[CPU] Support int8 compute mode in CPU AWQ (#35697)

Signed-off-by: Yintong Lu <yintong.lu@intel.com>

.buildkite/hardware_tests/cpu.yaml

@@ -13,12 +13,14 @@ steps:
   - tests/kernels/attention/test_cpu_attn.py
   - tests/kernels/moe/test_cpu_fused_moe.py
   - tests/kernels/test_onednn.py
+  - tests/kernels/test_awq_int4_to_int8.py
   commands:
     - |
       bash .buildkite/scripts/hardware_ci/run-cpu-test.sh 20m "
       pytest -x -v -s tests/kernels/attention/test_cpu_attn.py
       pytest -x -v -s tests/kernels/moe/test_cpu_fused_moe.py
-      pytest -x -v -s tests/kernels/test_onednn.py"
+      pytest -x -v -s tests/kernels/test_onednn.py
+      pytest -x -v -s tests/kernels/test_awq_int4_to_int8.py"
 
 - label: CPU-Compatibility Tests
   depends_on: []

cmake/cpu_extension.cmake

@@ -373,6 +373,7 @@ if (ENABLE_X86_ISA)
         "csrc/cpu/sgl-kernels/gemm.cpp"
         "csrc/cpu/sgl-kernels/gemm_int8.cpp"
         "csrc/cpu/sgl-kernels/gemm_fp8.cpp"
+        "csrc/cpu/sgl-kernels/gemm_int4.cpp"
         "csrc/cpu/sgl-kernels/moe.cpp"
         "csrc/cpu/sgl-kernels/moe_int8.cpp"
         "csrc/cpu/sgl-kernels/moe_fp8.cpp")

csrc/cpu/sgl-kernels/common.h

@@ -117,6 +117,14 @@ inline void parallel_for(int n, const func_t& f) {
 #endif
 }
 
+inline int get_thread_num() {
+#if defined(_OPENMP)
+  return omp_get_thread_num();
+#else
+  return 0;
+#endif
+}
+
 // for 1d parallel, use `actual_nth`
 // for 2d parallel, use even nths, e.g. 43->42
 int inline adjust_num_threads(int m) {

csrc/cpu/sgl-kernels/gemm.h

@@ -17,8 +17,8 @@ constexpr int block_size_n() { return 2 * TILE_N; }
 template <typename T> inline bool can_use_brgemm(int M);
 template <> inline bool can_use_brgemm<at::BFloat16>(int M) { return M > 4; }
 template <> inline bool can_use_brgemm<at::Half>(int M) { return true; }
-// TODO: add u8s8 brgemm, this requires PyTorch 2.7
+template <> inline bool can_use_brgemm<int8_t>(int M) { return M > 4; }
-template <> inline bool can_use_brgemm<int8_t>(int M) { return false; }
+template <> inline bool can_use_brgemm<uint8_t>(int M) { return M > 4; }
 template <> inline bool can_use_brgemm<at::Float8_e4m3fn>(int M) { return M > 4; }
 template <> inline bool can_use_brgemm<at::quint4x2>(int M) { return M > 4; }
 
@@ -40,9 +40,17 @@ inline int64_t get_row_size(int64_t K, bool use_int8_w8a8) {
   return use_int8_w8a8 ? K + sizeof(int32_t) : K;
 }
 
-// pack weight to vnni format
+inline int64_t get_4bit_block_k_size(int64_t group_size) {
+  return group_size > 128 ? 128 : group_size;
+}
+
+// pack weight into vnni format
 at::Tensor convert_weight_packed(at::Tensor& weight);
 
+// pack weight to vnni format for int4 (adapted from sglang)
+std::tuple<at::Tensor, at::Tensor, at::Tensor>
+convert_weight_packed_scale_zp(at::Tensor qweight, at::Tensor qzeros, at::Tensor scales);
+
 // moe implementations for int8 w8a8
 template <typename scalar_t>
 void fused_experts_int8_kernel_impl(
@@ -233,6 +241,31 @@ void tinygemm_kernel(
     int64_t strideBs,
     bool brg);
 
+// int4 scaled GEMM (adapted from sglang)
+at::Tensor int4_scaled_mm_cpu(
+    at::Tensor& x, at::Tensor& w, at::Tensor& w_zeros, at::Tensor& w_scales, std::optional<at::Tensor> bias);
+
+// int4 tinygemm kernel interface(adapted from sglang)
+template <typename scalar_t>
+void tinygemm_kernel(
+    scalar_t* C,
+    float* C_temp,
+    const uint8_t* A,
+    const float* scales_a,
+    const int32_t* qzeros_a,
+    const uint8_t* B,
+    const float* scales_b,
+    const int8_t* qzeros_b,
+    const int32_t* compensation,
+    int8_t* dqB_tmp,
+    int64_t M,
+    int64_t K,
+    int64_t lda,
+    int64_t ldc_f,
+    int64_t ldc_s,
+    bool store_out,
+    bool use_brgemm);
+
 // TODO: debug print, remove me later
 inline void print_16x32i(const __m512i x) {
   int32_t a[16];

csrc/cpu/sgl-kernels/gemm_int4.cpp

@@ -0,0 +1,755 @@
+// SPDX-License-Identifier: Apache-2.0
+// Adapted from sgl-project/sglang
+// https://github.com/sgl-project/sglang/pull/8226
+
+#include <ATen/ATen.h>
+
+#include "common.h"
+#include "gemm.h"
+#include "vec.h"
+
+namespace {
+
+#define BLOCK_N block_size_n()
+#define BLOCK_M 128
+
+template <bool sym_quant_act>
+struct ActDtype;
+template <>
+struct ActDtype<true> {
+  using type = int8_t;
+};
+template <>
+struct ActDtype<false> {
+  using type = uint8_t;
+};
+
+struct alignas(32) m256i_wrapper {
+  __m256i data;
+};
+
+#if defined(CPU_CAPABILITY_AVX512)
+inline std::array<m256i_wrapper, 2> load_zps_4vnni(
+    const int8_t* __restrict__ zps) {
+  __m256i vzps_low = _mm256_set1_epi64x(*reinterpret_cast<const int64_t*>(zps));
+  __m256i vzps_high =
+      _mm256_set1_epi64x(*reinterpret_cast<const int64_t*>(zps + 8));
+  __m256i shuffle_mask =
+      _mm256_set_epi8(7, 7, 7, 7, 6, 6, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 3, 3, 3,
+                      3, 2, 2, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0);
+  vzps_low = _mm256_shuffle_epi8(vzps_low, shuffle_mask);
+  vzps_high = _mm256_shuffle_epi8(vzps_high, shuffle_mask);
+  m256i_wrapper vzps_low_wp, vzps_high_wp;
+  vzps_low_wp.data = vzps_low;
+  vzps_high_wp.data = vzps_high;
+  return {vzps_low_wp, vzps_high_wp};
+}
+
+inline std::array<m256i_wrapper, 2> load_uint4_as_int8(
+    const uint8_t* __restrict__ qB) {
+  __m256i packed = _mm256_loadu_si256(reinterpret_cast<const __m256i*>(qB));
+  const __m256i low_mask = _mm256_set1_epi8(0x0f);
+  __m256i high = _mm256_srli_epi16(packed, 4);
+  high = _mm256_and_si256(high, low_mask);
+  __m256i low = _mm256_and_si256(packed, low_mask);
+  m256i_wrapper low_wp, high_wp;
+  low_wp.data = low;
+  high_wp.data = high;
+  return {low_wp, high_wp};
+}
+
+template <int N, int ldb>
+void _dequant_weight_zp_only(const uint8_t* __restrict__ B, int8_t* dqB,
+                             const int8_t* __restrict__ qzeros, int64_t K) {
+  #pragma GCC unroll 2
+  for (int n = 0; n < N; n += 16) {
+    auto [zps_low_wp, zps_high_wp] = load_zps_4vnni(&qzeros[n]);
+    auto zps_low = zps_low_wp.data;
+    auto zps_high = zps_high_wp.data;
+    for (int k = 0; k < K; k += 4) {
+      auto [vb_low_wp, vb_high_wp] =
+          load_uint4_as_int8(B + ldb * k + n / 2 * 4);
+      auto vb_low = vb_low_wp.data;
+      auto vb_high = vb_high_wp.data;
+      vb_high = _mm256_sub_epi8(vb_high, zps_high);
+      vb_low = _mm256_sub_epi8(vb_low, zps_low);
+      _mm256_storeu_si256(reinterpret_cast<__m256i_u*>(dqB + N * k + n * 4),
+                          vb_low);
+      _mm256_storeu_si256(
+          reinterpret_cast<__m256i_u*>(dqB + N * k + (n + 8) * 4), vb_high);
+    }
+  }
+}
+
+template <bool sym_quant_act, int N, bool accum>
+void _dequant_and_store(float* __restrict__ output,
+                        const int32_t* __restrict__ input,
+                        const float* __restrict__ scale_a,
+                        const int32_t* __restrict__ zp_a,
+                        const float* __restrict__ scale_b,
+                        const int32_t* __restrict__ comp_b, int M, int ldi,
+                        int ldo, int ldsa = 1) {
+  for (int m = 0; m < M; ++m) {
+    float a_scale = *(scale_a + m * ldsa);
+    __m512 va_scale = _mm512_set1_ps(a_scale);
+    int32_t a_zp;
+    __m512i va_zp;
+    if constexpr (!sym_quant_act) {
+      a_zp = *(zp_a + m * ldsa);
+      va_zp = _mm512_set1_epi32(a_zp);
+    }
+    int n = 0;
+  #pragma GCC unroll 2
+    for (; n < N; n += 16) {
+      __m512i vc = _mm512_loadu_si512(input + m * ldi + n);
+      if constexpr (!sym_quant_act) {
+        __m512i vb_comp = _mm512_loadu_si512(comp_b + n);
+        vc = _mm512_sub_epi32(vc, _mm512_mullo_epi32(vb_comp, va_zp));
+      }
+      __m512 vc_f = _mm512_cvtepi32_ps(vc);
+      __m512 vc_f_mul = _mm512_mul_ps(vc_f, va_scale);
+      __m512 vb_s = _mm512_loadu_ps(scale_b + n);
+      vc_f_mul = _mm512_mul_ps(vc_f_mul, vb_s);
+      if constexpr (accum) {
+        __m512 vo = _mm512_loadu_ps(output + m * ldo + n);
+        _mm512_storeu_ps(output + m * ldo + n, _mm512_add_ps(vo, vc_f_mul));
+      } else {
+        _mm512_storeu_ps(output + m * ldo + n, vc_f_mul);
+      }
+    }
+    for (; n < N; ++n) {
+      float dq_val;
+      if constexpr (sym_quant_act) {
+        dq_val = (float)input[m * ldi + n] * a_scale * scale_b[n];
+      } else {
+        dq_val = (float)(input[m * ldi + n] - a_zp * comp_b[n]) * a_scale *
+                 scale_b[n];
+      }
+      if constexpr (accum) {
+        output[m * ldo + n] += dq_val;
+      } else {
+        output[m * ldo + n] = dq_val;
+      }
+    }
+  }
+}
+
+#else
+template <int N, int ldb>
+void _dequant_weight_zp_only(const uint8_t* B, int8_t* dqB,
+                             const int8_t* qzeros, int64_t K) {
+  for (int k = 0; k < K; ++k) {
+    for (int n = 0; n < N / 2; ++n) {
+      int32_t b = (int32_t)B[k * ldb + n];
+      dqB[k * N + n * 2] = (b & 0xf) - qzeros[n];
+      dqB[k * N + n * 2 + 1] = (b >> 4) - qzeros[n];
+    }
+  }
+}
+#endif
+
+#if defined(CPU_CAPABILITY_AVX512)
+inline __m512i combine_m256i(__m256i a, __m256i b) {
+  __m512i c = _mm512_castsi256_si512(a);
+  return _mm512_inserti64x4(c, b, 1);
+}
+
+inline __m512i combine_m256i(std::array<m256i_wrapper, 2> two_256) {
+  return combine_m256i(two_256[0].data, two_256[1].data);
+}
+
+static inline __m512i _mm512_sign_epi8(__m512i a, __m512i b) {
+  __m512i zero = _mm512_setzero_si512();
+  __mmask64 blt0 = _mm512_movepi8_mask(b);
+  return _mm512_mask_sub_epi8(a, blt0, zero, a);
+}
+
+template <bool sym_quant_act, int M, int N, int ldb>
+void _dequant_gemm_accum_small_M(float* __restrict__ C, const uint8_t* A,
+                                 const float* scales_a, const int32_t* qzeros_a,
+                                 const uint8_t* B, const float* scales_b,
+                                 const int8_t* qzeros_b, int64_t K, int64_t lda,
+                                 int64_t ldc) {
+  constexpr int COLS = N / 16;
+  __m512i ones = _mm512_set1_epi8(1);
+  __m512i va;
+  __m512i vb[COLS];
+  __m512i vc[M * COLS];
+  __m512 vscales[COLS];
+  __m512i vzps[COLS];
+  __m512i vcompensate[COLS];
+
+  Unroll<COLS>{}([&](auto i) {
+    vscales[i] = _mm512_loadu_ps(scales_b + i * 16);
+    vzps[i] = combine_m256i(load_zps_4vnni(qzeros_b + i * 16));
+    if constexpr (!sym_quant_act) {
+      vcompensate[i] = _mm512_setzero_epi32();
+    }
+  });
+  Unroll<M * COLS>{}([&](auto i) { vc[i] = _mm512_setzero_epi32(); });
+
+  auto compute = [&](auto i, int k) {
+    constexpr const int row = i / COLS;
+    constexpr const int col = i % COLS;
+
+    if constexpr (col == 0) {
+      va = _mm512_set1_epi32(*(int32_t*)(A + row * lda + k));
+    }
+
+    if constexpr (row == 0) {
+      int B_offset = k * ldb + col * 16 * 2;
+      vb[col] = combine_m256i(load_uint4_as_int8(B + B_offset));
+      vb[col] = _mm512_sub_epi8(vb[col], vzps[col]);
+      if constexpr (!sym_quant_act) {
+        vcompensate[col] = _mm512_dpbusd_epi32(vcompensate[col], ones, vb[col]);
+      }
+      _mm_prefetch(B + B_offset + 128 * ldb, _MM_HINT_T0);
+    }
+    if constexpr (sym_quant_act) {
+      auto vsb = _mm512_sign_epi8(vb[col], va);
+      auto vabsa = _mm512_sign_epi8(va, va);
+      vc[i] = _mm512_dpbusds_epi32(vc[i], vabsa, vsb);
+    } else {
+      vc[i] = _mm512_dpbusd_epi32(vc[i], va, vb[col]);
+    }
+  };
+
+  constexpr const int unroll = 4;
+  int k = 0;
+  for (; k < K / 4 / unroll; k++) {
+    Unroll<unroll>{}(
+        [&](auto i) { Unroll<M * COLS>{}(compute, 4 * (k * unroll + i)); });
+  }
+  k *= 4 * unroll;
+  for (; k < K; k += 4) {
+    Unroll<M * COLS>{}(compute, k);
+  }
+
+  auto store = [&](auto i) {
+    constexpr const int row = i / COLS;
+    constexpr const int col = i % COLS;
+    __m512 vc_float;
+    if constexpr (!sym_quant_act) {
+      vc[i] = _mm512_sub_epi32(
+          vc[i], _mm512_mullo_epi32(vcompensate[col],
+                                    _mm512_set1_epi32(*(qzeros_a + row))));
+    }
+    vc_float = _mm512_cvtepi32_ps(vc[i]);
+    vc_float = _mm512_mul_ps(vc_float, _mm512_set1_ps(*(scales_a + row)));
+
+    vc_float = _mm512_mul_ps(vc_float, vscales[col]);
+    auto vc_old = _mm512_loadu_ps(C + row * ldc + col * 16);
+    vc_float = _mm512_add_ps(vc_float, vc_old);
+    _mm512_storeu_ps(C + row * ldc + col * 16, vc_float);
+  };
+  Unroll<M * COLS>{}(store);
+}
+
+  #define CALL_DEQUANT_GEMM_ACCUM_SMALL_M(M)               \
+    _dequant_gemm_accum_small_M<sym_quant_act, M, N, ldb>( \
+        C, A, scales_a, qzeros_a, B, scales_b, qzeros_b, K, lda, ldc);
+#endif
+
+template <bool sym_quant_act, int N, int ldb>
+void _dequant_gemm_accum(float* C, const uint8_t* A, const float* scales_a,
+                         const int32_t* qzeros_a, const uint8_t* B,
+                         const float* scales_b, const int8_t* qzeros_b,
+                         const int32_t* compensation, int8_t* dqB, int64_t M,
+                         int64_t K, int64_t lda, int64_t ldc, bool use_brgemm) {
+#if defined(CPU_CAPABILITY_AVX512)
+  if (!use_brgemm) {
+    switch (M) {
+      case 1:
+        CALL_DEQUANT_GEMM_ACCUM_SMALL_M(1);
+        break;
+      case 2:
+        CALL_DEQUANT_GEMM_ACCUM_SMALL_M(2);
+        break;
+      case 3:
+        CALL_DEQUANT_GEMM_ACCUM_SMALL_M(3);
+        break;
+      case 4:
+        CALL_DEQUANT_GEMM_ACCUM_SMALL_M(4);
+        break;
+      default:
+        TORCH_CHECK(false, "tinygemm_kernel: unexpected M for AVX path!");
+    }
+    return;
+  }
+
+  _dequant_weight_zp_only<N, ldb>(B, dqB, qzeros_b, K);
+  using Tin = typename ActDtype<sym_quant_act>::type;
+  Tin* A_ptr = (Tin*)A;
+  if (use_brgemm) {
+    int32_t C_i32[M * N];
+    at::native::cpublas::brgemm(M, N, K, lda, N /*ldb*/, N /*ldc*/,
+                                false /* add_C */, A_ptr, dqB, C_i32,
+                                true /* is_vnni */);
+    _mm_prefetch(B + N * K / 2, _MM_HINT_T0);
+    _mm_prefetch(A + K, _MM_HINT_T0);
+    _dequant_and_store<sym_quant_act, N, true>(C, C_i32, scales_a, qzeros_a,
+                                               scales_b, compensation, M,
+                                               N /*ldi*/, ldc, 1 /*ldsa*/);
+  } else
+#endif
+  {
+    TORCH_CHECK(false, "tinygemm_kernel: scalar path not implemented!");
+  }
+}
+
+template <int N>
+inline void copy_bias(const float* bias_ptr, float* y_buf, int64_t m) {
+  if (bias_ptr) {
+    for (int i = 0; i < m; ++i) {
+      int j = 0;
+#if defined(CPU_CAPABILITY_AVX512)
+  #pragma GCC unroll 2
+      for (; j < N; j += 16) {
+        __m512 bias_vec = _mm512_loadu_ps(bias_ptr + j);
+        _mm512_storeu_ps(y_buf + i * N + j, bias_vec);
+      }
+#endif
+      for (; j < N; ++j) {
+        y_buf[i * N + j] = bias_ptr[j];
+      }
+    }
+  } else {
+    for (int i = 0; i < m; ++i) {
+      int j = 0;
+#if defined(CPU_CAPABILITY_AVX512)
+  #pragma GCC unroll 2
+      for (; j < N; j += 16) {
+        __m512 zero_vec = _mm512_setzero_ps();
+        _mm512_storeu_ps(y_buf + i * N + j, zero_vec);
+      }
+#endif
+      for (; j < N; ++j) {
+        y_buf[i * N + j] = 0;
+      }
+    }
+  }
+}
+
+template <int N, typename out_dtype>
+inline void store_out(const float* y_buf, out_dtype* c_ptr, int64_t m,
+                      int64_t lda) {
+  for (int i = 0; i < m; ++i) {
+    int j = 0;
+    if constexpr (std::is_same<out_dtype, float>::value) {
+#if defined(CPU_CAPABILITY_AVX512)
+  #pragma GCC unroll 2
+      for (; j < N; j += 16) {
+        __m512 y_vec = _mm512_loadu_ps(y_buf + i * N + j);
+        _mm512_storeu_ps(c_ptr + i * lda + j, y_vec);
+      }
+#endif
+      for (; j < N; ++j) {
+        c_ptr[i * lda + j] = y_buf[i * N + j];
+      }
+    } else if constexpr (std::is_same<out_dtype, at::BFloat16>::value) {
+#if defined(CPU_CAPABILITY_AVX512)
+  #pragma GCC unroll 2
+      for (; j < N; j += 16) {
+        __m512 y_vec = _mm512_loadu_ps(y_buf + i * N + j);
+        __m256i y_bf16_vec = at::vec::cvtfp32_bf16(y_vec);
+        _mm256_storeu_si256(reinterpret_cast<__m256i*>(c_ptr + i * lda + j),
+                            y_bf16_vec);
+      }
+#endif
+      for (; j < N; ++j) {
+        c_ptr[i * lda + j] = at::BFloat16(y_buf[i * N + j]);
+      }
+    } else if constexpr (std::is_same<out_dtype, at::Half>::value) {
+#if defined(CPU_CAPABILITY_AVX512)
+  #pragma GCC unroll 2
+      for (; j < N; j += 16) {
+        __m512 y_vec = _mm512_loadu_ps(y_buf + i * N + j);
+        __m256i y_fp16_vec = at::vec::cvtfp32_fp16(y_vec);
+        _mm256_storeu_si256(reinterpret_cast<__m256i*>(c_ptr + i * lda + j),
+                            y_fp16_vec);
+      }
+#endif
+      for (; j < N; ++j) {
+        c_ptr[i * lda + j] = at::Half(y_buf[i * N + j]);
+      }
+    } else {
+      TORCH_CHECK(false, "Unsupported output dtype");
+    }
+  }
+}
+
+void fill_val_stub(int32_t* __restrict__ output, int32_t value, int64_t size) {
+  using iVec = at::vec::Vectorized<int32_t>;
+  constexpr int VecSize = iVec::size();
+  const iVec fill_val_vec = iVec(value);
+  int64_t d;
+#pragma GCC unroll 4
+  for (d = 0; d <= size - VecSize; d += VecSize) {
+    fill_val_vec.store(output + d);
+  }
+  for (; d < size; ++d) {
+    output[d] = value;
+  }
+}
+
+template <bool sym_quant_act, typename act_dtype, typename out_dtype>
+void _da8w4_linear_impl(
+    act_dtype* __restrict__ input, const float* __restrict__ input_scales,
+    const int32_t* __restrict__ input_qzeros,
+    const uint8_t* __restrict__ weight, const float* __restrict__ weight_scales,
+    const int8_t* __restrict__ weight_qzeros, const float* __restrict__ bias,
+    out_dtype* __restrict__ output, float* __restrict__ output_temp,
+    int8_t* __restrict__ dequant_weight_temp, int64_t M, int64_t N, int64_t K,
+    int64_t num_groups) {
+  const bool use_brgemm = can_use_brgemm<act_dtype>(M);
+  int64_t block_m = [&]() -> long {
+    if (M <= 48) {
+      return M;
+    } else if (M < 64) {
+      return 32;
+    } else if (M < 96) {
+      return 64;
+    } else {
+      return 128;
+    }
+  }();
+  int64_t Mc = div_up(M, block_m);
+  bool parallel_on_M = M > 128;
+  int64_t Nc = N / BLOCK_N;
+  int64_t num_blocks = parallel_on_M ? Mc * Nc : Nc;
+  int64_t group_size = div_up(K, num_groups);
+  int64_t _block_k = get_4bit_block_k_size(group_size);
+  int64_t Kc = K / _block_k;
+  int64_t block_per_group = group_size / _block_k;
+
+  at::parallel_for(0, num_blocks, 1, [&](int64_t begin, int64_t end) {
+    int tid = get_thread_num();
+    float* C_tmp = output_temp + tid * block_m * BLOCK_N;
+    int8_t* dqB_tmp = dequant_weight_temp + tid * _block_k * BLOCK_N;
+    for (const auto i : c10::irange(begin, end)) {
+      int64_t mc = parallel_on_M ? i / Nc : 0;
+      int64_t nc = parallel_on_M ? i % Nc : i;
+      int64_t mc_end = parallel_on_M ? mc + 1 : Mc;
+
+      for (int mci = mc; mci < mc_end; ++mci) {
+        int64_t m_size =
+            mci * block_m + block_m > M ? M - mci * block_m : block_m;
+        auto bias_data = bias ? bias + nc * BLOCK_N : nullptr;
+        copy_bias<BLOCK_N>(bias_data, C_tmp, m_size);
+        for (int kci = 0; kci < Kc; ++kci) {
+          int32_t* compensation_ptr =
+              sym_quant_act
+                  ? nullptr
+                  : (int32_t*)(void*)(weight +
+                                      (nc * Kc + kci) *
+                                          (BLOCK_N *
+                                           (_block_k / 2 + sizeof(int32_t))) +
+                                      _block_k * BLOCK_N / 2);
+          _dequant_gemm_accum<sym_quant_act, BLOCK_N, BLOCK_N / 2>(
+              /*C*/ C_tmp,
+              /*A*/ (uint8_t*)input + mci * block_m * K + kci * _block_k,
+              /*scales_a*/ input_scales + mci * block_m,
+              /*qzeros_a*/ input_qzeros + mci * block_m,
+              /*B*/ weight + (nc * Kc + kci) *
+                                 (BLOCK_N * (_block_k / 2 + sizeof(int32_t))),
+              /*scales_b*/ weight_scales + nc * BLOCK_N * num_groups +
+                  kci / block_per_group * BLOCK_N,
+              /*qzeros_b*/ weight_qzeros + nc * BLOCK_N * num_groups +
+                  kci / block_per_group * BLOCK_N,
+              /*Bcomp*/ compensation_ptr,
+              /*dqB_tmp*/ dqB_tmp,
+              /*M*/ m_size,
+              /*K*/ _block_k,
+              /*lda*/ K,
+              /*ldc*/ BLOCK_N,
+              /*use_brgemm*/ use_brgemm);
+        }
+        store_out<BLOCK_N>(C_tmp, output + mci * block_m * N + nc * BLOCK_N,
+                           m_size, N /*lda*/);
+      }
+    }
+    if (use_brgemm) {
+      at::native::cpublas::brgemm_release();
+    }
+  });
+}
+
+}  // anonymous namespace
+
+std::tuple<at::Tensor, at::Tensor, at::Tensor>
+convert_int4_weight_packed_with_compensation(const at::Tensor& weight,
+                                             const at::Tensor& scales,
+                                             const at::Tensor& qzeros) {
+  TORCH_CHECK(weight.dim() == 2,
+              "DA8W4 CPU: Weight should be a 2D tensor for packing");
+  TORCH_CHECK(
+      weight.size(1) % 2 == 0,
+      "DA8W4 CPU: Weight should have even number of columns for packing");
+
+  auto new_scales = scales;
+  auto new_qzeros = qzeros;
+  if (new_scales.dim() == 1) {
+    new_scales.unsqueeze_(1);
+  }
+  new_scales = new_scales.to(at::kFloat);
+  if (new_qzeros.dim() == 1) {
+    new_qzeros.unsqueeze_(1);
+  }
+  new_qzeros = new_qzeros.to(at::kChar);
+  int64_t N = weight.size(0);
+  int64_t K = weight.size(1);
+  int64_t G = scales.size(1);
+  int64_t group_size = K / G;
+  int64_t _block_k = get_4bit_block_k_size(group_size);
+  constexpr int block_n = block_size_n();
+  int64_t Nc = N / block_n;
+  int64_t Kc = K / _block_k;
+
+  auto weight_view = weight.view({Nc, block_n, Kc, _block_k});
+  at::Tensor weight_reordered = weight_view.permute({0, 2, 3, 1}).contiguous();
+  at::Tensor blocked_weight;
+  at::Tensor blocked_scales =
+      new_scales.view({Nc, block_n, G}).permute({0, 2, 1}).contiguous();
+  at::Tensor blocked_qzeros =
+      new_qzeros.view({Nc, block_n, G}).permute({0, 2, 1}).contiguous();
+  auto weight_sub_qzero = weight.view({Nc, block_n, G, -1}).to(at::kInt) -
+                          new_qzeros.view({Nc, block_n, G, -1});
+  weight_sub_qzero = weight_sub_qzero.view({Nc, block_n, Kc, _block_k});
+  at::Tensor compensation = weight_sub_qzero.sum(-1);
+  compensation = compensation.permute({0, 2, 1}).contiguous().to(at::kInt);
+  int64_t buffer_size_nbytes =
+      _block_k * block_n / 2 + block_n * sizeof(int32_t);
+  blocked_weight = at::empty({Nc, Kc, buffer_size_nbytes}, weight.options());
+
+  auto weight_ptr = weight_reordered.data_ptr<uint8_t>();
+  auto compensation_ptr = compensation.data_ptr<int32_t>();
+  auto blocked_weight_ptr = blocked_weight.data_ptr<uint8_t>();
+  int64_t num_blocks = Nc * Kc;
+  at::parallel_for(0, num_blocks, 1, [&](int64_t begin, int64_t end) {
+    for (const auto i : c10::irange(begin, end)) {
+      auto in_ptr = weight_ptr + i * _block_k * block_n;
+      auto out_ptr =
+          blocked_weight_ptr + i * block_n * (_block_k / 2 + sizeof(int32_t));
+      int32_t* comp_in_prt = compensation_ptr + i * block_n;
+      int32_t* comp_out_prt =
+          (int32_t*)(void*)(blocked_weight_ptr +
+                            i * block_n * (_block_k / 2 + sizeof(int32_t)) +
+                            _block_k * block_n / 2);
+      constexpr int n_group_size = 8;
+      constexpr int vnni_size = 4;
+      constexpr int n_group = block_n / n_group_size;
+      for (int nb = 0; nb < n_group; nb += 2) {
+        for (int k = 0; k < _block_k; k += vnni_size) {
+          for (int ni = 0; ni < n_group_size; ++ni) {
+            for (int ki = 0; ki < vnni_size; ++ki) {
+              int src_idx_1 = nb * n_group_size + ni + (k + ki) * block_n;
+              int src_idx_2 = (nb + 1) * n_group_size + ni + (k + ki) * block_n;
+              int dst_idx = (nb / 2 * n_group_size + ni) * vnni_size +
+                            k * block_n / 2 + ki;
+              uint8_t src_1 = *(in_ptr + src_idx_1);
+              uint8_t src_2 = *(in_ptr + src_idx_2);
+              uint8_t dst = (src_1 & 0x0f) | ((src_2 & 0x0f) << 4);
+              *(out_ptr + dst_idx) = dst;
+            }
+          }
+        }
+      }
+      for (int nb = 0; nb < block_n; nb++) {
+        *(comp_out_prt + nb) = *(comp_in_prt + nb);
+      }
+    }
+  });
+
+  return std::make_tuple(std::move(blocked_weight), std::move(blocked_scales),
+                         std::move(blocked_qzeros));
+}
+
+std::tuple<at::Tensor, at::Tensor> autoawq_to_int4pack(at::Tensor qweight,
+                                                       at::Tensor qzeros) {
+  auto bitshifts = at::tensor({0, 4, 1, 5, 2, 6, 3, 7}, at::kInt) * 4;
+  auto qweight_unsq = qweight.unsqueeze(-1);
+  auto unpacked = at::bitwise_right_shift(qweight_unsq, bitshifts) & 0xF;
+  auto qweight_final = unpacked.flatten(-2).transpose(-1, -2).to(at::kByte);
+
+  auto qzeros_unsq = qzeros.unsqueeze(-1);
+  auto qzeros_unpacked = at::bitwise_right_shift(qzeros_unsq, bitshifts) & 0xF;
+  auto qzeros_final = qzeros_unpacked.flatten(-2).to(at::kByte);
+
+  return std::make_tuple(qweight_final, qzeros_final);
+}
+
+std::tuple<at::Tensor, at::Tensor, at::Tensor> convert_weight_packed_scale_zp(
+    at::Tensor qweight, at::Tensor qzeros, at::Tensor scales) {
+  auto res = autoawq_to_int4pack(qweight, qzeros);
+  auto _qweight = std::get<0>(res);
+  auto _qzeros = std::get<1>(res);
+  auto _scales = scales;
+  _qzeros = _qzeros.transpose(-2, -1).contiguous();
+  _scales = _scales.transpose(-2, -1).contiguous();
+  if (_qweight.dim() == 3) {
+    int64_t E = _qweight.size(0);
+    int64_t K = _qweight.size(2);
+    int64_t G = _scales.size(2);
+    int64_t group_size = K / G;
+    int64_t _block_k = get_4bit_block_k_size(group_size);
+    int64_t block_n = block_size_n();
+    int64_t Nc = _qweight.size(1) / block_n;
+    int64_t Kc = K / _block_k;
+    int64_t buffer_size_nbytes =
+        _block_k * block_n / 2 + block_n * sizeof(int32_t);
+    auto blocked_weight =
+        at::empty({E, Nc, Kc, buffer_size_nbytes}, _qweight.options());
+    auto blocked_scales =
+        at::empty({E, Nc, G, block_n}, _scales.options()).to(at::kFloat);
+    auto blocked_qzeros =
+        at::empty({E, Nc, G, block_n}, _qzeros.options()).to(at::kChar);
+    for (int i = 0; i < _qweight.size(0); i++) {
+      auto res_ = convert_int4_weight_packed_with_compensation(
+          _qweight[i], _scales[i], _qzeros[i]);
+      blocked_weight[i] = std::get<0>(res_);
+      blocked_scales[i] = std::get<1>(res_);
+      blocked_qzeros[i] = std::get<2>(res_);
+    }
+    _qweight = blocked_weight;
+    _scales = blocked_scales;
+    _qzeros = blocked_qzeros;
+  } else {
+    auto res_ = convert_int4_weight_packed_with_compensation(_qweight, _scales,
+                                                             _qzeros);
+    _qweight = std::get<0>(res_);
+    _scales = std::get<1>(res_);
+    _qzeros = std::get<2>(res_);
+  }
+
+  return std::make_tuple(_qweight, _qzeros, _scales);
+}
+
+at::Tensor int4_scaled_mm_cpu_with_quant(const at::Tensor& input,
+                                         const at::Tensor& weight,
+                                         const at::Tensor& weight_scales,
+                                         const at::Tensor& weight_qzeros,
+                                         const std::optional<at::Tensor>& bias,
+                                         at::ScalarType output_dtype) {
+  RECORD_FUNCTION("vllm::int4_scaled_mm_cpu_with_quant",
+                  std::vector<c10::IValue>({input, weight}));
+
+  int64_t M_a = input.size(0);
+  int64_t K_a = input.size(1);
+  int64_t lda = input.stride(0);
+
+  const auto st = input.scalar_type();
+  TORCH_CHECK(
+      st == at::kBFloat16 || st == at::kHalf,
+      "int4_scaled_mm_cpu_with_quant: expect A to be bfloat16 or half.");
+
+  constexpr bool sym_quant_act = false;
+  using Tin = typename ActDtype<sym_quant_act>::type;
+  int64_t act_buffer_size =
+      M_a * K_a + M_a * sizeof(float) + M_a * sizeof(int32_t);
+  auto act_buffer =
+      at::empty({act_buffer_size}, input.options().dtype(at::kByte));
+  auto Aq_data = act_buffer.data_ptr<uint8_t>();
+  auto As_data = reinterpret_cast<float*>(Aq_data + M_a * K_a);
+  auto Azp_data = reinterpret_cast<int32_t*>(As_data + M_a);
+  fill_val_stub(Azp_data, 128, M_a);
+
+  auto out_sizes = input.sizes().vec();
+  int64_t N = weight_scales.size(0) * weight_scales.size(-1);
+  out_sizes.back() = N;
+  auto output = at::empty(out_sizes, input.options());
+  int64_t Nc = weight.size(0);
+  int64_t Kc = weight.size(1);
+  int64_t _block_k = K_a / Kc;
+  TORCH_CHECK(N == Nc * BLOCK_N, "DA8W4: weight and input shapes mismatch");
+  int64_t num_groups = weight_scales.size(1);
+
+  const uint8_t* b_ptr = weight.data_ptr<uint8_t>();
+  const float* b_scales_ptr = weight_scales.data_ptr<float>();
+  const int8_t* b_qzeros_ptr = weight_qzeros.data_ptr<int8_t>();
+  const float* bias_ptr =
+      bias.has_value() ? bias.value().data_ptr<float>() : nullptr;
+  int num_threads = at::get_num_threads();
+  int64_t temp_buffer_size = num_threads * BLOCK_M * BLOCK_N * sizeof(float) +
+                             num_threads * _block_k * BLOCK_N;
+  auto c_temp_buffer =
+      at::empty({temp_buffer_size}, input.options().dtype(at::kChar));
+  float* c_temp_ptr = (float*)((void*)(c_temp_buffer.data_ptr<int8_t>()));
+  int8_t* dqB_temp_ptr =
+      (int8_t*)((void*)(c_temp_ptr + num_threads * BLOCK_M * BLOCK_N));
+
+#define LAUNCH_DA8W4_LINEAR_WITH_QUANT_IMPL(sym_quant_act)                 \
+  AT_DISPATCH_FLOATING_TYPES_AND2(                                         \
+      at::ScalarType::BFloat16, at::ScalarType::Half, output_dtype,        \
+      "int4_scaled_mm_cpu", [&] {                                          \
+        const scalar_t* __restrict__ A_data = input.data_ptr<scalar_t>();  \
+        scalar_t* __restrict__ c_ptr = output.data_ptr<scalar_t>();        \
+        at::parallel_for(0, M_a, 0, [&](int64_t begin, int64_t end) {      \
+          for (int64_t m = begin; m < end; ++m) {                          \
+            quantize_row_int8<scalar_t>(Aq_data + m * K_a, As_data[m],     \
+                                        A_data + m * lda, K_a);            \
+          }                                                                \
+        });                                                                \
+        _da8w4_linear_impl<sym_quant_act, Tin, scalar_t>(                  \
+            Aq_data, As_data, Azp_data, b_ptr, b_scales_ptr, b_qzeros_ptr, \
+            bias_ptr, c_ptr, c_temp_ptr, dqB_temp_ptr, M_a, N, K_a,        \
+            num_groups);                                                   \
+      });
+
+  LAUNCH_DA8W4_LINEAR_WITH_QUANT_IMPL(sym_quant_act);
+
+  return output;
+}
+
+namespace {
+
+template <typename scalar_t>
+inline void copy_stub(scalar_t* __restrict__ out,
+                      const float* __restrict__ input, int64_t size) {
+  using Vec = at::vec::Vectorized<scalar_t>;
+  using fVec = at::vec::Vectorized<float>;
+#pragma GCC unroll 4
+  for (int64_t d = 0; d < size; d += Vec::size()) {
+    fVec x0 = fVec::loadu(input + d);
+    fVec x1 = fVec::loadu(input + d + fVec::size());
+    Vec res = convert_from_float_ext<scalar_t>(x0, x1);
+    res.store(out + d);
+  }
+}
+
+}  // anonymous namespace
+
+template <typename scalar_t>
+void tinygemm_kernel(scalar_t* C, float* C_temp, const uint8_t* A,
+                     const float* scales_a, const int32_t* qzeros_a,
+                     const uint8_t* B, const float* scales_b,
+                     const int8_t* qzeros_b, const int32_t* compensation,
+                     int8_t* dqB_tmp, int64_t M, int64_t K, int64_t lda,
+                     int64_t ldc_f, int64_t ldc_s, bool store_out,
+                     bool use_brgemm) {
+  _dequant_gemm_accum<false, BLOCK_N, BLOCK_N / 2>(
+      C_temp, A, scales_a, qzeros_a, B, scales_b, qzeros_b, compensation,
+      dqB_tmp, M, K, lda, ldc_f, use_brgemm);
+  if (store_out) {
+    for (int64_t m = 0; m < M; ++m) {
+      copy_stub<scalar_t>(C + m * ldc_s, C_temp + m * ldc_f, BLOCK_N);
+    }
+  }
+}
+
+#define INSTANTIATE_TINYGEMM_TEMPLATE(TYPE)                                 \
+  template void tinygemm_kernel<TYPE>(                                      \
+      TYPE * C, float* C_temp, const uint8_t* A, const float* scales_a,     \
+      const int32_t* qzeros_a, const uint8_t* B, const float* scales_b,     \
+      const int8_t* qzeros_b, const int32_t* compensation, int8_t* dqB_tmp, \
+      int64_t M, int64_t K, int64_t lda, int64_t ldc_f, int64_t ldc_s,      \
+      bool store_out, bool use_brgemm)
+
+INSTANTIATE_TINYGEMM_TEMPLATE(at::BFloat16);
+INSTANTIATE_TINYGEMM_TEMPLATE(at::Half);
+
+at::Tensor int4_scaled_mm_cpu(at::Tensor& x, at::Tensor& w, at::Tensor& w_zeros,
+                              at::Tensor& w_scales,
+                              std::optional<at::Tensor> bias) {
+  return int4_scaled_mm_cpu_with_quant(x, w, w_scales, w_zeros, bias,
+                                       x.scalar_type());
+}

csrc/cpu/torch_bindings.cpp

@@ -79,6 +79,14 @@ at::Tensor int8_scaled_mm_with_quant(at::Tensor& mat1, at::Tensor& mat2,
                                      const std::optional<at::Tensor>& bias,
                                      at::ScalarType out_dtype, bool is_vnni);
 
+// Adapted from sglang: INT4 W4A8 kernels
+std::tuple<at::Tensor, at::Tensor, at::Tensor> convert_weight_packed_scale_zp(
+    at::Tensor qweight, at::Tensor qzeros, at::Tensor scales);
+
+at::Tensor int4_scaled_mm_cpu(at::Tensor& x, at::Tensor& w, at::Tensor& w_zeros,
+                              at::Tensor& w_scales,
+                              std::optional<at::Tensor> bias);
+
 torch::Tensor get_scheduler_metadata(
     const int64_t num_req, const int64_t num_heads_q,
     const int64_t num_heads_kv, const int64_t head_dim,
@@ -285,6 +293,18 @@ TORCH_LIBRARY_EXPAND(TORCH_EXTENSION_NAME, ops) {
       "Tensor? bias, ScalarType out_dtype, bool is_vnni) -> Tensor");
   ops.impl("int8_scaled_mm_with_quant", torch::kCPU,
            &int8_scaled_mm_with_quant);
+
+  // Adapted from sglang: INT4 W4A8 kernels
+  ops.def(
+      "convert_weight_packed_scale_zp(Tensor qweight, Tensor qzeros, "
+      "Tensor scales) -> (Tensor, Tensor, Tensor)");
+  ops.impl("convert_weight_packed_scale_zp", torch::kCPU,
+           &convert_weight_packed_scale_zp);
+
+  ops.def(
+      "int4_scaled_mm_cpu(Tensor(a0!) x, Tensor(a1!) w, Tensor(a2!) w_zeros, "
+      "Tensor(a3!) w_scales, Tensor? bias) -> Tensor");
+  ops.impl("int4_scaled_mm_cpu", torch::kCPU, &int4_scaled_mm_cpu);
 #endif
 
   // CPU attention kernels

tests/kernels/test_awq_int4_to_int8.py

@@ -0,0 +1,281 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""
+Unit tests for AWQ INT4 W4A8 GEMM pipeline (SGLang kernel migration).
+
+Part 1: Weight packing tests
+  - convert_weight_packed_scale_zp correctness
+
+Part 2: INT4 W4A8 GEMM tests
+  - int4_scaled_mm_cpu correctness w.r.t. float reference
+  - Bias, 3D input, various shapes
+
+Part 3: create_weights shapes
+
+cmd:
+    VLLM_CPU_INT4_W4A8=1 python -m pytest tests/kernels/test_awq_int4_to_int8.py -v -s
+"""
+
+import numpy as np
+import pytest
+import torch
+
+from vllm._custom_ops import _supports_cpu_w4a8_int8
+from vllm.model_executor.layers.quantization.utils.quant_utils import (
+    pack_cols,
+)
+from vllm.platforms import current_platform
+
+if not current_platform.is_cpu():
+    pytest.skip("skipping CPU-only tests", allow_module_level=True)
+
+requires_cpu_w4a8_int8 = pytest.mark.skipif(
+    not _supports_cpu_w4a8_int8,
+    reason="Requires vLLM CPU build with SGLang INT4 W4A8 kernels",
+)
+
+
+def make_awq_checkpoint_data(K, N, group_size, seed=42):
+    """Create synthetic AWQ checkpoint data in packed int32 format.
+
+    Returns:
+        packed_qweight: [K, N//8] int32 (AWQ interleaved + packed)
+        packed_qzeros:  [num_groups, N//8] int32 (AWQ interleaved + packed)
+        scales:         [num_groups, N] float32
+        float_ref:      [K, N] float32, reference dequantized weights
+        weight_int4_orig: [K, N] int32, original int4 values (0-15)
+        zeros_int4_orig:  [num_groups, N] int32, original zero points (0-15)
+    """
+    rng = np.random.RandomState(seed)
+    num_groups = K // group_size
+
+    weight_int4_orig = torch.from_numpy(
+        rng.randint(0, 16, size=(K, N)).astype(np.int32)
+    )
+    zeros_int4_orig = torch.from_numpy(
+        rng.randint(0, 16, size=(num_groups, N)).astype(np.int32)
+    )
+    scales = torch.from_numpy((rng.randn(num_groups, N) * 0.05).astype(np.float32))
+
+    scales_exp = scales.repeat_interleave(group_size, dim=0)
+    zeros_exp = zeros_int4_orig.repeat_interleave(group_size, dim=0)
+    float_ref = (weight_int4_orig.float() - zeros_exp.float()) * scales_exp
+
+    awq_interleave = [0, 2, 4, 6, 1, 3, 5, 7]
+    weight_interleaved = (
+        weight_int4_orig.reshape(-1, 8)[:, awq_interleave].reshape(K, N).contiguous()
+    )
+    packed_qweight = pack_cols(weight_interleaved, 4, K, N)
+
+    zeros_interleaved = (
+        zeros_int4_orig.reshape(-1, 8)[:, awq_interleave]
+        .reshape(num_groups, N)
+        .contiguous()
+    )
+    packed_qzeros = pack_cols(zeros_interleaved, 4, num_groups, N)
+
+    return (
+        packed_qweight,
+        packed_qzeros,
+        scales,
+        float_ref,
+        weight_int4_orig,
+        zeros_int4_orig,
+    )
+
+
+class TestConvertWeightPackedScaleZp:
+    """Tests for convert_weight_packed_scale_zp weightpacking."""
+
+    @requires_cpu_w4a8_int8
+    @pytest.mark.parametrize(
+        "K,N,group_size",
+        [
+            (128, 128, 128),
+            (256, 256, 128),
+            (512, 256, 64),
+        ],
+    )
+    def test_packing_output_shapes(self, K, N, group_size):
+        """Packed outputs should have expected shapes."""
+        (packed_qweight, packed_qzeros, scales, _, _, _) = make_awq_checkpoint_data(
+            K, N, group_size
+        )
+
+        blocked_w, blocked_zp, blocked_s = torch.ops._C.convert_weight_packed_scale_zp(
+            packed_qweight, packed_qzeros, scales
+        )
+
+        block_n = 32
+        Nc = N // block_n
+
+        assert blocked_w.dim() >= 2, (
+            f"blocked_w should have >= 2 dims, got {blocked_w.dim()}"
+        )
+        assert blocked_s.size(0) == Nc, (
+            f"Expected Nc={Nc} scale blocks, got {blocked_s.size(0)}"
+        )
+        assert blocked_zp.size(0) == Nc, (
+            f"Expected Nc={Nc} qzeros blocks, got {blocked_zp.size(0)}"
+        )
+
+        print(
+            f"  [PASS] packing shapes K={K}, N={N}, gs={group_size}: "
+            f"blocked_w={list(blocked_w.shape)}, "
+            f"blocked_s={list(blocked_s.shape)}, blocked_zp={list(blocked_zp.shape)}"
+        )
+
+
+class TestInt4ScaledMmCpu:
+    """Tests for int4_scaled_mm_cpu GEMM kernel."""
+
+    @requires_cpu_w4a8_int8
+    @pytest.mark.parametrize(
+        "M,K,N,group_size",
+        [
+            (1, 128, 128, 128),
+            (4, 256, 256, 128),
+            (16, 512, 256, 64),
+            (32, 256, 512, 128),
+            (64, 512, 512, 128),
+        ],
+    )
+    def test_gemm_vs_float_reference(self, M, K, N, group_size):
+        """INT4 W4A8 GEMM should approximate float matmul."""
+        (packed_qweight, packed_qzeros, scales, float_ref, _, _) = (
+            make_awq_checkpoint_data(K, N, group_size)
+        )
+
+        blocked_w, blocked_zp, blocked_s = torch.ops._C.convert_weight_packed_scale_zp(
+            packed_qweight, packed_qzeros, scales
+        )
+
+        x = torch.randn(M, K, dtype=torch.bfloat16)
+        out = torch.ops._C.int4_scaled_mm_cpu(x, blocked_w, blocked_zp, blocked_s, None)
+
+        ref_out = torch.mm(x.float(), float_ref)
+
+        abs_diff = (out.float() - ref_out).abs()
+        mean_abs = abs_diff.mean().item()
+        pct95 = torch.quantile(abs_diff, 0.95).item()
+        ref_mag = ref_out.abs().mean().item() + 1e-6
+        mean_rel = mean_abs / ref_mag
+
+        assert mean_rel < 0.05, (
+            f"Mean relative error {mean_rel:.4f} exceeds 5% threshold"
+        )
+        assert pct95 < ref_mag * 0.15, (
+            f"95th-pctile abs_diff {pct95:.4f} exceeds 15% of ref magnitude"
+        )
+        print(f"  [PASS] INT4 GEMM correct: M={M}, K={K}, N={N}")
+
+    @requires_cpu_w4a8_int8
+    @pytest.mark.parametrize("M", [1, 8, 32])
+    def test_gemm_with_bias(self, M):
+        """INT4 W4A8 GEMM with bias should match reference."""
+        K, N, group_size = 256, 128, 128
+        (packed_qweight, packed_qzeros, scales, float_ref, _, _) = (
+            make_awq_checkpoint_data(K, N, group_size)
+        )
+
+        blocked_w, blocked_zp, blocked_s = torch.ops._C.convert_weight_packed_scale_zp(
+            packed_qweight, packed_qzeros, scales
+        )
+
+        bias = torch.randn(N, dtype=torch.float32)
+        x = torch.randn(M, K, dtype=torch.bfloat16)
+
+        out = torch.ops._C.int4_scaled_mm_cpu(x, blocked_w, blocked_zp, blocked_s, bias)
+
+        ref_out = torch.mm(x.float(), float_ref) + bias
+        abs_diff = (out.float() - ref_out).abs()
+        mean_abs = abs_diff.mean().item()
+        ref_mag = ref_out.abs().mean().item() + 1e-6
+        mean_rel = mean_abs / ref_mag
+        assert mean_rel < 0.05, (
+            f"Mean relative error {mean_rel:.4f} with bias exceeds 5%"
+        )
+        print(f"  [PASS] INT4 GEMM with bias: M={M}")
+
+    @requires_cpu_w4a8_int8
+    def test_gemm_3d_input(self):
+        """apply() reshapes 3D input [B, S, K] -> [B*S, K] -> back to 3D."""
+        K, N, group_size = 256, 128, 128
+        (packed_qweight, packed_qzeros, scales, float_ref, _, _) = (
+            make_awq_checkpoint_data(K, N, group_size)
+        )
+
+        blocked_w, blocked_zp, blocked_s = torch.ops._C.convert_weight_packed_scale_zp(
+            packed_qweight, packed_qzeros, scales
+        )
+
+        B, S = 2, 8
+        x_3d = torch.randn(B, S, K, dtype=torch.bfloat16)
+        x_2d = x_3d.reshape(-1, K)
+
+        out_2d = torch.ops._C.int4_scaled_mm_cpu(
+            x_2d, blocked_w, blocked_zp, blocked_s, None
+        )
+        out_3d = out_2d.reshape(B, S, N)
+
+        ref_out = torch.mm(x_2d.float(), float_ref).reshape(B, S, N)
+
+        assert out_3d.shape == (B, S, N)
+        abs_diff = (out_3d.float() - ref_out).abs()
+        mean_abs = abs_diff.mean().item()
+        ref_mag = ref_out.abs().mean().item() + 1e-6
+        mean_rel = mean_abs / ref_mag
+
+        assert mean_rel < 0.05, f"Mean relative error {mean_rel:.4f} for 3D exceeds 5%"
+        print(f"  [PASS] 3D input [{B},{S},{K}] -> output [{B},{S},{N}]")
+
+    @requires_cpu_w4a8_int8
+    def test_gemm_fp16_input(self):
+        """INT4 GEMM should also work with fp16 input."""
+        K, N, group_size, M = 256, 256, 128, 8
+        (packed_qweight, packed_qzeros, scales, float_ref, _, _) = (
+            make_awq_checkpoint_data(K, N, group_size)
+        )
+
+        blocked_w, blocked_zp, blocked_s = torch.ops._C.convert_weight_packed_scale_zp(
+            packed_qweight, packed_qzeros, scales
+        )
+
+        x = torch.randn(M, K, dtype=torch.float16)
+        out = torch.ops._C.int4_scaled_mm_cpu(x, blocked_w, blocked_zp, blocked_s, None)
+
+        ref_out = torch.mm(x.float(), float_ref)
+        abs_diff = (out.float() - ref_out).abs()
+        ref_mag = ref_out.abs().mean().item() + 1e-6
+        mean_rel = abs_diff.mean().item() / ref_mag
+
+        assert mean_rel < 0.05, (
+            f"Mean relative error {mean_rel:.4f} for fp16 exceeds 5%"
+        )
+        print(f"  [PASS] fp16 input M={M}, K={K}, N={N}")
+
+
+class TestCreateWeightsUnchanged:
+    """Create_weights should still produce correct int4 placeholder shapes."""
+
+    @pytest.mark.parametrize(
+        "K,N,group_size",
+        [
+            (128, 128, 128),
+            (256, 256, 128),
+            (512, 256, 64),
+        ],
+    )
+    def test_int4_placeholder_shapes(self, K, N, group_size):
+        """Verify qweight, qzeros, scales shapes."""
+        pack_factor = 8
+        num_groups = K // group_size
+
+        qweight = torch.empty(K, N // pack_factor, dtype=torch.int32)
+        qzeros = torch.empty(num_groups, N // pack_factor, dtype=torch.int32)
+        scales = torch.empty(num_groups, N, dtype=torch.bfloat16)
+
+        assert qweight.shape == (K, N // pack_factor)
+        assert qzeros.shape == (num_groups, N // pack_factor)
+        assert scales.shape == (num_groups, N)
+        print(f"  [PASS] create_weights shapes: K={K}, N={N}, gs={group_size}")

vllm/_custom_ops.py

@@ -2967,6 +2967,38 @@ if hasattr(torch.ops._C, "int8_scaled_mm_with_quant"):
         return torch.empty((M, N), dtype=out_dtype)
 
 
+if hasattr(torch.ops._C, "convert_weight_packed_scale_zp"):
+
+    @register_fake("_C::convert_weight_packed_scale_zp")
+    def convert_weight_packed_scale_zp_fake(
+        qweight: torch.Tensor,
+        qzeros: torch.Tensor,
+        scales: torch.Tensor,
+    ) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
+        return (
+            torch.empty_like(qweight),
+            torch.empty_like(qzeros),
+            torch.empty_like(scales),
+        )
+
+
+if hasattr(torch.ops._C, "int4_scaled_mm_cpu"):
+
+    @register_fake("_C::int4_scaled_mm_cpu")
+    def int4_scaled_mm_cpu_fake(
+        x: torch.Tensor,
+        w: torch.Tensor,
+        w_zeros: torch.Tensor,
+        w_scales: torch.Tensor,
+        bias: torch.Tensor | None,
+    ) -> torch.Tensor:
+        N = w_scales.size(0) * w_scales.size(-1)
+        return torch.empty((x.size(0), N), dtype=x.dtype, device=x.device)
+
+
+_supports_cpu_w4a8_int8 = bool(hasattr(torch.ops._C, "convert_weight_packed_scale_zp"))
+
+
 class CPUDNNLGEMMHandler:
     def __init__(self) -> None:
         self.handler_tensor: torch.Tensor | None = None

vllm/envs.py

@@ -52,6 +52,7 @@ if TYPE_CHECKING:
     VLLM_CPU_NUM_OF_RESERVED_CPU: int | None = None
     VLLM_CPU_SGL_KERNEL: bool = False
     VLLM_ZENTORCH_WEIGHT_PREPACK: bool = True
+    VLLM_CPU_INT4_W4A8: bool = True
     VLLM_XLA_CACHE_PATH: str = os.path.join(VLLM_CACHE_ROOT, "xla_cache")
     VLLM_XLA_CHECK_RECOMPILATION: bool = False
     VLLM_USE_RAY_COMPILED_DAG_CHANNEL_TYPE: Literal["auto", "nccl", "shm"] = "auto"
@@ -728,6 +729,8 @@ environment_variables: dict[str, Callable[[], Any]] = {
     "VLLM_ZENTORCH_WEIGHT_PREPACK": lambda: bool(
         int(os.getenv("VLLM_ZENTORCH_WEIGHT_PREPACK", "1"))
     ),
+    # (CPU backend only) whether to use SGLang INT4 W4A8 kernels for AWQ.
+    "VLLM_CPU_INT4_W4A8": lambda: bool(int(os.getenv("VLLM_CPU_INT4_W4A8", "1"))),
     # If the env var is set, Ray Compiled Graph uses the specified
     # channel type to communicate between workers belonging to
     # different pipeline-parallel stages.

vllm/model_executor/layers/quantization/cpu_wna16.py

@@ -7,9 +7,8 @@ import torch
 from safetensors.torch import _TYPES as _SAFETENSORS_TO_TORCH_DTYPE
 from transformers import PretrainedConfig
 
-from vllm._custom_ops import (
+import vllm.envs as envs
-    cpu_gemm_wna16,
+from vllm import _custom_ops as ops
-)
 from vllm.logger import init_logger
 from vllm.model_executor.layers.linear import (
     LinearBase,
@@ -230,7 +229,14 @@ class CPUAWQLinearMethod(LinearMethodBase):
         layer.register_parameter("scales", scales)
 
     def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
-        torch.set_printoptions(profile="full", linewidth=5000, sci_mode=False)
+        layer.use_w4a8 = envs.VLLM_CPU_INT4_W4A8 and torch.cpu._is_amx_tile_supported()
+        if layer.use_w4a8:
+            self._process_weights_sglang_int4(layer)
+        else:
+            self._process_weights_woq(layer)
+
+    def _process_weights_woq(self, layer: torch.nn.Module) -> None:
+        """Original WOQ int4 repack path."""
         packed_weight = layer.qweight.data
         packed_zeros = layer.qzeros.data
         group_num = packed_zeros.size(0)
@@ -266,8 +272,6 @@ class CPUAWQLinearMethod(LinearMethodBase):
         )
 
         zeros = pack_cols(zeros, bits, group_num, output_size).contiguous()
-        # make 16 output channel as a block and transpose to
-        # the make the block contiguous
         weight = pack_cols(weight, bits, input_size, output_size)
         weight = (
             weight.view(input_size, -1, 16 // pack_factor)
@@ -278,13 +282,40 @@ class CPUAWQLinearMethod(LinearMethodBase):
         layer.qweight.data = weight
         layer.qzeros.data = zeros
 
+    def _process_weights_sglang_int4(self, layer: torch.nn.Module) -> None:
+        """SGLang INT4 W4A8 path: pack int4 weights with VNNI reordering."""
+        packed_weight = layer.qweight.data
+        packed_zeros = layer.qzeros.data
+        scales = layer.scales.data
+        blocked_w, blocked_zp, blocked_s = torch.ops._C.convert_weight_packed_scale_zp(
+            packed_weight, packed_zeros, scales
+        )
+
+        layer.packed_weight = blocked_w
+        layer.packed_qzeros = blocked_zp
+        layer.packed_scales = blocked_s
+        layer.qweight = None
+        layer.qzeros = None
+        layer.scales = None
+
     def apply(
         self,
         layer: torch.nn.Module,
         x: torch.Tensor,
         bias: torch.Tensor | None = None,
     ) -> torch.Tensor:
-        x = cpu_gemm_wna16(
+        if layer.use_w4a8:
+            return self._apply_sglang_int4(layer, x, bias)
+        return self._apply_woq(layer, x, bias)
+
+    def _apply_woq(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: torch.Tensor | None = None,
+    ) -> torch.Tensor:
+        """Original WOQ int4 GEMM path."""
+        x = ops.cpu_gemm_wna16(
             input=x,
             q_weight=layer.qweight,
             scales=layer.scales,
@@ -296,6 +327,26 @@ class CPUAWQLinearMethod(LinearMethodBase):
         )
         return x
 
+    def _apply_sglang_int4(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: torch.Tensor | None = None,
+    ) -> torch.Tensor:
+        """SGLang INT4 W4A8 GEMM path."""
+        x_shape = x.shape
+        x_2d = x.reshape(-1, x_shape[-1]) if len(x_shape) > 2 else x
+
+        out = torch.ops._C.int4_scaled_mm_cpu(
+            x_2d,
+            layer.packed_weight,
+            layer.packed_qzeros,
+            layer.packed_scales,
+            bias,
+        )
+        out = out.reshape(x_shape[:-1] + (out.size(-1),)) if len(x_shape) > 2 else out
+        return out
+
 
 def _get_isa_hint(dtype: torch.dtype) -> str:
     supports_amx = torch.cpu._is_amx_tile_supported()