TheRock/rocm-libraries/projects/composablekernel/include/ck/utility/e4m3.hpp

// Copyright (c) Advanced Micro Devices, Inc., or its affiliates.
// SPDX-License-Identifier: MIT

#pragma once

#ifndef CK_CODE_GEN_RTC

#include "ck/utility/scale_utils.hpp"
#include "ck/utility/type.hpp"

namespace ck {

struct e4m3_scale_t
{
    using type   = uint8_t;
    using Format = utils::ScaleFormat<4, 3>;

    static constexpr int exponent_bits = Format::exponent_bits;
    static constexpr int mantissa_bits = Format::mantissa_bits;
    static constexpr type value_mask   = Format::value_mask;
    static constexpr type nan_mask     = Format::nan_mask;
    static constexpr type max_finite   = Format::max_finite;
    static constexpr int bias          = Format::bias;

    type data;

    __host__ __device__ constexpr e4m3_scale_t() : data{type{}} {}
    __host__ __device__ constexpr explicit e4m3_scale_t(type init)
        : data{static_cast<type>(init & value_mask)}
    {
    }
    __host__ __device__ constexpr explicit e4m3_scale_t(int init)
        : data{static_cast<type>(static_cast<type>(init) & value_mask)}
    {
    }
    __host__ __device__ explicit e4m3_scale_t(float scale)
    {
#if defined(__gfx1250__)
        union
        {
            float fval;
            uint32_t i32val;
            uint8_t i8val[4];
        } val;
        val.fval             = scale;
        uint32_t ival        = 0;
        const float max_e4m3 = 448.0f;
        // if x is not +/- infinity or nan
        if((val.i32val & 0x7F800000) != 0x7F800000)
            // clip float value
            val.fval = __builtin_amdgcn_fmed3f(val.fval, max_e4m3, -max_e4m3);
        ival       = __builtin_amdgcn_cvt_pk_fp8_f32(val.fval, val.fval, ival, false);
        val.i32val = ival;
        data       = val.i8val[0] & value_mask; // apply a 7-bit mask
#else
        data = Format::encode(scale);
#endif
    }

    __host__ __device__ explicit operator float() const
    {
#if defined(__gfx1250__)
        union
        {
            unsigned int i32val;
            uint8_t i8val[4];
        } val;
        val.i8val[0] = this->data;
        return __builtin_amdgcn_cvt_f32_fp8(val.i32val, false);
#else
        return Format::decode(data);
#endif
    }

    __host__ __device__ constexpr bool operator==(const e4m3_scale_t& other) const
    {
        return data == other.data && !is_nan();
    }

    __host__ __device__ constexpr bool operator!=(const e4m3_scale_t& other) const
    {
        return !(*this == other);
    }

    __host__ __device__ constexpr bool is_nan() const { return Format::is_nan(data); }
};

namespace utils {

template <>
__host__ __device__ inline constexpr int32_t get_exponent_value<e4m3_scale_t>(e4m3_scale_t x)
{
    return e4m3_scale_t::Format::exponent(x.data);
}

} // namespace utils

} // namespace ck

#endif