[flang][cuda] Add entry point to launch cuda fortran kernel

Author: clementval

flang/include/flang/Runtime/CUDA/kernel.h

@@ -0,0 +1,29 @@
+//===-- include/flang/Runtime/CUDA/kernel.h ---------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_RUNTIME_CUDA_KERNEL_H_
+#define FORTRAN_RUNTIME_CUDA_KERNEL_H_
+
+#include "flang/Runtime/entry-names.h"
+#include <cstddef>
+#include <stdint.h>
+
+namespace Fortran::runtime::cuda {
+
+extern "C" {
+
+// This function uses intptr_t instead of CUDA's unsigned int to match
+// the type of MLIR's index type. This avoids the need for casts in the
+// generated MLIR code.
+void RTDEF(CUFLaunchKernel)(const void *kernelName, intptr_t gridX,
+    intptr_t gridY, intptr_t gridZ, intptr_t blockX, intptr_t blockY,
+    intptr_t blockZ, int32_t smem, void **params, void **extra);
+
+} // extern "C"
+
+} // namespace Fortran::runtime::cuda

flang/runtime/CUDA/CMakeLists.txt

@@ -17,6 +17,7 @@ add_flang_library(${CUFRT_LIBNAME}
   allocator.cpp
   allocatable.cpp
   descriptor.cpp
+  kernel.cpp
   memory.cpp
   registration.cpp
 )

flang/runtime/CUDA/kernel.cpp

@@ -0,0 +1,37 @@
+//===-- runtime/CUDA/kernel.cpp -------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Runtime/CUDA/kernel.h"
+#include "../terminator.h"
+#include "flang/Runtime/CUDA/common.h"
+
+#include "cuda_runtime.h"
+
+namespace Fortran::runtime::cuda {
+
+extern "C" {
+
+void RTDEF(CUFLaunchKernel)(const void *kernel, intptr_t gridX, intptr_t gridY,
+    intptr_t gridZ, intptr_t blockX, intptr_t blockY, intptr_t blockZ,
+    int32_t smem, void **params, void **extra) {
+  dim3 gridDim;
+  gridDim.x = gridX;
+  gridDim.y = gridY;
+  gridDim.z = gridZ;
+  dim3 blockDim;
+  blockDim.x = blockX;
+  blockDim.y = blockY;
+  blockDim.z = blockZ;
+  cudaStream_t stream = 0;
+  CUDA_REPORT_IF_ERROR(
+      cudaLaunchKernel(kernel, gridDim, blockDim, params, smem, stream));
+}
+
+} // extern "C"
+
+} // namespace Fortran::runtime::cuda