flash-attention/csrc/cutlass/include/cute/arch/copy_sm50.hpp

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#pragma once

#include <cute/config.hpp>

#include <cute/arch/copy.hpp>

#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 500
  #define CUTE_ARCH_WARP_SHUFFLE_ENABLED 1
#endif

namespace cute
{

struct SM50_Shuffle_U32_2x2Trans
{
  using SRegisters = uint32_t[2];
  using DRegisters = uint32_t[2];

  CUTE_HOST_DEVICE static void
  copy(uint32_t const& src0, uint32_t const& src1, uint32_t& dst0, uint32_t& dst1)
  {
#if defined(CUTE_ARCH_WARP_SHUFFLE_ENABLED)
    uint32_t x0 = src0;
    uint32_t y0 = __shfl_xor_sync(0xffffffff, x0, 1);

    uint32_t x1 = src1;
    uint32_t y1 = __shfl_xor_sync(0xffffffff, x1, 1);

    if (threadIdx.x % 2 == 0) {
      dst1 = y0;
    } 
    else {
      dst0 = y1;
    }
#else 
    CUTE_INVALID_CONTROL_PATH("Trying to use __shfl_xor_sync without CUTE_ARCH_WARP_SHUFFLE_ENABLED.");
#endif
  }
};


} // end namespace cute