flash-attention/csrc/cutlass/include/cute/arch/copy_sm80.hpp

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#pragma once

#include <cute/config.hpp>

#include <cute/arch/copy.hpp>

// Config
#if (defined(__CUDA_ARCH__) && (__CUDA_ARCH__ >= 800))
#  define CUTE_ARCH_CP_ASYNC_SM80_ENABLED
#endif

namespace cute
{

/// Copy via cp.async with caching at all levels
template <class TS, class TD = TS>
struct SM80_CP_ASYNC_CACHEALWAYS
{
  using SRegisters = TS[1];
  using DRegisters = TD[1];

  static_assert(sizeof(TS) == sizeof(TD), "cp.async requires sizeof(src_value_type) == sizeof(dst_value_type)");
  static_assert(sizeof(TS) == 4 || sizeof(TS) == 8 || sizeof(TS) == 16, "cp.async sizeof(TS) is not supported");

  CUTE_HOST_DEVICE static void
  copy(TS const& gmem_src,
       TD      & smem_dst)
  {
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
    TS const* gmem_ptr    = &gmem_src;
    uint32_t smem_int_ptr = cast_smem_ptr_to_uint(&smem_dst);
    asm volatile("cp.async.ca.shared.global.L2::128B [%0], [%1], %2;\n"
        :: "r"(smem_int_ptr),
           "l"(gmem_ptr),
           "n"(sizeof(TS)));
#else
    CUTE_INVALID_CONTROL_PATH("Support for cp.async instructions has not been enabled");
#endif
  }
};

/// Copy via cp.async with caching at global level
template <class TS, class TD = TS>
struct SM80_CP_ASYNC_CACHEGLOBAL
{
  using SRegisters = TS[1];
  using DRegisters = TD[1];

  static_assert(sizeof(TS) == sizeof(TD), "cp.async requires sizeof(src_value_type) == sizeof(dst_value_type)");
  static_assert(sizeof(TS) == 4 || sizeof(TS) == 8 || sizeof(TS) == 16, "cp.async sizeof(TS) is not supported");

  CUTE_HOST_DEVICE static void
  copy(TS const& gmem_src,
       TD      & smem_dst)
  {
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
    TS const* gmem_ptr    = &gmem_src;
    uint32_t smem_int_ptr = cast_smem_ptr_to_uint(&smem_dst);
    asm volatile("cp.async.cg.shared.global.L2::128B [%0], [%1], %2;\n"
        :: "r"(smem_int_ptr),
           "l"(gmem_ptr),
           "n"(sizeof(TS)));
#else
    CUTE_INVALID_CONTROL_PATH("Support for cp.async instructions has not been enabled");
#endif
  }
};

/// Copy via cp.async with caching at all levels
template <class TS, class TD = TS>
struct SM80_CP_ASYNC_CACHEALWAYS_ZFILL
{
  using SRegisters = TS[1];
  using DRegisters = TD[1];

  static_assert(sizeof(TS) == sizeof(TD), "cp.async requires sizeof(src_value_type) == sizeof(dst_value_type)");
  static_assert(sizeof(TS) == 4 || sizeof(TS) == 8 || sizeof(TS) == 16, "cp.async sizeof(TS) is not supported");

  CUTE_HOST_DEVICE static void
  copy(TS const& gmem_src,
       TD      & smem_dst,
       bool      pred)
  {
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
    TS const* gmem_ptr    = &gmem_src;
    uint32_t smem_int_ptr = cast_smem_ptr_to_uint(&smem_dst);
    int src_size = pred ? sizeof(TS) : 0;
    asm volatile("cp.async.ca.shared.global.L2::128B [%0], [%1], %2, %3;\n"
        :: "r"(smem_int_ptr),
           "l"(gmem_ptr),
           "n"(sizeof(TS)),
           "r"(src_size));
#else
    CUTE_INVALID_CONTROL_PATH("Support for cp.async instructions has not been enabled");
#endif
  }
};

/// Copy via cp.async with caching at global level
template <class TS, class TD = TS>
struct SM80_CP_ASYNC_CACHEGLOBAL_ZFILL
{
  using SRegisters = TS[1];
  using DRegisters = TD[1];

  static_assert(sizeof(TS) == sizeof(TD), "cp.async requires sizeof(src_value_type) == sizeof(dst_value_type)");
  static_assert(sizeof(TS) == 4 || sizeof(TS) == 8 || sizeof(TS) == 16, "cp.async sizeof(TS) is not supported");

  CUTE_HOST_DEVICE static void
  copy(TS const& gmem_src,
       TD      & smem_dst,
       bool      pred)
  {
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
    TS const* gmem_ptr    = &gmem_src;
    uint32_t smem_int_ptr = cast_smem_ptr_to_uint(&smem_dst);
    int src_size = pred ? sizeof(TS) : 0;
    asm volatile("cp.async.cg.shared.global.L2::128B [%0], [%1], %2, %3;\n"
        :: "r"(smem_int_ptr),
           "l"(gmem_ptr),
           "n"(sizeof(TS)),
           "r"(src_size));
#else
    CUTE_INVALID_CONTROL_PATH("Support for cp.async instructions has not been enabled");
#endif
  }
};

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

/// Establishes an ordering w.r.t previously issued cp.async instructions. Does not block.
CUTE_HOST_DEVICE
void
cp_async_fence()
{
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
  asm volatile("cp.async.commit_group;\n" ::);
#endif
}

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

/// Blocks until all but N previous cp.async.commit_group operations have committed.
template <int N>
CUTE_HOST_DEVICE
void
cp_async_wait()
{
#if defined(CUTE_ARCH_CP_ASYNC_SM80_ENABLED)
  if constexpr (N == 0) {
    asm volatile("cp.async.wait_all;\n" ::);
  } else {
    asm volatile("cp.async.wait_group %0;\n" :: "n"(N));
  }
#endif
}

template <int N>
CUTE_HOST_DEVICE
void
cp_async_wait(Int<N>)
{
  return cp_async_wait<N>();
}

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

} // end namespace cute