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/*!
    \file
    \brief Defines a class for using integer types smaller than one byte in host
   or device code.
*/
#pragma once

#if defined(__CUDACC_RTC__)
#include <cuda/std/cstdint>
#else
#include <cstdint>
#endif

#include "cutlass/platform/platform.h"

namespace cutlass {

///////////////////////////////////////////////////////////////////////////////////////////////////

/// 4-bit signed integer type
template <int Bits, bool Signed = true>
struct integer_subbyte {
    /// Number of bits
    static int const kBits = Bits;

    /// Whether type is signed
    static bool const kSigned = Signed;

    /// External type
    using T = typename platform::conditional<kSigned, int, unsigned>::type;

    /// Storage type
    using Storage = uint8_t;

    /// Bitmask used to truncate from larger integers
    static Storage const kMask = Storage((1 << kBits) - 1);

    //
    // Data members
    //

    Storage storage;

    //
    // Methods
    //

    /// No operation
    CUTLASS_HOST_DEVICE
    integer_subbyte() {}

    /// Conversion from integer type
    CUTLASS_HOST_DEVICE
    integer_subbyte(int value)
            : storage(reinterpret_cast<Storage const&>(value) & kMask) {}

    CUTLASS_HOST_DEVICE
    integer_subbyte(unsigned value)
            : storage(reinterpret_cast<Storage const&>(value) & kMask) {}

    CUTLASS_HOST_DEVICE
    integer_subbyte(double value) {
        T tmp = static_cast<T>(value);
        storage = Storage(reinterpret_cast<unsigned const&>(tmp) & kMask);
    }

    ///
    CUTLASS_HOST_DEVICE
    operator T() const {
        if (kSigned) {
            // Sign extend
            if (storage & Storage(1 << (kBits - 1))) {
                return T(storage) | ~T(kMask);
            }
        }
        return T(storage);
    }

    /// Equality
    CUTLASS_HOST_DEVICE
    bool operator==(integer_subbyte const& rhs) const {
        return storage == rhs.storage;
    }

    /// Inequality
    CUTLASS_HOST_DEVICE
    bool operator!=(integer_subbyte const& rhs) const {
        return storage != rhs.storage;
    }

    /// Less than or equal
    CUTLASS_HOST_DEVICE
    bool operator<=(integer_subbyte const& rhs) const {
        if (kSigned) {
            if (storage & (1 << (kBits - 1))) {
                return !(rhs.storage < storage);
            }
        }
        return storage <= rhs.storage;
    }

    /// Less than
    CUTLASS_HOST_DEVICE
    bool operator<(integer_subbyte const& rhs) const {
        if (kSigned) {
            if (storage & (1 << (kBits - 1))) {
                return !(rhs.storage <= storage);
            }
        }
        return storage < rhs.storage;
    }

    /// Greater than or equal
    CUTLASS_HOST_DEVICE
    bool operator>=(integer_subbyte const& rhs) const { return !(*this < rhs); }

    /// Greater than
    CUTLASS_HOST_DEVICE
    bool operator>(integer_subbyte const& rhs) const { return !(rhs < *this); }
};

///////////////////////////////////////////////////////////////////////////////////////////////////

/// 1-bit Unsigned integer type
using uint1b_t = integer_subbyte<1, false>;

/// 2-bit Integer type
using int2b_t = integer_subbyte<2, true>;

/// 2-bit Unsigned integer type
using uint2b_t = integer_subbyte<2, false>;

/// 4-bit Integer type
using int4b_t = integer_subbyte<4, true>;

/// 4-bit Unsigned integer type
using uint4b_t = integer_subbyte<4, false>;

///////////////////////////////////////////////////////////////////////////////////////////////////

/// Defines the size of an element in bits - specialized for uint1b_t
template <>
struct sizeof_bits<uint1b_t> {
    static int const value = 1;
};

/// Defines the size of an element in bits - specialized for int2b_t
template <>
struct sizeof_bits<int2b_t> {
    static int const value = 2;
};

/// Defines the size of an element in bits - specialized for uint2b_t
template <>
struct sizeof_bits<uint2b_t> {
    static int const value = 2;
};

/// Defines the size of an element in bits - specialized for int4b_t
template <>
struct sizeof_bits<int4b_t> {
    static int const value = 4;
};

/// Defines the size of an element in bits - specialized for uint4b_t
template <>
struct sizeof_bits<uint4b_t> {
    static int const value = 4;
};

///////////////////////////////////////////////////////////////////////////////////////////////////

namespace platform {

template <>
struct numeric_limits<cutlass::int4b_t> {
    CUTLASS_HOST_DEVICE
    static cutlass::int4b_t const lowest() noexcept { return -8; }
    CUTLASS_HOST_DEVICE
    static cutlass::int4b_t const max() noexcept { return 7; }
};

template <>
struct numeric_limits<cutlass::uint4b_t> {
    CUTLASS_HOST_DEVICE
    static cutlass::uint4b_t const lowest() noexcept { return 0; }
    CUTLASS_HOST_DEVICE
    static cutlass::uint4b_t const max() noexcept { return 15; }
};

///////////////////////////////////////////////////////////////////////////////////////////////////

}  // namespace platform
}  // namespace cutlass
