ptx.cuh

/*************************************************************************
 * Copyright (c) 2022-2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 *
 * See LICENSE for license information.
 ************************************************************************/

/*! \file ptx.cuh
 *  \brief BW PTX
 */

#ifndef TRANSFORMER_ENGINE_PTX_CUH_
#define TRANSFORMER_ENGINE_PTX_CUH_

#include <cuda.h>
#include <cuda_runtime.h>

namespace transformer_engine {
namespace ptx {

#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#parallel-synchronization-and-communication-instructions-mbarrier-init
__device__ __forceinline__ void mbarrier_init(uint64_t *mbar, const uint32_t count) {
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  asm volatile("mbarrier.init.shared.b64 [%0], %1;" ::"r"(mbar_ptr), "r"(count) : "memory");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#parallel-synchronization-and-communication-instructions-mbarrier-inval
__device__ __forceinline__ void mbarrier_invalid(uint64_t *mbar) {
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  asm volatile("mbarrier.inval.shared.b64 [%0];" ::"r"(mbar_ptr) : "memory");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#parallel-synchronization-and-communication-instructions-mbarrier-arrive
__device__ __forceinline__ void mbarrier_arrive(uint64_t *mbar) {
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  asm volatile("mbarrier.arrive.shared.b64 _, [%0];" ::"r"(mbar_ptr) : "memory");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#parallel-synchronization-and-communication-instructions-mbarrier-arrive
__device__ __forceinline__ void mbarrier_arrive_expect_tx(uint64_t *mbar, const uint32_t tx_count) {
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  asm volatile("mbarrier.arrive.expect_tx.shared.b64 _, [%0], %1;" ::"r"(mbar_ptr), "r"(tx_count)
               : "memory");
}

__device__ __forceinline__ void fence_mbarrier_init_release_cluster() {
  asm volatile("fence.mbarrier_init.release.cluster;");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-tensor
// global -> shared::cluster
__device__ __forceinline__ void cp_async_bulk_tensor_1d_global_to_shared(
    uint64_t *dst_shmem, const uint64_t *src_global_ptr, const uint32_t size, uint64_t *mbar) {
  uint32_t dst_shmem_ptr = __cvta_generic_to_shared(dst_shmem);
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  // triggers async copy, i.e. the thread continues until wait() on mbarrier
  // barrier condition:
  // - leader must arrive (i.e. 1 thread as set above)
  // - TMA hardware substracts bytes from expect_tx counter, must reach zero
  asm volatile(
      "cp.async.bulk.shared::cta.global"
      ".mbarrier::complete_tx::bytes [%0], [%1], %2, [%3];" ::"r"(dst_shmem_ptr),
      "l"(src_global_ptr), "r"(size), "r"(mbar_ptr)
      : "memory");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-tensor
// global -> shared::cluster
__device__ __forceinline__ void cp_async_bulk_tensor_2d_global_to_shared(
    uint64_t *dst_shmem, const uint64_t *tensor_map_ptr, const uint32_t offset_x,
    const uint32_t offset_y, uint64_t *mbar) {
  uint32_t dst_shmem_ptr = __cvta_generic_to_shared(dst_shmem);
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  // triggers async copy, i.e. the thread continues until wait() on mbarrier
  // barrier condition:
  // - leader must arrive (i.e. 1 thread as set above)
  // - TMA hardware substracts bytes from expect_tx counter, must reach zero
  asm volatile(
      "cp.async.bulk.tensor.2d.shared::cluster.global.tile"
      ".mbarrier::complete_tx::bytes [%0], [%1, {%2, %3}], [%4];" ::"r"(dst_shmem_ptr),
      "l"(tensor_map_ptr), "r"(offset_x), "r"(offset_y), "r"(mbar_ptr)
      : "memory");
}

__device__ __forceinline__ bool mbarrier_try_wait_parity(uint32_t mbar_ptr, const uint32_t parity) {
  uint32_t waitComplete;
  asm volatile(
      "{\n\t .reg .pred P_OUT; \n\t"
      "mbarrier.try_wait.parity.shared::cta.b64  P_OUT, [%1], %2; \n\t"
      "selp.b32 %0, 1, 0, P_OUT; \n"
      "}"
      : "=r"(waitComplete)
      : "r"(mbar_ptr), "r"(parity)
      : "memory");
  return static_cast<bool>(waitComplete);
}

__device__ __forceinline__ void mbarrier_wait_parity(uint64_t *mbar, const uint32_t parity) {
  uint32_t mbar_ptr = __cvta_generic_to_shared(mbar);
  while (!mbarrier_try_wait_parity(mbar_ptr, parity)) {
  }
}

#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)

#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 900)

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-tensor
// shared::cta -> global
__device__ __forceinline__ void cp_async_bulk_tensor_1d_shared_to_global(uint64_t *dst_global_ptr,
                                                                         const uint64_t *src_shmem,
                                                                         const uint32_t size) {
  uint32_t src_shmem_ptr = __cvta_generic_to_shared(src_shmem);
  asm volatile("cp.async.bulk.global.shared::cta.bulk_group [%0], [%1], %2;" ::"l"(dst_global_ptr),
               "r"(src_shmem_ptr), "r"(size)
               : "memory");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-tensor
// shared::cta -> global
__device__ __forceinline__ void cp_async_bulk_tensor_2d_shared_to_global(
    const uint64_t *tensor_map_ptr, const uint32_t offset_x, const uint32_t offset_y,
    uint64_t *src_shmem) {
  uint32_t src_shmem_ptr = __cvta_generic_to_shared(src_shmem);
  asm volatile("cp.async.bulk.tensor.2d.global.shared::cta.bulk_group [%0, {%1, %2}], [%3];" ::"l"(
                   tensor_map_ptr),
               "r"(offset_x), "r"(offset_y), "r"(src_shmem_ptr)
               : "memory");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-wait-group
__device__ __forceinline__ void cp_async_bulk_wait_group() {
  asm volatile("cp.async.bulk.wait_group 0;");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-wait-group
template <size_t W>
__device__ __forceinline__ void cp_async_bulk_wait_group_read() {
  asm volatile("cp.async.bulk.wait_group.read 0;");
}

template <>
__device__ __forceinline__ void cp_async_bulk_wait_group_read<0>() {
  asm volatile("cp.async.bulk.wait_group.read 0;");
}
template <>
__device__ __forceinline__ void cp_async_bulk_wait_group_read<1>() {
  asm volatile("cp.async.bulk.wait_group.read 1;");
}
template <>
__device__ __forceinline__ void cp_async_bulk_wait_group_read<2>() {
  asm volatile("cp.async.bulk.wait_group.read 2;");
}
template <>
__device__ __forceinline__ void cp_async_bulk_wait_group_read<4>() {
  asm volatile("cp.async.bulk.wait_group.read 4;");
}

// https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#data-movement-and-conversion-instructions-cp-async-bulk-commit-group
__device__ __forceinline__ void cp_async_bulk_commit_group() {
  asm volatile("cp.async.bulk.commit_group;");
}

// Proxy fence (bi-directional):
__device__ __forceinline__ void fence_proxy_async() { asm volatile("fence.proxy.async;"); }

__device__ __forceinline__ void fence_proxy_async_shared_cta() {
  asm volatile("fence.proxy.async.shared::cta;");
}

#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 900)

}  // namespace ptx

namespace {

template <int num_barriers, int THREADS_PER_BLOCK>
__forceinline__ __device__ void initialize_barriers(uint64_t *mbar, const bool is_master_thread) {
#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
  if (is_master_thread) {
    // Initialize barrier. All `blockDim.x * blockDim.y` threads in block participate.
#pragma unroll
    for (int iter = 0; iter < num_barriers; ++iter) {
      ptx::mbarrier_init(&mbar[iter], THREADS_PER_BLOCK);
    }
    ptx::fence_proxy_async_shared_cta();
  }
  // Syncthreads so initialized barrier is visible to all threads.
  __syncthreads();
#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
}

template <int num_barriers>
__forceinline__ __device__ void destroy_barriers(uint64_t *mbar, const bool is_master_thread) {
#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
  // Destroy barrier. This invalidates the memory region of the barrier. If
  // further computations were to take place in the kernel, this allows the
  // memory location of the shared memory barrier to be reused.
  if (is_master_thread) {
#pragma unroll
    for (int iter = 0; iter < num_barriers; ++iter) {
      ptx::mbarrier_invalid(&mbar[iter]);
    }
  }
#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
}

__forceinline__ __device__ void copy_1d_to_shared(void *dst, const void *src,
                                                  const size_t num_bytes, uint64_t *barrier,
                                                  const bool is_master_thread) {
#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
  if (is_master_thread) {
    // Initiate bulk tensor copy
    ptx::cp_async_bulk_tensor_1d_global_to_shared(reinterpret_cast<uint64_t *>(dst),
                                                  reinterpret_cast<const uint64_t *>(src),
                                                  num_bytes, barrier);

    // Arrive on the barrier and tell how many bytes are expected to come in.
    ptx::mbarrier_arrive_expect_tx(barrier, num_bytes);
  } else {
    // Other threads just arrive
    ptx::mbarrier_arrive(barrier);
  }
#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
}

__forceinline__ __device__ void copy_2d_to_shared(void *dst, const void *src, const size_t chunk_X,
                                                  const size_t chunk_Y, const size_t num_bytes,
                                                  uint64_t *barrier, const bool is_master_thread) {
#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
  if (is_master_thread) {
    // Initiate bulk tensor copy
    ptx::cp_async_bulk_tensor_2d_global_to_shared(reinterpret_cast<uint64_t *>(dst),
                                                  reinterpret_cast<const uint64_t *>(src), chunk_X,
                                                  chunk_Y, barrier);

    // Arrive on the barrier and tell how many bytes are expected to come in.
    ptx::mbarrier_arrive_expect_tx(barrier, num_bytes);
  } else {
    // Other threads just arrive
    ptx::mbarrier_arrive(barrier);
  }
#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
}

__forceinline__ __device__ void copy_2d_to_sharedx2(void *dst, const void *src,
                                                    const size_t chunk_X1, const size_t chunk_Y1,
                                                    void *dst2, const void *src2,
                                                    const size_t chunk_X2, const size_t chunk_Y2,
                                                    const size_t num_bytes, uint64_t *barrier,
                                                    const bool is_master_thread) {
#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
  if (is_master_thread) {
    // Initiate bulk tensor copy
    ptx::cp_async_bulk_tensor_2d_global_to_shared(reinterpret_cast<uint64_t *>(dst),
                                                  reinterpret_cast<const uint64_t *>(src), chunk_X1,
                                                  chunk_Y1, barrier);

    ptx::cp_async_bulk_tensor_2d_global_to_shared(reinterpret_cast<uint64_t *>(dst2),
                                                  reinterpret_cast<const uint64_t *>(src2),
                                                  chunk_X2, chunk_Y2, barrier);

    // Arrive on the barrier and tell how many bytes are expected to come in.
    ptx::mbarrier_arrive_expect_tx(barrier, 2 * num_bytes);
  } else {
    // Other threads just arrive
    ptx::mbarrier_arrive(barrier);
  }
#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
}

__forceinline__ __device__ void copy_2d_to_sharedx3(
    void *dst, const void *src, const size_t chunk_X1, const size_t chunk_Y1, void *dst2,
    const void *src2, const size_t chunk_X2, const size_t chunk_Y2, void *dst3, const void *src3,
    const size_t chunk_X3, const size_t chunk_Y3, const size_t num_bytes, uint64_t *barrier,
    const bool is_master_thread) {
#if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
  if (is_master_thread) {
    // Initiate bulk tensor copy
    ptx::cp_async_bulk_tensor_2d_global_to_shared(reinterpret_cast<uint64_t *>(dst),
                                                  reinterpret_cast<const uint64_t *>(src), chunk_X1,
                                                  chunk_Y1, barrier);

    ptx::cp_async_bulk_tensor_2d_global_to_shared(reinterpret_cast<uint64_t *>(dst2),
                                                  reinterpret_cast<const uint64_t *>(src2),
                                                  chunk_X2, chunk_Y2, barrier);

    ptx::cp_async_bulk_tensor_2d_global_to_shared(reinterpret_cast<uint64_t *>(dst3),
                                                  reinterpret_cast<const uint64_t *>(src3),
                                                  chunk_X3, chunk_Y3, barrier);

    // Arrive on the barrier and tell how many bytes are expected to come in.
    ptx::mbarrier_arrive_expect_tx(barrier, 3 * num_bytes);
  } else {
    // Other threads just arrive
    ptx::mbarrier_arrive(barrier);
  }
#endif  // #if (defined __CUDA_ARCH__) && (__CUDA_ARCH__ >= 1000)
}

}  // namespace
}  // namespace transformer_engine

#endif  // TRANSFORMER_ENGINE_PTX_CUH_