signed_all_ones;
    if(not NegativeZeroNan)
        signed_max = (Wm == 2) ? (signed_max - 4) : (signed_max - 1);

    // Deal with inf and NaNs
    if(NegativeZeroNan) // For the FNUZ cases, it is simple just return NaNs
    {
        if((sizeof(T) == 4 and ((x & 0x7F800000) == 0x7F800000)) or
           (sizeof(T) == 2 and ((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);
        }
        if((sizeof(T) == 4 and ((x & 0x7F800000) == 0x7F800000)) or
           (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
    else if((sizeof(T) == 4 and x == 0x80000000) or (sizeof(T) == 2 and x == 0x8000))
    {
        return NegativeZeroNan ? 0 : 0x80; // For FNUZ types neg zero is just positive zero
    }

    /* 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 - 1u)) - 1 + (NegativeZeroNan ? 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  = 0;
    int f8_exponent   = 0;
    int exponent_diff = 0;

    if(exponent == 0 and mantissa != 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 FNUZ has exponent bias 16. It means that there are some
        numbers in fp16 denormal but they are bf8 (FNUZ) normals - smallest bf8 (FNUZ) normal is
        2^-15. fp16 numbers where exponent==0 (actual exponent -14) and highest bit of mantissa is 1
        are bf8 (FNUZ) normal. In this case, the fp16 mantissa should be shift left by 1  */
        act_exponent  = 1 - bias;
        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 FNUZ 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 FNUZ */
            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
    }

    // need to know whether the number is right in the middle of two adjacent fp8 numbers. use  max
    // value of 31 to avoid undefined behaviour
    bool midpoint = (mantissa & ((1u << (mfmt - Wm + exponent_diff)) - 1)) ==
                    (1u << (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
    /*
    This part is doing rounding by adding mantissa part that is going to get dropped.
    e.g. if the dropped part for less than 0.5 than it would round down.
    if the dropped part is more than 0.5 then it would round up by rolling carry to LSB of retained
    mantissa.
    For the mid point when bit pattern is like this for Odd: `xy1:10000000` for Odd and
    `xy0:10000000` for the Even.  where `:` is delimiter for dropped v/s retained part.
    For the odd case :
    this will add xy1:10000000 + 000:10000000 which would roll over carry to LSB of retained
    part making it RNE.
    For the even case : this will add xy0:10000000 + 000:01111111 which would
    round down and keep number Even
    */
    mantissa += (stoch ? rng : (midpoint ? (odd ? mantissa : mantissa - 1) : mantissa)) & drop_mask;

    // Now we deal with overflow
    if(f8_exponent == 0 and ((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
    // for e5m2 case, max_exp is 14, since exp = 15 is reserved for Infs and Nans
    const int max_exp = (1 << We) - ((NegativeZeroNan or Wm == 3) ? 1 : 2);
    if(f8_exponent > max_exp)
    {
        if(Clip)
            return signed_max;
        else
        {
            // https://onnx.ai/onnx/technical/float8.html#cast
            if(NegativeZeroNan)
                return 0x80;
            else
                return (Wm == 2) ? signed_inf : signed_all_ones;
        }
    }

    if(f8_exponent == 0 and mantissa == 0)
        return NegativeZeroNan ? 0 : (sign << 7);
    mantissa &= (1 << Wm) - 1;
    return (sign << 7) | (f8_exponent << Wm) | mantissa;
}
// NOLINTEND

template <int Wm, int We, typename T, bool NegativeZeroNan>
__device__ constexpr T cast_from_f8(uint8_t x)
{
    // half is not supported for now
    constexpr bool is_half  = false;
    constexpr bool is_float = true;
    static_assert(is_float or is_half, "Only float are supported");

    constexpr int weo = is_half ? 5 : 8;
    constexpr int wmo = is_half ? 10 : (is_float ? 23 : 7);
    // NOLINTNEXTLINE
    T f_inf, f_neg_inf, f_nan, f_neg0;

    if constexpr(is_float)
    {
        const uint32_t if_inf     = 0x7F800000;
        const uint32_t if_neg_inf = 0xFF800000;
        const uint32_t if_nan     = 0x7F800001;
        const uint32_t if_neg0    = 0x80000000;
        f_inf                     = migraphx::bit_cast<float>(if_inf);
        f_neg_inf                 = migraphx::bit_cast<float>(if_neg_inf);
        f_nan                     = migraphx::bit_cast<float>(if_nan);
        f_neg0                    = migraphx::bit_cast<float>(if_neg0);
    }

    if(x == 0)
        return 0;

    uint32_t sign     = x >> 7;              // NOLINT
    uint32_t mantissa = x & ((1 << Wm) - 1); // NOLINT
    int exponent      = (x & 0x7F) >> Wm;    // NOLINT
    if(NegativeZeroNan)
    {
        if(x == 0x80)
            return f_nan;
    }
    else
    {
        if(x == 0x80)
            return f_neg0;
        if(exponent == ((1 << We) - 1) and Wm == 2) // NOLINT
            return (mantissa == 0) ? (sign ? f_neg_inf : f_inf) : f_nan;
        else if(Wm == 3 and (x == 0x7F or x == 0xFF))
            return f_nan;
    }
    typename migraphx::conditional_t<sizeof(T) == 2, uint16_t, uint32_t> retval;

    const int exp_low_cutoff =
        (1 << (weo - 1)) - (1 << (We - 1)) + 1 - (NegativeZeroNan ? 1 : 0); // NOLINT

    // 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;             // NOLINT
        exponent += 1 - sh;
        mantissa &= ((1 << Wm) - 1); // NOLINT
    }
    exponent += exp_low_cutoff - 1;
    mantissa <<= wmo - Wm; // NOLINT

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

    if(sizeof(T) == 2)
        retval = (sign << 15) | (exponent << 10) | mantissa; // NOLINT
    else
        retval = (sign << 31) | (exponent << 23) | mantissa; // NOLINT
    return migraphx::bit_cast<T>(retval);
}
} // namespace impl
} // namespace fp8
} // namespace migraphx
#if defined(__clang__)
#pragma clang diagnostic pop
#endif
#endif // MIGRAPHX_GUARD_KERNELS_FP8_IMPL_HPP
