quant_utils.cuh

#pragma once
#ifndef USE_ROCM
#include <hip/hip_fp8.h>
#endif

#include <hip/hip_fp16.h>
#include <hip/hip_bf16.h>
#include <hip/hip_bfloat16.h>

#include "../../../attention/attention_dtypes.h"

namespace vllm {
#ifdef USE_ROCM

namespace fp8 {
  // #ifdef ENABLE_FP8

// KV-CACHE int8
static inline __device__ float fp8_to_float(uint8_t input) {
  const uint32_t w = (uint32_t)input << 24;
  const uint32_t sign = w & UINT32_C(0x80000000);
  const uint32_t nonsign = w & UINT32_C(0x7FFFFFFF);
  uint32_t renorm_shift = __clz(nonsign);
  renorm_shift = renorm_shift > 4 ? renorm_shift - 4 : 0;
  uint32_t result = sign | ((nonsign << renorm_shift >> 4) + ((0x78 - renorm_shift) << 23));
  return c10::detail::fp32_from_bits(result);
}

// float -> fp8
static inline __device__ uint8_t float_to_fp8(float f) {
  constexpr uint32_t fp8_max = UINT32_C(1087) << 20;
  constexpr uint32_t denorm_mask = UINT32_C(141) << 23;
  uint32_t f_bits = c10::detail::fp32_to_bits(f);
  uint8_t result = 0u;
  const uint32_t sign = f_bits & UINT32_C(0x80000000);
  f_bits ^= sign;
  if (f_bits >= fp8_max) {
    result = 0x7f;
  } else {
    if (f_bits < (UINT32_C(121) << 23)) {
      f_bits =
        c10::detail::fp32_to_bits(c10::detail::fp32_from_bits(f_bits) + c10::detail::fp32_from_bits(denorm_mask));
      result = static_cast<uint8_t>(f_bits - denorm_mask);
    } else {
      uint8_t mant_odd = (f_bits >> 20) & 1;
      f_bits += ((uint32_t)(7 - 127) << 23) + 0x7FFFF;
      f_bits += mant_odd;
      result = static_cast<uint8_t>(f_bits >> 20);
    }
  }

  result |= static_cast<uint8_t>(sign >> 24);
  return result;
}


template <typename Tout, typename Tin>
__inline__ __device__ Tout scaled_vec_conversion(const Tin& x,
                                                 const float scale) {
  return x;
}

using __nv_bfloat16 = __hip_bfloat16;

// fp8 -> __nv_bfloat16
template <>
__inline__ __device__ __nv_bfloat16
scaled_vec_conversion<__nv_bfloat16, uint8_t>(const uint8_t& a, float scale) {

  return __float2bfloat16(fp8_to_float(a) * scale);
}

// fp8x2 -> __nv_bfloat162
template <>
__inline__ __device__ __nv_bfloat162
scaled_vec_conversion<__nv_bfloat162, uint16_t>(const uint16_t& a,
                                                float scale) {
  __nv_bfloat162 res;
  res.x = scaled_vec_conversion<__nv_bfloat16, uint8_t>((uint8_t)a, scale);
  res.y =
      scaled_vec_conversion<__nv_bfloat16, uint8_t>((uint8_t)(a >> 8U), scale);
  return res;
}

// fp8x4 -> bf16_4_t
template <>
__inline__ __device__ bf16_4_t
scaled_vec_conversion<bf16_4_t, uint32_t>(const uint32_t& a, float scale) {
  bf16_4_t res;
  res.x = scaled_vec_conversion<__nv_bfloat162, uint16_t>((uint16_t)a, scale);
  res.y = scaled_vec_conversion<__nv_bfloat162, uint16_t>((uint16_t)(a >> 16U),
                                                          scale);
  return res;
}

// fp8x8 -> bf16_8_t
template <>
__inline__ __device__ bf16_8_t
scaled_vec_conversion<bf16_8_t, uint2>(const uint2& a, float scale) {
  bf16_4_t tmp1, tmp2;
  tmp1 = scaled_vec_conversion<bf16_4_t, uint32_t>(a.x, scale);
  tmp2 = scaled_vec_conversion<bf16_4_t, uint32_t>(a.y, scale);
  bf16_8_t res;
  res.x = tmp1.x;
  res.y = tmp1.y;
  res.z = tmp2.x;
  res.w = tmp2.y;
  return res;
}

// fp8 -> float
template <>
__inline__ __device__ float scaled_vec_conversion<float, uint8_t>(
    const uint8_t& a, float scale) {
    return fp8_to_float(a) * scale;
}

// fp8x2 -> float2
template <>
__inline__ __device__ float2
scaled_vec_conversion<float2, uint16_t>(const uint16_t& a, float scale) {
    float2 f2r;
    f2r.x = scaled_vec_conversion<float, uint8_t>((uint8_t)a, scale);
    f2r.y = scaled_vec_conversion<float, uint8_t>((uint8_t)(a >> 8U), scale);
    return f2r;
}

// fp8x4 -> float4
template <>
__inline__ __device__ Float4_
scaled_vec_conversion<Float4_, uint32_t>(const uint32_t& a, const float scale) {
  Float4_ res;
  res.x = scaled_vec_conversion<float2, uint16_t>((uint16_t)a, scale);
  res.y = scaled_vec_conversion<float2, uint16_t>((uint16_t)(a >> 16U), scale);
  return res;
}

// fp8x4 -> float4
template <>
__inline__ __device__ float4
scaled_vec_conversion<float4, uint32_t>(const uint32_t& a, float scale) {
  Float4_ res = scaled_vec_conversion<Float4_, uint32_t>(a, scale);
  return {res.x.x, res.x.y, res.y.x, res.y.y};
}

// fp8x8 -> float8
template <>
__inline__ __device__ Float8_
scaled_vec_conversion<Float8_, uint2>(const uint2& a, float scale) {
  Float4_ tmp1, tmp2;
  tmp1 = scaled_vec_conversion<Float4_, uint32_t>(a.x, scale);
  tmp2 = scaled_vec_conversion<Float4_, uint32_t>(a.y, scale);
  Float8_ res;
  res.x = tmp1.x;
  res.y = tmp1.y;
  res.z = tmp2.x;
  res.w = tmp2.y;
  return res;
}

// fp8 -> half
template <>
__inline__ __device__ uint16_t
scaled_vec_conversion<uint16_t, uint8_t>(const uint8_t& a, float scale) {
  float res = fp8_to_float(a) * scale;
  return float_to_half(res);
}

// fp8x2 -> half2
template <>
__inline__ __device__ uint32_t
scaled_vec_conversion<uint32_t, uint16_t>(const uint16_t& a, float scale) {
  union {
    uint16_t u16[2];
    uint32_t u32;
  } res;
  res.u16[0] = scaled_vec_conversion<uint16_t, uint8_t>((uint8_t)a, scale);
  res.u16[1] = scaled_vec_conversion<uint16_t, uint8_t>((uint8_t)(a >> 8U), scale);
  return res.u32;
}

// fp8x4 -> half2x2
template <>
__inline__ __device__ uint2
scaled_vec_conversion<uint2, uint32_t>(const uint32_t& a, float scale) {
  union {
    uint2 u32x2;
    uint32_t u32[2];
  } tmp;
  tmp.u32[0] = scaled_vec_conversion<uint32_t, uint16_t>((uint16_t)a, scale);
  tmp.u32[1] = scaled_vec_conversion<uint32_t, uint16_t>((uint16_t)(a >> 16U), scale);
  return tmp.u32x2;
}

// fp8x8 -> half2x4
template <>
__inline__ __device__ uint4 scaled_vec_conversion<uint4, uint2>(const uint2& a,
                                                                float scale) {
  union {
    uint4 u64x2;
    uint2 u64[2];
  } tmp;
  tmp.u64[0] = scaled_vec_conversion<uint2, uint32_t>(a.x, scale);
  tmp.u64[1] = scaled_vec_conversion<uint2, uint32_t>(a.y, scale);
  return tmp.u64x2;
}

// half -> fp8
template <>
__inline__ __device__ uint8_t
scaled_vec_conversion<uint8_t, uint16_t>(const uint16_t& a, float scale) {
  float res_f = half_to_float(a) / scale;
  return float_to_fp8(res_f);
}

// halfx2 -> fp8x2
template <>
__inline__ __device__ uint16_t
scaled_vec_conversion<uint16_t, uint32_t>(const uint32_t& a, float scale) {
  union {
    uint8_t ui8[2];
    uint16_t ui16;
  } tmp;
  union {
    uint32_t ui32;
    half2 h2r;
  } tmp_a;
  tmp_a.ui32 = a;
  tmp.ui8[0] = scaled_vec_conversion<uint8_t, uint16_t>(tmp_a.h2r.data[0], scale);
  tmp.ui8[1] = scaled_vec_conversion<uint8_t, uint16_t>(tmp_a.h2r.data[1], scale);
  return tmp.ui16;
}

// half2x2 -> fp8x4
template <>
__inline__ __device__ uint32_t
scaled_vec_conversion<uint32_t, uint2>(const uint2& a, float scale) {
  union {
    uint16_t ui16[2];
    uint32_t ui32;
  } tmp;
  tmp.ui16[0] = scaled_vec_conversion<uint16_t, uint32_t>(a.x, scale);
  tmp.ui16[1] = scaled_vec_conversion<uint16_t, uint32_t>(a.y, scale);
  return tmp.ui32;
}

// half2x4 -> fp8x8
template <>
__inline__ __device__ uint2 scaled_vec_conversion<uint2, uint4>(const uint4& a,
                                                                float scale) {
  union {
    uint2 ui2[2];
    uint4 ui4;
  } tmp;
  tmp.ui4 = a;
  uint2 res;
  res.x = scaled_vec_conversion<uint32_t, uint2>(tmp.ui2[0], scale);
  res.y = scaled_vec_conversion<uint32_t, uint2>(tmp.ui2[1], scale);
  return res;
}

// bf16 -> fp8
template <>
__inline__ __device__ uint8_t scaled_vec_conversion<uint8_t, __nv_bfloat16>(
    const __nv_bfloat16& a, float scale) {
      float res_f = (static_cast<float>(a)) / scale;
      return float_to_fp8(res_f);
}

// bf16x2 -> fp8x2
template <>
__inline__ __device__ uint16_t scaled_vec_conversion<uint16_t, __nv_bfloat162>(
    const __nv_bfloat162& a, float scale) {
  union {
    uint8_t ui8[2];
    uint16_t ui16;
  } tmp;
  tmp.ui8[0] = scaled_vec_conversion<uint8_t, __nv_bfloat16>(a.x, scale);
  tmp.ui8[1] = scaled_vec_conversion<uint8_t, __nv_bfloat16>(a.y, scale);
  return tmp.ui16;
}

// bf16x4 -> fp8x4
template <>
__inline__ __device__ uint32_t
scaled_vec_conversion<uint32_t, bf16_4_t>(const bf16_4_t& a, float scale) {
  union {
    uint16_t ui16[2];
    uint32_t ui32;
  } tmp;
  tmp.ui16[0] = scaled_vec_conversion<uint16_t, __nv_bfloat162>(a.x, scale);
  tmp.ui16[1] = scaled_vec_conversion<uint16_t, __nv_bfloat162>(a.y, scale);
  return tmp.ui32;
}

// bf16x8 -> fp8x8
template <>
__inline__ __device__ uint2
scaled_vec_conversion<uint2, bf16_8_t>(const bf16_8_t& a, float scale) {
  uint2 res;
  res.x = scaled_vec_conversion<uint32_t, bf16_4_t>({a.x, a.y}, scale);
  res.y = scaled_vec_conversion<uint32_t, bf16_4_t>({a.z, a.w}, scale);
  return res;
}

// float -> fp8
template <>
__inline__ __device__ uint8_t
scaled_vec_conversion<uint8_t, float>(const float& a, float scale) {
  return float_to_fp8(a / scale);
}

// floatx2 -> fp8x2
template <>
__inline__ __device__ uint16_t
scaled_vec_conversion<uint16_t, float2>(const float2& a, float scale) {
  union {
    uint8_t ui8[2];
    uint16_t ui16;
  } tmp;
  tmp.ui8[0] = scaled_vec_conversion<uint8_t, float>(a.x, scale);
  tmp.ui8[1] = scaled_vec_conversion<uint8_t, float>(a.y, scale);
  return tmp.ui16;
}

// floatx4 -> fp8x4
template <>
__inline__ __device__ uint32_t
scaled_vec_conversion<uint32_t, float4>(const float4& a, float scale) {
  union {
    uint16_t ui16[2];
    uint32_t ui32;
  } tmp;
  tmp.ui16[0] = scaled_vec_conversion<uint16_t, float2>({a.x, a.y}, scale);
  tmp.ui16[1] = scaled_vec_conversion<uint16_t, float2>({a.z, a.w}, scale);
  return tmp.ui32;
}

inline __device__ uint8_t float_to_fp8e5m2(float f) {
  constexpr uint32_t fp32_inf = UINT32_C(255) << 23;
  constexpr uint32_t fp8_max = UINT32_C(143) << 23;
  constexpr uint32_t denorm_mask = UINT32_C(134) << 23;
  uint32_t f_bits = c10::detail::fp32_to_bits(f);
  uint8_t result = 0u;
  const uint32_t sign = f_bits & UINT32_C(0x80000000);
  f_bits ^= sign;
  if (f_bits >= fp8_max) {
    result = f_bits > fp32_inf ? UINT8_C(0x7F) : UINT8_C(0x7C);
  } else {
    if (f_bits < (UINT32_C(113) << 23)) {
      f_bits = c10::detail::fp32_to_bits(c10::detail::fp32_from_bits(f_bits)
               + c10::detail::fp32_from_bits(denorm_mask));
      result = static_cast<uint8_t>(f_bits - denorm_mask);
    } else {
      uint32_t mant_odd = (f_bits >> 21) & 1;
      f_bits += ((uint32_t)(15 - 127) << 23) + 0xFFFFF;
      f_bits += mant_odd;
      result = static_cast<uint8_t>(f_bits >> 21);
    }
  }
  result |= static_cast<uint8_t>(sign >> 24);
  return result;
}

//  fp8
template <typename Tin>
__inline__ __device__ uint8_t
scaled_vec_conversion_to_e5m2(const Tin& a, float scale) {
  return 0;
}

// float -> fp8
template <>
__inline__ __device__ uint8_t
scaled_vec_conversion_to_e5m2<float>(const float& a, float scale) {
  return float_to_fp8e5m2(a / scale);
}

// half -> fp8
template <>
__inline__ __device__ uint8_t
scaled_vec_conversion_to_e5m2<uint16_t>(const uint16_t& a, float scale) {
  float res_f = half_to_float(a) / scale;
  return float_to_fp8e5m2(res_f);
}

// bf16 -> fp8
template <>
__inline__ __device__ uint8_t 
scaled_vec_conversion_to_e5m2<__nv_bfloat16>(const __nv_bfloat16& a, float scale) {
  float res_f = (static_cast<float>(a)) / scale;
  return float_to_fp8e5m2(res_f);
}

inline __device__ float fp8e5m2_to_fp32(const uint8_t& input) {
  union uf16{
    uint16_t as_bits;
    _Float16 as_value;
  } ;
  uf16 u16;
  u16.as_bits = (uint16_t)input << 8;
  return (float)u16.as_value;
}

template <typename Tout>
__inline__ __device__ Tout
scaled_vec_conversion_from_e5m2(const uint8_t& a, float scale) {
  return 0;
}

// fp8 ->  float
template <>
__inline__ __device__ float
scaled_vec_conversion_from_e5m2<float>(const uint8_t& a, float scale) {
  return fp8e5m2_to_fp32(a)*scale;
}

// fp8  -> half
template <>
__inline__ __device__ uint16_t
scaled_vec_conversion_from_e5m2<uint16_t>(const uint8_t& a, float scale) {
  return float_to_half(fp8e5m2_to_fp32(a)*scale);
}

// fp8  -> bf16
template <>
__inline__ __device__ __nv_bfloat16 
scaled_vec_conversion_from_e5m2<__nv_bfloat16>(const uint8_t& a, float scale) {
  return __float2bfloat16(fp8e5m2_to_fp32(a)*scale);
}



template <typename Tout, typename Tin, Fp8KVCacheDataType kv_dt>
__inline__ __device__ Tout scaled_convert(const Tin& x, const float scale) {
  if constexpr (kv_dt == Fp8KVCacheDataType::kFp8E4M3) {
    return scaled_vec_conversion<Tout, Tin>(x, scale);
  }
  else if constexpr(kv_dt == Fp8KVCacheDataType::kFp8E5M2 && sizeof(Tout)==1){
    return scaled_vec_conversion_to_e5m2<Tin>(x, scale);
  }
  else if constexpr(kv_dt == Fp8KVCacheDataType::kFp8E5M2 && sizeof(Tin)==1){
    return scaled_vec_conversion_from_e5m2<Tout>(x, scale);
  }
  return {};  // Squash missing return statement warning
}

  // The following macro is used to dispatch the conversion function based on
  // the data type of the key and value cache. The FN is a macro that calls a
  // function with template<typename scalar_t, typename cache_t,
  // Fp8KVCacheDataType kv_dt>.
 #define DISPATCH_BY_KV_CACHE_DTYPE(SRC_DTYPE, KV_DTYPE, FN)                  \
    if (KV_DTYPE == "auto") {                                                  \
      if (SRC_DTYPE == at::ScalarType::Float) {                                \
        FN(float, float, vllm::Fp8KVCacheDataType::kAuto);                     \
      } else if (SRC_DTYPE == at::ScalarType::Half) {                          \
        FN(uint16_t, uint16_t, vllm::Fp8KVCacheDataType::kAuto);               \
      } else if (SRC_DTYPE == at::ScalarType::BFloat16) {                      \
        FN(__nv_bfloat16, __nv_bfloat16, vllm::Fp8KVCacheDataType::kAuto);     \
      } else {                                                                 \
        TORCH_CHECK(false, "Unsupported input type of kv cache: ", SRC_DTYPE); \
      }                                                                        \
    } else {                                                                   \
      if (KV_DTYPE == "fp8" || KV_DTYPE == "fp8_e4m3") {                       \
        if (SRC_DTYPE == at::ScalarType::Float) {                              \
          FN(float, uint8_t, vllm::Fp8KVCacheDataType::kFp8E4M3);              \
        } else if (SRC_DTYPE == at::ScalarType::Half) {                        \
          FN(uint16_t, uint8_t, vllm::Fp8KVCacheDataType::kFp8E4M3);           \
        } else if (SRC_DTYPE == at::ScalarType::BFloat16) {                    \
          FN(__nv_bfloat16, uint8_t, vllm::Fp8KVCacheDataType::kFp8E4M3);      \
        } else {                                                               \
          TORCH_CHECK(false,                                                   \
                      "Unsupported input type of kv cache: ", SRC_DTYPE);      \
        }                                                                      \
      } else if (KV_DTYPE == "fp8_e5m2") {                                     \
        if (SRC_DTYPE == at::ScalarType::Float) {                              \
          FN(float, uint8_t, vllm::Fp8KVCacheDataType::kFp8E5M2);              \
        } else if (SRC_DTYPE == at::ScalarType::Half) {                        \
          FN(uint16_t, uint8_t, vllm::Fp8KVCacheDataType::kFp8E5M2);           \
        } else if (SRC_DTYPE == at::ScalarType::BFloat16) {                    \
          FN(__nv_bfloat16, uint8_t, vllm::Fp8KVCacheDataType::kFp8E5M2);      \
        } else {                                                               \
          TORCH_CHECK(false,                                                   \
                      "Unsupported input type of kv cache: ", SRC_DTYPE);      \
        }                                                                      \
      } else {                                                                 \
        TORCH_CHECK(false, "Unsupported data type of kv cache: ", KV_DTYPE);   \
      }                                                                        \
    }


}  // namespace fp8
#endif  // USE_ROCM
}  // namespace vllm