/******************************************************************************
 * Copyright (c) 2023, Tri Dao.
 ******************************************************************************/

#pragma once

#include <assert.h>
#include <cuda_fp16.h>
#include <stdint.h>
#include <stdlib.h>

#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 800
#include <cuda_bf16.h>
#endif

#include <cutlass/array.h>
#include <cutlass/cutlass.h>
#include <cutlass/numeric_conversion.h>
#include <cutlass/numeric_types.h>

#include <cute/tensor.hpp>

using namespace cute;

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

namespace flash {

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

template <typename T>
__forceinline__ __device__ uint32_t relu2(const uint32_t x);

template <>
__forceinline__ __device__ uint32_t relu2<cutlass::half_t>(const uint32_t x) {
  uint32_t res;
  const uint32_t zero = 0u;
#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 800
  asm volatile("max.f16x2 %0, %1, %2;\n" : "=r"(res) : "r"(x), "r"(zero));
#else
  asm volatile(
      "{\n"
      "\t .reg .f16x2 sela;\n"
      "\t set.gtu.u32.f16x2 sela, %1, %2;\n"
      "\t and.b32 %0, sela, %1;\n"
      "}\n"
      : "=r"(res)
      : "r"(x), "r"(zero));
#endif
  return res;
}

#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 800
template <>
__forceinline__ __device__ uint32_t relu2<cutlass::bfloat16_t>(const uint32_t x) {
  uint32_t res;
  const uint32_t zero = 0u;
  asm volatile("max.bf16x2 %0, %1, %2;\n" : "=r"(res) : "r"(x), "r"(zero));
  return res;
}
#endif

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

#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 800

template <typename T>
__forceinline__ __device__ uint32_t convert_relu2(const float2 x);

template <>
__forceinline__ __device__ uint32_t convert_relu2<cutlass::half_t>(const float2 x) {
  uint32_t res;
  const uint32_t a = reinterpret_cast<const uint32_t&>(x.x);
  const uint32_t b = reinterpret_cast<const uint32_t&>(x.y);
  asm volatile("cvt.rn.relu.f16x2.f32 %0, %1, %2;\n" : "=r"(res) : "r"(b), "r"(a));
  return res;
}

template <>
__forceinline__ __device__ uint32_t convert_relu2<cutlass::bfloat16_t>(const float2 x) {
  uint32_t res;
  const uint32_t a = reinterpret_cast<const uint32_t&>(x.x);
  const uint32_t b = reinterpret_cast<const uint32_t&>(x.y);
  asm volatile("cvt.rn.relu.bf16x2.f32 %0, %1, %2;\n" : "=r"(res) : "r"(b), "r"(a));
  return res;
}

#endif

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

template <typename T>
struct MaxOp {
  __device__ __forceinline__ T operator()(T const& x, T const& y) {
    return x > y ? x : y;
  }
};

template <>
struct MaxOp<float> {
  // This is slightly faster
  __device__ __forceinline__ float operator()(float const& x, float const& y) {
    return max(x, y);
  }
};

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

template <typename T>
struct SumOp {
  __device__ __forceinline__ T operator()(T const& x, T const& y) {
    return x + y;
  }
};

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

template <int THREADS>
struct Allreduce {
  static_assert(THREADS == 32 || THREADS == 16 || THREADS == 8 || THREADS == 4);
  template <typename T, typename Operator>
  static __device__ __forceinline__ T run(T x, Operator& op) {
    constexpr int OFFSET = THREADS / 2;
    x = op(x, __shfl_xor_sync(uint32_t(-1), x, OFFSET));
    return Allreduce<OFFSET>::run(x, op);
  }
};

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

template <>
struct Allreduce<2> {
  template <typename T, typename Operator>
  static __device__ __forceinline__ T run(T x, Operator& op) {
    x = op(x, __shfl_xor_sync(uint32_t(-1), x, 1));
    return x;
  }
};

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

template <
    bool A_in_regs = false,
    bool B_in_regs = false,
    typename Tensor0,
    typename Tensor1,
    typename Tensor2,
    typename Tensor3,
    typename Tensor4,
    typename TiledMma,
    typename TiledCopyA,
    typename TiledCopyB,
    typename ThrCopyA,
    typename ThrCopyB>
__forceinline__ __device__ void gemm(
    Tensor0& acc,
    Tensor1& tCrA,
    Tensor2& tCrB,
    Tensor3 const& tCsA,
    Tensor4 const& tCsB,
    TiledMma tiled_mma,
    TiledCopyA smem_tiled_copy_A,
    TiledCopyB smem_tiled_copy_B,
    ThrCopyA smem_thr_copy_A,
    ThrCopyB smem_thr_copy_B) {
  CUTE_STATIC_ASSERT_V(size<1>(tCrA) == size<1>(acc));   // MMA_M
  CUTE_STATIC_ASSERT_V(size<1>(tCrB) == size<2>(acc));   // MMA_N
  CUTE_STATIC_ASSERT_V(size<2>(tCrA) == size<2>(tCrB));  // MMA_K
  Tensor tCrA_copy_view = smem_thr_copy_A.retile_D(tCrA);
  CUTE_STATIC_ASSERT_V(size<1>(tCsA) == size<1>(tCrA_copy_view));  // M
  Tensor tCrB_copy_view = smem_thr_copy_B.retile_D(tCrB);
  CUTE_STATIC_ASSERT_V(size<1>(tCsB) == size<1>(tCrB_copy_view));  // N
  if (!A_in_regs) {
    cute::copy(smem_tiled_copy_A, tCsA(_, _, _0{}), tCrA_copy_view(_, _, _0{}));
  }
  if (!B_in_regs) {
    cute::copy(smem_tiled_copy_B, tCsB(_, _, _0{}), tCrB_copy_view(_, _, _0{}));
  }
#pragma unroll
  for (int i = 0; i < size<2>(tCrA); ++i) {
    if (i < size<2>(tCrA) - 1) {
      if (!A_in_regs) {
        cute::copy(smem_tiled_copy_A, tCsA(_, _, i + 1), tCrA_copy_view(_, _, i + 1));
      }
      if (!B_in_regs) {
        cute::copy(smem_tiled_copy_B, tCsB(_, _, i + 1), tCrB_copy_view(_, _, i + 1));
      }
    }
    cute::gemm(tiled_mma, tCrA(_, _, i), tCrB(_, _, i), acc);
  }
}

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

template <
    typename Tensor0,
    typename Tensor1,
    typename Tensor2,
    typename Tensor3,
    typename TiledMma,
    typename TiledCopy,
    typename ThrCopy>
__forceinline__ __device__ void gemm_rs(
    Tensor0& acc,
    Tensor1& tCrA,
    Tensor2& tCrB,
    Tensor3 const& tCsB,
    TiledMma tiled_mma,
    TiledCopy smem_tiled_copy_B,
    ThrCopy smem_thr_copy_B) {
  CUTE_STATIC_ASSERT_V(size<1>(tCrA) == size<1>(acc));   // MMA_M
  CUTE_STATIC_ASSERT_V(size<1>(tCrB) == size<2>(acc));   // MMA_N
  CUTE_STATIC_ASSERT_V(size<2>(tCrA) == size<2>(tCrB));  // MMA_K
  Tensor tCrB_copy_view = smem_thr_copy_B.retile_D(tCrB);
  CUTE_STATIC_ASSERT_V(size<1>(tCsB) == size<1>(tCrB_copy_view));  // N
  cute::copy(smem_tiled_copy_B, tCsB(_, _, _0{}), tCrB_copy_view(_, _, _0{}));
#pragma unroll
  for (int i = 0; i < size<2>(tCrA); ++i) {
    if (i < size<2>(tCrA) - 1) {
      cute::copy(smem_tiled_copy_B, tCsB(_, _, i + 1), tCrB_copy_view(_, _, i + 1));
    }
    cute::gemm(tiled_mma, tCrA(_, _, i), tCrB(_, _, i), acc);
  }
}

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

// Convert acc_layout from (MMA=4, MMA_M, MMA_N) to (nrow=(2, MMA_M), ncol=(2, MMA_N))
template <typename Layout>
__forceinline__ __device__ auto convert_layout_acc_rowcol(Layout acc_layout) {
  static_assert(decltype(size<0>(acc_layout))::value == 4);
  static_assert(decltype(rank(acc_layout))::value == 3);
  auto l = logical_divide(acc_layout, Shape<_2>{});  // ((2, 2), MMA_M, MMA_N)
  return make_layout(make_layout(get<0, 1>(l), get<1>(l)), make_layout(get<0, 0>(l), get<2>(l)));
};

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

// Convert acc_layout from (MMA=4, MMA_M, MMA_N) to ((4, 2), MMA_M, MMA_N / 2)
// if using m16n8k16, or to (4, MMA_M, MMA_N) if using m16n8k8.
template <typename MMA_traits, typename Layout>
__forceinline__ __device__ auto convert_layout_acc_Aregs(Layout acc_layout) {
  using X = Underscore;
  static_assert(decltype(size<0>(acc_layout))::value == 4);
  static_assert(decltype(rank(acc_layout))::value == 3);
  constexpr int mma_shape_K = get<2>(typename MMA_traits::Shape_MNK{});
  static_assert(mma_shape_K == 8 || mma_shape_K == 16);
  if constexpr (mma_shape_K == 8) {
    return acc_layout;
  } else {
    auto l = logical_divide(acc_layout, Shape<X, X, _2>{});  // (4, MMA_M, (2, MMA_N / 2)))
    return make_layout(make_layout(get<0>(l), get<2, 0>(l)), get<1>(l), get<2, 1>(l));
  }
};

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

// Convert acc_layout from (MMA=4, MMA_M, MMA_N) to ((4, 2), MMA_M, MMA_N / 2)
template <typename Layout>
__forceinline__ __device__ auto convert_layout_acc_dropout(Layout acc_layout) {
  using X = Underscore;
  static_assert(decltype(size<0>(acc_layout))::value == 4);
  static_assert(decltype(rank(acc_layout))::value == 3);
  auto l = logical_divide(acc_layout, Shape<X, X, _2>{});  // (4, MMA_M, (2, MMA_N / 2)))
  return make_layout(make_layout(get<0>(l), get<2, 0>(l)), get<1>(l), get<2, 1>(l));
};

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

template <typename To_type, typename Engine, typename Layout>
__forceinline__ __device__ auto convert_type(Tensor<Engine, Layout> const& tensor) {
  using From_type = typename Engine::value_type;
  constexpr int numel = decltype(size(tensor))::value;
  cutlass::NumericArrayConverter<To_type, From_type, numel> convert_op;
  // HACK: this requires tensor to be "contiguous"
  auto frag = convert_op(*reinterpret_cast<const cutlass::Array<From_type, numel>*>(tensor.data()));
  return make_tensor(make_rmem_ptr<To_type>(&frag), tensor.layout());
}

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

template <typename Engine, typename Layout>
__forceinline__ __device__ void relu_(Tensor<Engine, Layout>& tensor) {
  constexpr int numel = decltype(size(tensor))::value;
  static_assert(numel % 2 == 0);
  using value_t = typename Engine::value_type;
  // HACK: this requires tensor to be "contiguous"
  Tensor tensor_uint32 = recast<uint32_t>(tensor);
#pragma unroll
  for (int i = 0; i < size(tensor_uint32); ++i) {
    tensor_uint32(i) = relu2<value_t>(tensor_uint32(i));
  }
}

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

// On SM80 and above, we can fuse fp32 -> fp16/bf16 conversion and relu into 1 instruction
template <typename To_type, typename Engine, typename Layout>
__forceinline__ __device__ auto convert_type_relu(Tensor<Engine, Layout> const& tensor) {
  using From_type = typename Engine::value_type;
  static_assert(std::is_same_v<To_type, cutlass::half_t> || std::is_same_v<To_type, cutlass::bfloat16_t>);
  static_assert(std::is_same_v<float, From_type>);
  constexpr int numel = decltype(size(tensor))::value;
  static_assert(numel % 2 == 0);
#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 800
  // HACK: this requires tensor to be "contiguous"
  Tensor tensor_float2 = recast<float2>(tensor);
  Tensor out_uint32 = make_tensor<uint32_t>(tensor_float2.layout());
#pragma unroll
  for (int i = 0; i < size(out_uint32); ++i) {
    out_uint32(i) = convert_relu2<To_type>(tensor_float2(i));
  }
  Tensor out = make_tensor(make_rmem_ptr<To_type>(out_uint32.data()), tensor.layout());
#else
  Tensor out = flash::convert_type<To_type>(tensor);
  flash::relu_(out);
#endif
  return out;
}

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

// Blocks until all but N previous cp.async.commit_group operations have committed.
// This differs from cute::cp_async_wait in that when N = 0 we don't call cp.async.wait_all
// (which is equivalent to commit_group then wait_group 0).
// Instead we just call cp.async.wait_group 0, which is slightly faster.
// https://github.com/NVIDIA/cutlass/blob/master/include/cute/arch/copy_sm80.hpp#L113
template <int N>
CUTE_HOST_DEVICE void cp_async_wait() {
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
  asm volatile("cp.async.wait_group %0;\n" ::"n"(N));
#endif
}

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

template <
    bool Is_even_MN = true,
    bool Is_even_K = true,
    bool Clear_OOB_MN = false,
    bool Clear_OOB_K = true,
    typename TiledCopy,
    typename Engine0,
    typename Layout0,
    typename Engine1,
    typename Layout1,
    typename Engine2,
    typename Layout2,
    typename Engine3,
    typename Layout3>
__forceinline__ __device__ void copy(
    TiledCopy tiled_copy,
    Tensor<Engine0, Layout0> const& S,
    Tensor<Engine1, Layout1>& D,
    Tensor<Engine2, Layout2> const& identity_MN,
    Tensor<Engine3, Layout3> const& predicate_K,
    const int max_MN = 0) {
  CUTE_STATIC_ASSERT_V(rank(S) == Int<3>{});
  CUTE_STATIC_ASSERT_V(rank(D) == Int<3>{});
  CUTE_STATIC_ASSERT_V(size<0>(S) == size<0>(D));  // MMA
  CUTE_STATIC_ASSERT_V(size<1>(S) == size<1>(D));  // MMA_M
  CUTE_STATIC_ASSERT_V(size<2>(S) == size<2>(D));  // MMA_K
  // There's no case where !Clear_OOB_K && Clear_OOB_MN
  static_assert(!(Clear_OOB_MN && !Clear_OOB_K));
#pragma unroll
  for (int m = 0; m < size<1>(S); ++m) {
    if (Is_even_MN || get<0>(identity_MN(0, m, 0)) < max_MN) {
#pragma unroll
      for (int k = 0; k < size<2>(S); ++k) {
        if (Is_even_K || predicate_K(k)) {
          cute::copy(tiled_copy, S(_, m, k), D(_, m, k));
        } else if (Clear_OOB_K) {
          cute::clear(D(_, m, k));
        }
      }
    } else if (Clear_OOB_MN) {
      cute::clear(D(_, m, _));
    }
  }
  // TD [2023-04-13]: Strange that the code below can cause race condition.
  // I think it's because the copies are under an if statement.
  // if (Is_even_K) {
  //     #pragma unroll
  //     for (int m = 0; m < size<1>(S); ++m) {
  //         if (Is_even_MN || get<0>(identity_MN(0, m, 0)) < max_MN) {
  //             copy(tiled_copy, S(_, m, _), D(_, m, _));
  //         } else if (Clear_OOB_MN) {
  //             clear(D(_, m, _));
  //         }
  //     }
  // } else {  // It's slightly faster in this case if iterate over K first
  //     #pragma unroll
  //     for (int k = 0; k < size<2>(S); ++k) {
  //         if (predicate_K(k)) {
  //             #pragma unroll
  //             for (int m = 0; m < size<1>(S); ++m) {
  //                 if (Is_even_MN || get<0>(identity_MN(0, m, 0)) < max_MN) {
  //                     copy(tiled_copy, S(_, m, k), D(_, m, k));
  //                 } else if (Clear_OOB_MN) {
  //                     clear(D(_, m, k));
  //                 }
  //             }
  //         } else if (Clear_OOB_K) {  // There's no case where !Clear_OOB_K && Clear_OOB_MN
  //             if (Clear_OOB_MN || Is_even_MN) {
  //                 clear(D(_, _, k));
  //             } else {
  //                 #pragma unroll
  //                 for (int m = 0; m < size<1>(S); ++m) {
  //                     if (!(Is_even_MN || get<0>(identity_MN(0, m, 0)) < max_MN)) {
  //                         clear(D(_, m, k));
  //                     }
  //                 }
  //             }
  //         }
  //     }
  // }
}

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

template <
    bool Is_even_K = true,
    typename Engine0,
    typename Layout0,
    typename Engine1,
    typename Layout1,
    typename Engine2,
    typename Layout2,
    typename Engine3,
    typename Layout3>
__forceinline__ __device__ void copy_w_min_idx(
    Tensor<Engine0, Layout0> const& S,
    Tensor<Engine1, Layout1>& D,
    Tensor<Engine2, Layout2> const& identity_MN,
    Tensor<Engine3, Layout3> const& predicate_K,
    const int max_MN = 0,
    const int min_MN = 0) {
  CUTE_STATIC_ASSERT_V(rank(S) == Int<3>{});
  CUTE_STATIC_ASSERT_V(rank(D) == Int<3>{});
  CUTE_STATIC_ASSERT_V(size<0>(S) == size<0>(D));  // MMA
  CUTE_STATIC_ASSERT_V(size<1>(S) == size<1>(D));  // MMA_M
  CUTE_STATIC_ASSERT_V(size<2>(S) == size<2>(D));  // MMA_K
// if (threadIdx.x == 0 && blockIdx.z == 0) { printf("blockIdx.y = %d, max_MN = %d, min_MN = %d\n", blockIdx.y, max_MN,
// min_MN); }
#pragma unroll
  for (int m = 0; m < size<1>(S); ++m) {
    // if (threadIdx.x == 0 && blockIdx.z == 0) { printf("blockIdx.y = %d, m = %d\n", blockIdx.y, get<0>(identity_MN(0,
    // m, 0))); }
    if (get<0>(identity_MN(0, m, 0)) >= min_MN && get<0>(identity_MN(0, m, 0)) < max_MN) {
// if (threadIdx.x == 0 && blockIdx.z == 0) { printf("Inner loop, blockIdx.y = %d, m = %d\n", blockIdx.y,
// get<0>(identity_MN(0, m, 0))); }
#pragma unroll
      for (int k = 0; k < size<2>(S); ++k) {
        if (Is_even_K || predicate_K(k)) {
          cute::copy(S(_, m, k), D(_, m, k));
        }
      }
    }
  }
}

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

template <typename Engine, typename Layout>
__forceinline__ __device__ void apply_softcap(Tensor<Engine, Layout>& tensor, const float softcap) {
#pragma unroll
  for (int i = 0; i < size(tensor); ++i) {
    tensor(i) = cutlass::fast_tanh(tensor(i) * softcap);
  }
}

template <typename Engine0, typename Layout0, typename Engine1, typename Layout1>
__forceinline__ __device__ void
calculate_dtanh(Tensor<Engine0, Layout0>& src_tensor, Tensor<Engine1, Layout1>& dst_tensor, const float softcap) {
#pragma unroll
  for (int i = 0; i < size(src_tensor); ++i) {
    dst_tensor(i) = (1.f - (src_tensor(i) * src_tensor(i))) * softcap;
  }
}

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

}  // namespace flash
