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#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/gemm/dispatch_policy.hpp"

#include "cute/algorithm/functional.hpp"
#include "cute/atom/mma_atom.hpp"
#include "cute/algorithm/gemm.hpp"
#include "cute/tensor_predicate.hpp"
#include "cute/numeric/arithmetic_tuple.hpp"


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

namespace cutlass::gemm::collective {
using namespace cute;

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

template <
  int Stages,
  class TileShape_,
  class ElementA_,
  class StrideA_,
  class ElementB_,
  class StrideB_,
  class TiledMma_,
  class GmemTiledCopyA_,
  class SmemLayoutAtomA_,
  class SmemCopyAtomA_,
  class TransformA_,
  class GmemTiledCopyB_,
  class SmemLayoutAtomB_,
  class SmemCopyAtomB_,
  class TransformB_>
struct CollectiveMma<
    MainloopSm80CpAsyncUnpredicated<Stages>,
    TileShape_,
    ElementA_,
    StrideA_,
    ElementB_,
    StrideB_,
    TiledMma_,
    GmemTiledCopyA_,
    SmemLayoutAtomA_,
    SmemCopyAtomA_,
    TransformA_,
    GmemTiledCopyB_,
    SmemLayoutAtomB_,
    SmemCopyAtomB_,
    TransformB_>
{
  //
  // Type Aliases
  //
  using DispatchPolicy = MainloopSm80CpAsyncUnpredicated<Stages>;
  using TileShape = TileShape_;
  using ElementA = ElementA_;
  using StrideA = StrideA_;
  using ElementB = ElementB_;
  using StrideB = StrideB_;
  using TiledMma = TiledMma_;
  using ElementAccumulator = typename TiledMma::ValTypeC;
  using GmemTiledCopyA = GmemTiledCopyA_;
  using GmemTiledCopyB = GmemTiledCopyB_;
  using SmemLayoutAtomA = SmemLayoutAtomA_;
  using SmemLayoutAtomB = SmemLayoutAtomB_;
  using SmemCopyAtomA = SmemCopyAtomA_;
  using SmemCopyAtomB = SmemCopyAtomB_;
  using TransformA = TransformA_;
  using TransformB = TransformB_;
  using ArchTag = typename DispatchPolicy::ArchTag;

  static_assert(rank(SmemLayoutAtomA{}) == 2, "SmemLayoutAtom must be rank 2 (M/N, K)");
  static_assert((size<0>(TileShape{}) % size<0>(SmemLayoutAtomA{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");
  static_assert((size<2>(TileShape{}) % size<1>(SmemLayoutAtomA{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");

  static_assert(rank(SmemLayoutAtomB{}) == 2, "SmemLayoutAtom must be rank 2 (M/N, K)");
  static_assert((size<1>(TileShape{}) % size<0>(SmemLayoutAtomB{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");
  static_assert((size<2>(TileShape{}) % size<1>(SmemLayoutAtomB{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");

  using SmemLayoutA = decltype(tile_to_shape(
      SmemLayoutAtomA{},
      make_shape(shape<0>(TileShape{}), shape<2>(TileShape{}), Int<DispatchPolicy::Stages>{})));
  using SmemLayoutB = decltype(tile_to_shape(
      SmemLayoutAtomB{},
      make_shape(shape<1>(TileShape{}), shape<2>(TileShape{}), Int<DispatchPolicy::Stages>{})));

  static_assert(DispatchPolicy::Stages >= 2, "CpAsync mainloop must have at least 2 stages in the pipeline.");

  struct SharedStorage
  {
    cute::array_aligned<ElementA, cute::cosize_v<SmemLayoutA>> smem_a;
    cute::array_aligned<ElementB, cute::cosize_v<SmemLayoutB>> smem_b;
  };

  struct Params {
    ElementA const* ptr_A;
    StrideA dA;
    ElementB const* ptr_B;
    StrideB dB;
  };

  //
  // Methods
  //

  CollectiveMma() = default;

  template <class Args>
  static constexpr Params
  to_underlying_arguments(Args const& args, void* workspace) {
    (void) workspace;
    return {args.ptr_A, args.dA, args.ptr_B, args.dB};
  }

  /// Perform a collective-scoped matrix multiply-accumulate
  template <
    class FrgTensorD,
    class TensorA,
    class TensorB,
    class FrgTensorC,
    class KTileIterator,
    class ResidueMNK
  >
  CUTLASS_DEVICE void
  operator() (
      FrgTensorD &accum,
      TensorA gA,
      TensorB gB,
      FrgTensorC const &src_accum,
      KTileIterator k_tile_iter, int k_tile_count,
      ResidueMNK residue_mnk,
      int thread_idx,
      char *smem_buf)
  {
    using namespace cute;

    static_assert(is_rmem<FrgTensorD>::value, "D tensor must be rmem resident.");
    static_assert(is_gmem<TensorA>::value,    "A tensor must be gmem resident.");
    static_assert(is_gmem<TensorB>::value,    "B tensor must be gmem resident.");
    static_assert(is_rmem<FrgTensorC>::value, "C tensor must be rmem resident.");
    static_assert(rank(SmemLayoutA{}) == 3,
      "MainloopSm80CpAsync must have a pipeline mode in the smem layout.");
    static_assert(rank(SmemLayoutB{}) == 3,
      "MainloopSm80CpAsync must have a pipeline mode in the smem layout.");

    // Construct shared memory tiles
    SharedStorage& storage = *reinterpret_cast<SharedStorage*>(smem_buf);
    Tensor sA = make_tensor(make_smem_ptr(storage.smem_a.data()), SmemLayoutA{}); // (BLK_M,BLK_K,PIPE)
    Tensor sB = make_tensor(make_smem_ptr(storage.smem_b.data()), SmemLayoutB{}); // (BLK_N,BLK_K,PIPE)

    CUTE_STATIC_ASSERT_V(size<0>(gA) == size<0>(sA));                          // BLK_M
    CUTE_STATIC_ASSERT_V(size<1>(gA) == size<1>(sA));                          // BLK_K
    CUTE_STATIC_ASSERT_V(size<0>(gB) == size<0>(sB));                          // BLK_N
    CUTE_STATIC_ASSERT_V(size<1>(gB) == size<1>(sB));                          // BLK_K
    CUTE_STATIC_ASSERT_V(size<1>(sA) == size<1>(sB));                          // BLK_K
    CUTE_STATIC_ASSERT_V(Int<DispatchPolicy::Stages>{} == size<2>(sA));        // PIPE
    CUTE_STATIC_ASSERT_V(Int<DispatchPolicy::Stages>{} == size<2>(sB));        // PIPE

    // Partition the copying of A and B tiles across the threads
    GmemTiledCopyA gmem_tiled_copy_A;
    GmemTiledCopyB gmem_tiled_copy_B;
    auto gmem_thr_copy_A = gmem_tiled_copy_A.get_slice(thread_idx);
    auto gmem_thr_copy_B = gmem_tiled_copy_B.get_slice(thread_idx);

    Tensor tAgA = gmem_thr_copy_A.partition_S(gA);                             // (ACPY,ACPY_M,ACPY_K,k)
    Tensor tAsA = gmem_thr_copy_A.partition_D(sA);                             // (ACPY,ACPY_M,ACPY_K,PIPE)
    Tensor tBgB = gmem_thr_copy_B.partition_S(gB);                             // (BCPY,BCPY_N,BCPY_K,k)
    Tensor tBsB = gmem_thr_copy_B.partition_D(sB);                             // (BCPY,BCPY_N,BCPY_K,PIPE)

    //
    // PREDICATES
    //

    (void) residue_mnk;
    //assert(residue_mnk == make_tuple(0,0,0));

    //
    // PREFETCH
    //

    // Start async loads for all pipes but the last
    CUTLASS_PRAGMA_UNROLL
    for (int k_pipe = 0; k_pipe < DispatchPolicy::Stages-1; ++k_pipe) {
      copy(gmem_tiled_copy_A, tAgA(_,_,_,*k_tile_iter), tAsA(_,_,_,k_pipe));
      copy(gmem_tiled_copy_B, tBgB(_,_,_,*k_tile_iter), tBsB(_,_,_,k_pipe));
      cp_async_fence();
      --k_tile_count;
      if (k_tile_count > 0) { ++k_tile_iter; }
    }

    //
    // MMA Atom partitioning
    //

    // Tile MMA compute thread partitions and allocate accumulators
    TiledMma tiled_mma;
    auto thr_mma = tiled_mma.get_thread_slice(thread_idx);
    Tensor tCrA = thr_mma.partition_fragment_A(sA(_,_,0));                     // (MMA,MMA_M,MMA_K)
    Tensor tCrB = thr_mma.partition_fragment_B(sB(_,_,0));                     // (MMA,MMA_N,MMA_K)

    CUTE_STATIC_ASSERT_V(size<1>(tCrA) == size<1>(accum));                     // MMA_M
    CUTE_STATIC_ASSERT_V(size<1>(tCrA) == size<1>(src_accum));                 // MMA_M
    CUTE_STATIC_ASSERT_V(size<1>(tCrB) == size<2>(accum));                     // MMA_N
    CUTE_STATIC_ASSERT_V(size<1>(tCrB) == size<2>(src_accum));                 // MMA_N
    CUTE_STATIC_ASSERT_V(size<2>(tCrA) == size<2>(tCrB));                      // MMA_K
    CUTE_STATIC_ASSERT_V(size(gmem_tiled_copy_A) == size(tiled_mma));
    CUTE_STATIC_ASSERT_V(size(gmem_tiled_copy_B) == size(tiled_mma));

    //
    // Copy Atom retiling
    //

    auto smem_tiled_copy_A = make_tiled_copy_A(SmemCopyAtomA{}, tiled_mma);
    auto smem_thr_copy_A   = smem_tiled_copy_A.get_thread_slice(thread_idx);
    Tensor tCsA            = smem_thr_copy_A.partition_S(sA);                  // (CPY,CPY_M,CPY_K,PIPE)
    Tensor tCrA_copy_view  = smem_thr_copy_A.retile_D(tCrA);                   // (CPY,CPY_M,CPY_K)
    CUTE_STATIC_ASSERT_V(size<1>(tCsA) == size<1>(tCrA_copy_view));            // CPY_M
    CUTE_STATIC_ASSERT_V(size<2>(tCsA) == size<2>(tCrA_copy_view));            // CPY_K

    auto smem_tiled_copy_B = make_tiled_copy_B(SmemCopyAtomB{}, tiled_mma);
    auto smem_thr_copy_B   = smem_tiled_copy_B.get_thread_slice(thread_idx);
    Tensor tCsB            = smem_thr_copy_B.partition_S(sB);                  // (CPY,CPY_N,CPY_K,PIPE)
    Tensor tCrB_copy_view  = smem_thr_copy_B.retile_D(tCrB);                   // (CPY,CPY_N,CPY_K)
    CUTE_STATIC_ASSERT_V(size<1>(tCsB) == size<1>(tCrB_copy_view));            // CPY_N
    CUTE_STATIC_ASSERT_V(size<2>(tCsB) == size<2>(tCrB_copy_view));            // CPY_K

    //
    // PIPELINED MAIN LOOP
    //

    // Current pipe index in smem to read from
    int smem_pipe_read  = 0;
    // Current pipe index in smem to write to
    int smem_pipe_write = DispatchPolicy::Stages-1;

    Tensor tCsA_p = tCsA(_,_,_,smem_pipe_read);
    Tensor tCsB_p = tCsB(_,_,_,smem_pipe_read);

    // Size of the register pipeline
    auto K_BLOCK_MAX = size<2>(tCrA);

    // PREFETCH register pipeline
    if (K_BLOCK_MAX > 1) {
      // Wait until our first prefetched tile is loaded in
      cp_async_wait<DispatchPolicy::Stages-2>();
      __syncthreads();

      // Prefetch the first rmem from the first k-tile
      copy(smem_tiled_copy_A, tCsA_p(_,_,Int<0>{}), tCrA_copy_view(_,_,Int<0>{}));
      copy(smem_tiled_copy_B, tCsB_p(_,_,Int<0>{}), tCrB_copy_view(_,_,Int<0>{}));
    }


    CUTLASS_PRAGMA_NO_UNROLL
    for ( ; k_tile_count > -(DispatchPolicy::Stages-1); --k_tile_count)
    {
      // Pipeline the outer products with a static for loop.
      //
      // Note, the for_each() function is required here to ensure `k_block` is of type Int<x>.
      for_each(make_int_sequence<K_BLOCK_MAX>{}, [&] (auto k_block)
      {
        if (k_block == K_BLOCK_MAX - 1)
        {
          // Slice the smem_pipe_read smem
          tCsA_p = tCsA(_,_,_,smem_pipe_read);
          tCsB_p = tCsB(_,_,_,smem_pipe_read);

          // Commit the smem for smem_pipe_read
          cp_async_wait<DispatchPolicy::Stages-2>();
          __syncthreads();
        }

        // Load A, B shmem->regs for k_block+1
        auto k_block_next = (k_block + Int<1>{}) % K_BLOCK_MAX;  // static
        copy(smem_tiled_copy_A, tCsA_p(_,_,k_block_next), tCrA_copy_view(_,_,k_block_next));
        copy(smem_tiled_copy_B, tCsB_p(_,_,k_block_next), tCrB_copy_view(_,_,k_block_next));
        // Copy gmem to smem before computing gemm on each k-pipe
        if (k_block == 0)
        {
          copy(gmem_tiled_copy_A, tAgA(_,_,_,*k_tile_iter), tAsA(_,_,_,smem_pipe_write));
          copy(gmem_tiled_copy_B, tBgB(_,_,_,*k_tile_iter), tBsB(_,_,_,smem_pipe_write));
          cp_async_fence();
          if (k_tile_count > 0) { ++k_tile_iter; }

          // Advance the pipe -- Doing it here accounts for K_BLOCK_MAX = 1 (no rmem pipe)
          smem_pipe_write = smem_pipe_read;
          ++smem_pipe_read;
          smem_pipe_read = (smem_pipe_read == DispatchPolicy::Stages) ? 0 : smem_pipe_read;
        }

        // Transform before compute
        cute::transform(tCrA(_,_,k_block), TransformA{});
        cute::transform(tCrB(_,_,k_block), TransformB{});
        // Thread-level register gemm for k_block
        cute::gemm(tiled_mma, accum, tCrA(_,_,k_block), tCrB(_,_,k_block), src_accum);
      });

    }
  }
};

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

template <
  int Stages,
  class TileShape_,
  class ElementA_,
  class StrideA_,
  class ElementB_,
  class StrideB_,
  class TiledMma_,
  class GmemTiledCopyA_,
  class SmemLayoutAtomA_,
  class SmemCopyAtomA_,
  class TransformA_,
  class GmemTiledCopyB_,
  class SmemLayoutAtomB_,
  class SmemCopyAtomB_,
  class TransformB_>
struct CollectiveMma<
    MainloopSm80CpAsync<Stages>,
    TileShape_,
    ElementA_,
    StrideA_,
    ElementB_,
    StrideB_,
    TiledMma_,
    GmemTiledCopyA_,
    SmemLayoutAtomA_,
    SmemCopyAtomA_,
    TransformA_,
    GmemTiledCopyB_,
    SmemLayoutAtomB_,
    SmemCopyAtomB_,
    TransformB_>
{
  //
  // Type Aliases
  //
  using DispatchPolicy = MainloopSm80CpAsync<Stages>;
  using TileShape = TileShape_;
  using ElementA = ElementA_;
  using StrideA = StrideA_;
  using ElementB = ElementB_;
  using StrideB = StrideB_;
  using TiledMma = TiledMma_;
  using ElementAccumulator = typename TiledMma::ValTypeC;  using GmemTiledCopyA = GmemTiledCopyA_;
  using GmemTiledCopyB = GmemTiledCopyB_;
  using SmemLayoutAtomA = SmemLayoutAtomA_;
  using SmemLayoutAtomB = SmemLayoutAtomB_;
  using SmemCopyAtomA = SmemCopyAtomA_;
  using SmemCopyAtomB = SmemCopyAtomB_;
  using TransformA = TransformA_;
  using TransformB = TransformB_;
  using ArchTag = typename DispatchPolicy::ArchTag;

  static_assert(rank(SmemLayoutAtomA{}) == 2, "SmemLayoutAtom must be rank 2 (M/N, K)");
  static_assert((size<0>(TileShape{}) % size<0>(SmemLayoutAtomA{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");
  static_assert((size<2>(TileShape{}) % size<1>(SmemLayoutAtomA{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");

  static_assert(rank(SmemLayoutAtomB{}) == 2, "SmemLayoutAtom must be rank 2 (M/N, K)");
  static_assert((size<1>(TileShape{}) % size<0>(SmemLayoutAtomB{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");
  static_assert((size<2>(TileShape{}) % size<1>(SmemLayoutAtomB{})) == 0, "SmemLayoutAtom must evenly divide tile shape.");

  using SmemLayoutA = decltype(tile_to_shape(
      SmemLayoutAtomA{},
      make_shape(shape<0>(TileShape{}), shape<2>(TileShape{}), Int<DispatchPolicy::Stages>{})));
  using SmemLayoutB = decltype(tile_to_shape(
      SmemLayoutAtomB{},
      make_shape(shape<1>(TileShape{}), shape<2>(TileShape{}), Int<DispatchPolicy::Stages>{})));

  static_assert(DispatchPolicy::Stages >= 2, "CpAsync mainloop must have at least 2 stages in the pipeline.");

  struct SharedStorage
  {
    cute::array_aligned<ElementA, cute::cosize_v<SmemLayoutA>> smem_a;
    cute::array_aligned<ElementB, cute::cosize_v<SmemLayoutB>> smem_b;
  };

  struct Params {
    ElementA const* ptr_A;
    StrideA dA;
    ElementB const* ptr_B;
    StrideB dB;
  };

  //
  // Methods
  //

  CollectiveMma() = default;

  template <class Args>
  static constexpr Params
  to_underlying_arguments(Args const& args, void* workspace) {
    (void) workspace;
    return {args.ptr_A, args.dA, args.ptr_B, args.dB};
  }

  /// Perform a collective-scoped matrix multiply-accumulate
  template <
    class FrgTensorD,
    class TensorA,
    class TensorB,
    class FrgTensorC,
    class KTileIterator,
    class ResidueMNK
  >
  CUTLASS_DEVICE void
  operator() (
      FrgTensorD &accum,
      TensorA gA,                   // (BLK_M, BLK_K, K_TILES)
      TensorB gB,                   // (BLK_N, BLK_K, K_TILES)
      FrgTensorC const &src_accum,
      KTileIterator k_tile_iter, int k_tile_count,
      ResidueMNK residue_mnk,
      int thread_idx,
      char *smem_buf)
  {
    using namespace cute;

    static_assert(is_rmem<FrgTensorD>::value, "D tensor must be rmem resident.");
    static_assert(is_gmem<TensorA>::value,    "A tensor must be gmem resident.");
    static_assert(is_gmem<TensorB>::value,    "B tensor must be gmem resident.");
    static_assert(is_rmem<FrgTensorC>::value, "C tensor must be rmem resident.");
    static_assert(rank(SmemLayoutA{}) == 3, "Smem layout must be rank 3.");
    static_assert(rank(SmemLayoutB{}) == 3, "Smem layout must be rank 3.");

    // Construct shared memory tiles
    SharedStorage& storage = *reinterpret_cast<SharedStorage*>(smem_buf);
    Tensor sA = make_tensor(make_smem_ptr(storage.smem_a.data()), SmemLayoutA{}); // (BLK_M,BLK_K,PIPE)
    Tensor sB = make_tensor(make_smem_ptr(storage.smem_b.data()), SmemLayoutB{}); // (BLK_N,BLK_K,PIPE)

    CUTE_STATIC_ASSERT_V(size<0>(gA) == size<0>(sA));                          // BLK_M
    CUTE_STATIC_ASSERT_V(size<1>(gA) == size<1>(sA));                          // BLK_K
    CUTE_STATIC_ASSERT_V(size<0>(gB) == size<0>(sB));                          // BLK_N
    CUTE_STATIC_ASSERT_V(size<1>(gB) == size<1>(sB));                          // BLK_K
    CUTE_STATIC_ASSERT_V(size<1>(sA) == size<1>(sB));                          // BLK_K
    CUTE_STATIC_ASSERT_V(Int<DispatchPolicy::Stages>{} == size<2>(sA));        // PIPE
    CUTE_STATIC_ASSERT_V(Int<DispatchPolicy::Stages>{} == size<2>(sB));        // PIPE

    // Shift tensor so residue_k is at origin (Can't read any k_coord < residue_k)
    // This aligns the tensor with BLK_K for all but the 0th k_tile
    gA.data() = &gA(0, get<2>(residue_mnk), 0);
    gB.data() = &gB(0, get<2>(residue_mnk), 0);

    // Partition the copying of A and B tiles across the threads
    GmemTiledCopyA gmem_tiled_copy_A;
    GmemTiledCopyB gmem_tiled_copy_B;
    auto gmem_thr_copy_A = gmem_tiled_copy_A.get_slice(thread_idx);
    auto gmem_thr_copy_B = gmem_tiled_copy_B.get_slice(thread_idx);

    Tensor tAgA = gmem_thr_copy_A.partition_S(gA);                             // (ACPY,ACPY_M,ACPY_K,k)
    Tensor tAsA = gmem_thr_copy_A.partition_D(sA);                             // (ACPY,ACPY_M,ACPY_K,PIPE)
    Tensor tBgB = gmem_thr_copy_B.partition_S(gB);                             // (BCPY,BCPY_N,BCPY_K,k)
    Tensor tBsB = gmem_thr_copy_B.partition_D(sB);                             // (BCPY,BCPY_N,BCPY_K,PIPE)

    //
    // PREDICATES
    //

    // Allocate predicate tensors for m and n
    Tensor tApA = make_tensor<bool>(make_shape(size<1>(tAsA), size<2>(tAsA)), Stride<_1,_0>{});
    Tensor tBpB = make_tensor<bool>(make_shape(size<1>(tBsB), size<2>(tBsB)), Stride<_1,_0>{});

    // Construct identity layout for sA and sB
    Tensor cA = make_identity_tensor(make_shape(size<0>(sA), size<1>(sA)));    // (BLK_M,BLK_K) -> (blk_m,blk_k)
    Tensor cB = make_identity_tensor(make_shape(size<0>(sB), size<1>(sB)));    // (BLK_N,BLK_K) -> (blk_n,blk_k)

    // Repeat the partitioning with identity layouts
    Tensor tAcA = gmem_thr_copy_A.partition_S(cA);                             // (ACPY,ACPY_M,ACPY_K) -> (blk_m,blk_k)
    Tensor tBcB = gmem_thr_copy_B.partition_S(cB);                             // (BCPY,BCPY_N,BCPY_K) -> (blk_n,blk_k)

    // Set predicates for m bounds
    CUTLASS_PRAGMA_UNROLL
    for (int m = 0; m < size<0>(tApA); ++m) {
      tApA(m,0) = get<0>(tAcA(0,m,0)) < get<0>(residue_mnk);  // blk_m coord < residue_m
    }
    // Set predicates for n bounds
    CUTLASS_PRAGMA_UNROLL
    for (int n = 0; n < size<0>(tBpB); ++n) {
      tBpB(n,0) = get<0>(tBcB(0,n,0)) < get<1>(residue_mnk);  // blk_n coord < residue_n
    }

    //
    // PREFETCH
    //

    // Clear the smem tiles to account for predicated off loads
    clear(tAsA);
    clear(tBsB);

    // Start async loads for 0th k-tile, where we take care of the k residue
    {
      constexpr int k_pipe = 0;

      Tensor tAgAk = tAgA(_,_,_,*k_tile_iter);
      CUTLASS_PRAGMA_UNROLL
      for (int k = 0; k < size<2>(tAsA); ++k) {
        if (get<1>(tAcA(0,0,k)) >= -get<2>(residue_mnk)) {      // blk_k coord < residue_k (gA shifted)
          copy_if(gmem_tiled_copy_A, tApA(_,k), tAgAk(_,_,k), tAsA(_,_,k,k_pipe));
        }
      }
      Tensor tBgBk = tBgB(_,_,_,*k_tile_iter);
      CUTLASS_PRAGMA_UNROLL
      for (int k = 0; k < size<2>(tBsB); ++k) {
        if (get<1>(tBcB(0,0,k)) >= -get<2>(residue_mnk)) {      // blk_k coord < residue_k (gB shifted)
          copy_if(gmem_tiled_copy_B, tBpB(_,k), tBgBk(_,_,k), tBsB(_,_,k,k_pipe));
        }
      }
      cp_async_fence();
      ++k_tile_iter;
      --k_tile_count;
    }

    // Start async loads for 1st k-tile onwards, no k-residue handling needed
    CUTLASS_PRAGMA_UNROLL
    for (int k_pipe = 1; k_pipe < DispatchPolicy::Stages-1; ++k_pipe) {
      if (k_tile_count <= 0) {
        clear(tApA);
        clear(tBpB);
      }
      copy_if(gmem_tiled_copy_A, tApA, tAgA(_,_,_,*k_tile_iter), tAsA(_,_,_,k_pipe));  // CpAsync
      copy_if(gmem_tiled_copy_B, tBpB, tBgB(_,_,_,*k_tile_iter), tBsB(_,_,_,k_pipe));  // CpAsync
      cp_async_fence();
      ++k_tile_iter;
      --k_tile_count;
    }

    //
    // MMA Atom partitioning
    //

    // Tile MMA compute thread partitions and allocate accumulators
    TiledMma tiled_mma;
    auto thr_mma = tiled_mma.get_thread_slice(thread_idx);
    Tensor tCrA  = thr_mma.partition_fragment_A(sA(_,_,0));                    // (MMA,MMA_M,MMA_K)
    Tensor tCrB  = thr_mma.partition_fragment_B(sB(_,_,0));                    // (MMA,MMA_N,MMA_K)

    CUTE_STATIC_ASSERT_V(size<1>(tCrA) == size<1>(accum));                     // MMA_M
    CUTE_STATIC_ASSERT_V(size<1>(tCrA) == size<1>(src_accum));                 // MMA_M
    CUTE_STATIC_ASSERT_V(size<1>(tCrB) == size<2>(accum));                     // MMA_N
    CUTE_STATIC_ASSERT_V(size<1>(tCrB) == size<2>(src_accum));                 // MMA_N
    CUTE_STATIC_ASSERT_V(size<2>(tCrA) == size<2>(tCrB));                      // MMA_K

    //
    // Copy Atom retiling
    //

    auto smem_tiled_copy_A   = make_tiled_copy_A(SmemCopyAtomA{}, tiled_mma);
    auto smem_thr_copy_A     = smem_tiled_copy_A.get_thread_slice(thread_idx);
    Tensor tCsA           = smem_thr_copy_A.partition_S(sA);                   // (CPY,CPY_M,CPY_K,PIPE)
    Tensor tCrA_copy_view = smem_thr_copy_A.retile_D(tCrA);                    // (CPY,CPY_M,CPY_K)
    CUTE_STATIC_ASSERT_V(size<1>(tCsA) == size<1>(tCrA_copy_view));            // CPY_M
    CUTE_STATIC_ASSERT_V(size<2>(tCsA) == size<2>(tCrA_copy_view));            // CPY_K

    auto smem_tiled_copy_B = make_tiled_copy_B(SmemCopyAtomB{}, tiled_mma);
    auto smem_thr_copy_B   = smem_tiled_copy_B.get_thread_slice(thread_idx);
    Tensor tCsB              = smem_thr_copy_B.partition_S(sB);                // (CPY,CPY_N,CPY_K,PIPE)
    Tensor tCrB_copy_view    = smem_thr_copy_B.retile_D(tCrB);                 // (CPY,CPY_N,CPY_K)
    CUTE_STATIC_ASSERT_V(size<1>(tCsB) == size<1>(tCrB_copy_view));            // CPY_N
    CUTE_STATIC_ASSERT_V(size<2>(tCsB) == size<2>(tCrB_copy_view));            // CPY_K

    //
    // PIPELINED MAIN LOOP
    //

    // Current pipe index in smem to read from
    int smem_pipe_read  = 0;
    // Current pipe index in smem to write to
    int smem_pipe_write = DispatchPolicy::Stages-1;

    Tensor tCsA_p = tCsA(_,_,_,smem_pipe_read);
    Tensor tCsB_p = tCsB(_,_,_,smem_pipe_read);

    // Size of the register pipeline
    auto K_BLOCK_MAX = size<2>(tCrA);

    // PREFETCH register pipeline
    if (K_BLOCK_MAX > 1) {
      // Wait until our first prefetched tile is loaded in
      cp_async_wait<DispatchPolicy::Stages-2>();
      __syncthreads();

      // Prefetch the first rmem from the first k-tile
      copy(smem_tiled_copy_A, tCsA_p(_,_,Int<0>{}), tCrA_copy_view(_,_,Int<0>{}));
      copy(smem_tiled_copy_B, tCsB_p(_,_,Int<0>{}), tCrB_copy_view(_,_,Int<0>{}));
    }


    CUTLASS_PRAGMA_NO_UNROLL
    for ( ; k_tile_count > -(DispatchPolicy::Stages-1); --k_tile_count)
    {
      // Pipeline the outer products with a static for loop.
      //
      // Note, the for_each() function is required here to ensure `k_block` is of type Int<N>.
      for_each(make_int_sequence<K_BLOCK_MAX>{}, [&] (auto k_block)
      {
        if (k_block == K_BLOCK_MAX - 1)
        {
          // Slice the smem_pipe_read smem
          tCsA_p = tCsA(_,_,_,smem_pipe_read);
          tCsB_p = tCsB(_,_,_,smem_pipe_read);

          // Commit the smem for smem_pipe_read
          cp_async_wait<DispatchPolicy::Stages-2>();
          __syncthreads();
        }

        // Load A, B shmem->regs for k_block+1
        auto k_block_next = (k_block + Int<1>{}) % K_BLOCK_MAX;  // static
        copy(smem_tiled_copy_A, tCsA_p(_,_,k_block_next), tCrA_copy_view(_,_,k_block_next));
        copy(smem_tiled_copy_B, tCsB_p(_,_,k_block_next), tCrB_copy_view(_,_,k_block_next));
        // Copy gmem to smem before computing gemm on each k-pipe
        if (k_block == 0)
        {
          // Set all predicates to false if we are going to overshoot bounds
          if (k_tile_count <= 0) {
            clear(tApA);
            clear(tBpB);
          }
          copy_if(gmem_tiled_copy_A, tApA, tAgA(_,_,_,*k_tile_iter), tAsA(_,_,_,smem_pipe_write));
          copy_if(gmem_tiled_copy_B, tBpB, tBgB(_,_,_,*k_tile_iter), tBsB(_,_,_,smem_pipe_write));
          cp_async_fence();
          ++k_tile_iter;

          // Advance the pipe -- Doing it here accounts for K_BLOCK_MAX = 1 (no rmem pipe)
          smem_pipe_write = smem_pipe_read;
          ++smem_pipe_read;
          smem_pipe_read = (smem_pipe_read == DispatchPolicy::Stages) ? 0 : smem_pipe_read;
        }

        // Transform before compute
        cute::transform(tCrA(_,_,k_block), TransformA{});
        cute::transform(tCrB(_,_,k_block), TransformB{});
        // Thread-level register gemm for k_block
        cute::gemm(tiled_mma, accum, tCrA(_,_,k_block), tCrB(_,_,k_block), src_accum);
      });

    }
  }
};

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

} // namespace cutlass::gemm::collective

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