sglang/sgl-kernel/csrc/cpu/vec.h

#pragma once

#if defined(__AVX512F__) && defined(__AVX512BF16__) && defined(__AMX_BF16__)
#define CPU_CAPABILITY_AVX512
#endif

#include <ATen/cpu/vec/functional.h>
#include <ATen/cpu/vec/vec.h>

namespace {

using namespace at::vec;

template <typename scalar_t, typename std::enable_if_t<is_reduced_floating_point_v<scalar_t>, int> = 0>
inline Vectorized<scalar_t> convert_from_float_ext(const Vectorized<float>& a, const Vectorized<float>& b) {
  return at::vec::convert_from_float<scalar_t>(a, b);
}

#if defined(CPU_CAPABILITY_AVX512)

// `at::vec::convert_from_float<>` from PyTorch doesn't have avx512-bf16 intrinsics
// use native instruction for bfloat16->float32 conversion
template <>
inline Vectorized<at::BFloat16>
convert_from_float_ext<at::BFloat16>(const Vectorized<float>& a, const Vectorized<float>& b) {
  return (__m512i)(_mm512_cvtne2ps_pbh(__m512(b), __m512(a)));
}

#define CVT_BF16_TO_FP32(a) _mm512_castsi512_ps(_mm512_slli_epi32(_mm512_cvtepu16_epi32(a), 16))

#define CVT_FP16_TO_FP32(a) _mm512_cvtps_ph(a, (_MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC))

inline __m512bh cvt_e4m3_bf16_intrinsic_without_denorm(__m256i fp8_vec) {
  // The following conversion is without denorm behavior, that is to say,
  //   Max subnorm   : S.0000.111 = 0.875 ∗ 2**(−6)
  //   Min subnorm   : S.0000.001 = 2**(−9)
  // 0.0019 ~ 0.0137 cannot be converted correctly.
  __m512i x = _mm512_cvtepu8_epi16(fp8_vec);
  auto mask = _mm512_cmpneq_epi16_mask(
      _mm512_and_si512(x, _mm512_set1_epi16(127)),
      _mm512_setzero_si512());  // mask = x & 0x7f
  auto mask_nan = _mm512_cmpneq_epi16_mask(
      _mm512_and_si512(x, _mm512_set1_epi16(127)),
      _mm512_set1_epi16(127));                                                      // mask_nan = x & 0x7f
  auto mantissa = _mm512_slli_epi16(_mm512_and_si512(x, _mm512_set1_epi16(7)), 4);  // mantissa = (x & 7) << 4
  auto exponent = _mm512_add_epi16(
      _mm512_srli_epi16(_mm512_and_si512(x, _mm512_set1_epi16(120)), 3),
      _mm512_set1_epi16(120));  // exponent = (((x >> 3) & 15) + 120)
  auto nonsign = _mm512_maskz_mov_epi16(mask, _mm512_or_si512(mantissa, _mm512_slli_epi16(exponent, 7)));
  nonsign = _mm512_mask_mov_epi16(_mm512_set1_epi16(0x7fff), mask_nan, nonsign);  // deal with Nan
  return (__m512bh)(_mm512_or_si512(
      nonsign,
      _mm512_slli_epi16(
          _mm512_and_si512(x, _mm512_set1_epi16(128)),
          8)));  // add sign (x & 128) << 8
}

inline __m512bh cvt_e4m3_bf16_intrinsic_with_denorm(__m256i fp8_vec) {
  __m512i x = _mm512_cvtepu8_epi16(fp8_vec);
  __m512i lg2mant = _mm512_mask_mov_epi16(
      _mm512_mask_mov_epi16(
          _mm512_setzero_si512(), _mm512_test_epi16_mask(x, _mm512_set1_epi16(2)), _mm512_set1_epi16(1)),
      _mm512_test_epi16_mask(x, _mm512_set1_epi16(4)),
      _mm512_set1_epi16(2));
  return (__m512bh)(_mm512_or_si512(
      _mm512_maskz_mov_epi16(
          _mm512_cmpneq_epi16_mask(_mm512_and_si512(x, _mm512_set1_epi16(127)), _mm512_setzero_si512()),
          _mm512_mask_blend_epi16(
              _mm512_test_epi16_mask(x, _mm512_set1_epi16(120)),
              _mm512_or_si512(
                  _mm512_and_si512(
                      _mm512_sllv_epi16(
                          _mm512_and_si512(x, _mm512_set1_epi16(3)), _mm512_sub_epi16(_mm512_set1_epi16(7), lg2mant)),
                      _mm512_set1_epi16(0x007f)),
                  _mm512_slli_epi16(_mm512_add_epi16(lg2mant, _mm512_set1_epi16(118)), 7)),
              _mm512_or_si512(
                  _mm512_slli_epi16(_mm512_and_si512(x, _mm512_set1_epi16(7)), 4),
                  _mm512_slli_epi16(
                      _mm512_add_epi16(
                          _mm512_srli_epi16(_mm512_and_si512(x, _mm512_set1_epi16(120)), 3), _mm512_set1_epi16(120)),
                      7)))),
      _mm512_slli_epi16(_mm512_and_si512(x, _mm512_set1_epi16(128)), 8)));
}

inline __m512bh CVT_FP8_TO_BF16(__m256i a) {
#ifdef SGLANG_CPU_FP8_CVT_FTZ
  return cvt_e4m3_bf16_intrinsic_without_denorm(a);
#else
  return cvt_e4m3_bf16_intrinsic_with_denorm(a);
#endif
}

#endif

// vector to scalar reduction
#if defined(CPU_CAPABILITY_AVX512) && 0
inline float vec_reduce_sum(const Vectorized<float>& a) {
  return _mm512_reduce_add_ps(__m512(a));
}

inline float vec_reduce_max(const Vectorized<float>& a) {
  return _mm512_reduce_max_ps(__m512(a));
}
#else
inline float vec_reduce_sum(const Vectorized<float>& a) {
  return vec_reduce_all([](Vectorized<float>& x, Vectorized<float>& y) { return x + y; }, a);
}

inline float vec_reduce_max(const Vectorized<float>& a) {
  return vec_reduce_all([](Vectorized<float>& x, Vectorized<float>& y) { return maximum(x, y); }, a);
}
#endif

// https://github.com/InternLM/lmdeploy/blob/086481ed84b59bee3b8e4274e5fc69620040c048/lmdeploy/pytorch/kernels/cuda/w8a8_triton_kernels.py#L282
template <typename scalar_t>
inline void
quantize_row_int8(uint8_t* __restrict__ Aq, float& As, const scalar_t* __restrict__ A, int64_t K, float eps = 1e-7) {
  float amax = 0.f;  // absolute max
  for (int64_t k = 0; k < K; ++k) {
    const float val = static_cast<float>(A[k]);
    amax = std::max(amax, std::abs(val));
  }

  amax = std::max(amax, eps);
  const float scale = amax / 127;
  const float inv_scale = 127 / amax;

  for (int64_t k = 0; k < K; ++k) {
    const float val = static_cast<float>(A[k]) * inv_scale;
    Aq[k] = (uint8_t)(std::round(val)) + 128;
  }
  As = scale;
}

#if defined(CPU_CAPABILITY_AVX512)
template <>
inline void quantize_row_int8<at::BFloat16>(
    uint8_t* __restrict__ Aq, float& As, const at::BFloat16* __restrict__ A, int64_t K, float eps) {
  const __m512 signBit = _mm512_set1_ps(-0.0f);
  const __m512i off = _mm512_set1_epi32(128);

  // K is 32x, no remainder
  float amax = 0.f;
  __m512 vamax0 = _mm512_set1_ps(0.f);
  __m512 vamax1 = _mm512_set1_ps(0.f);
  for (int64_t k = 0; k < K; k += 32) {
    __m512i va = _mm512_loadu_si512((void*)(A + k));
    __m512 va0 = CVT_BF16_TO_FP32(_mm512_extracti32x8_epi32(va, 0));
    __m512 va1 = CVT_BF16_TO_FP32(_mm512_extracti32x8_epi32(va, 1));
    vamax0 = _mm512_max_ps(vamax0, _mm512_andnot_ps(signBit, va0));
    vamax1 = _mm512_max_ps(vamax1, _mm512_andnot_ps(signBit, va1));
  }
  amax = _mm512_reduce_max_ps(_mm512_max_ps(vamax0, vamax1));
  amax = std::max(amax, eps);
  const float scale = amax / 127;
  const float inv_scale = 127 / amax;
  const __m512 vd = _mm512_set1_ps(inv_scale);

  for (int64_t k = 0; k < K; k += 32) {
    __m512i va = _mm512_loadu_si512((void*)(A + k));
    __m512 va0 = CVT_BF16_TO_FP32(_mm512_extracti32x8_epi32(va, 0));
    __m512 va1 = CVT_BF16_TO_FP32(_mm512_extracti32x8_epi32(va, 1));
    va0 = _mm512_mul_ps(va0, vd);
    va1 = _mm512_mul_ps(va1, vd);
    va0 = _mm512_roundscale_ps(va0, (_MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC));
    va1 = _mm512_roundscale_ps(va1, (_MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC));
    __m128i i0 = _mm512_cvtepi32_epi8(_mm512_add_epi32(_mm512_cvtps_epi32(va0), off));
    __m128i i1 = _mm512_cvtepi32_epi8(_mm512_add_epi32(_mm512_cvtps_epi32(va1), off));
    _mm256_storeu_si256(reinterpret_cast<__m256i*>(Aq + k), _mm256_set_m128i(i1, i0));
  }
  As = scale;
}
#endif

}  // anonymous namespace