[libc-commits] [libc] [llvm] [LLVM] Port 'llvm-gpu-loader' to use LLVMOffload (PR #162739)

[Joseph Huber via libc-commits]

================
@@ -1,108 +1,177 @@
-//===-- Generic device loader interface -----------------------------------===//
+//===-- Dynamically loaded offload API ------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
+//
+// Dynamically loads the API provided by the LLVMOffload library. We need to do
+// this dynamically because this tool is used before it is actually built and
+// should be provided even when the user did not specify the offload runtime.
+//
+//===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TOOLS_LLVM_GPU_LOADER_LLVM_GPU_LOADER_H
 #define LLVM_TOOLS_LLVM_GPU_LOADER_LLVM_GPU_LOADER_H
 
-#include <cstddef>
-#include <cstdint>
-#include <cstdio>
-#include <cstdlib>
-#include <cstring>
-
-/// Generic launch parameters for configuration the number of blocks / threads.
-struct LaunchParameters {
-  uint32_t num_threads_x;
-  uint32_t num_threads_y;
-  uint32_t num_threads_z;
-  uint32_t num_blocks_x;
-  uint32_t num_blocks_y;
-  uint32_t num_blocks_z;
-};
-
-/// The arguments to the '_begin' kernel.
-struct begin_args_t {
-  int argc;
-  void *argv;
-  void *envp;
-};
-
-/// The arguments to the '_start' kernel.
-struct start_args_t {
-  int argc;
-  void *argv;
-  void *envp;
-  void *ret;
-};
-
-/// The arguments to the '_end' kernel.
-struct end_args_t {};
-
-/// Generic interface to load the \p image and launch execution of the _start
-/// kernel on the target device. Copies \p argc and \p argv to the device.
-/// Returns the final value of the `main` function on the device.
-#ifdef AMDHSA_SUPPORT
-int load_amdhsa(int argc, const char **argv, const char **evnp, void *image,
-                size_t size, const LaunchParameters &params,
-                bool print_resource_usage);
-#endif
-#ifdef NVPTX_SUPPORT
-int load_nvptx(int argc, const char **argv, const char **evnp, void *image,
-               size_t size, const LaunchParameters &params,
-               bool print_resource_usage);
-#endif
-
-/// Return \p V aligned "upwards" according to \p Align.
-template <typename V, typename A> inline V align_up(V val, A align) {
-  return ((val + V(align) - 1) / V(align)) * V(align);
-}
-
-/// Copy the system's argument vector to GPU memory allocated using \p alloc.
-template <typename Allocator>
-void *copy_argument_vector(int argc, const char **argv, Allocator alloc) {
-  size_t argv_size = sizeof(char *) * (argc + 1);
-  size_t str_size = 0;
-  for (int i = 0; i < argc; ++i)
-    str_size += strlen(argv[i]) + 1;
-
-  // We allocate enough space for a null terminated array and all the strings.
-  void *dev_argv = alloc(argv_size + str_size);
-  if (!dev_argv)
-    return nullptr;
-
-  // Store the strings linerally in the same memory buffer.
-  void *dev_str = reinterpret_cast<uint8_t *>(dev_argv) + argv_size;
-  for (int i = 0; i < argc; ++i) {
-    size_t size = strlen(argv[i]) + 1;
-    std::memcpy(dev_str, argv[i], size);
-    static_cast<void **>(dev_argv)[i] = dev_str;
-    dev_str = reinterpret_cast<uint8_t *>(dev_str) + size;
-  }
-
-  // Ensure the vector is null terminated.
-  reinterpret_cast<void **>(dev_argv)[argc] = nullptr;
-  return dev_argv;
-}
-
-/// Copy the system's environment to GPU memory allocated using \p alloc.
-template <typename Allocator>
-void *copy_environment(const char **envp, Allocator alloc) {
-  int envc = 0;
-  for (const char **env = envp; *env != 0; ++env)
-    ++envc;
-
-  return copy_argument_vector(envc, envp, alloc);
-}
-
-inline void handle_error_impl(const char *file, int32_t line, const char *msg) {
-  fprintf(stderr, "%s:%d:0: Error: %s\n", file, line, msg);
-  exit(EXIT_FAILURE);
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/Error.h"
+
+typedef enum ol_alloc_type_t {
+  OL_ALLOC_TYPE_HOST = 0,
+  OL_ALLOC_TYPE_DEVICE = 1,
+  OL_ALLOC_TYPE_FORCE_UINT32 = 0x7fffffff
----------------
jhuber6 wrote:

1. Because the header is autogenerated *after* LLVM builds
2. We don't, but the idea is that this will be ABI stable from now until the future (Still 0.0 right now)
3. Even if we dependended on the headers we'd still need the dynamic interface to make this a common LLVM tool (since I use it for testing)

There should be a bit of an explanation in the file header comment, but I can make it more verbose.

https://github.com/llvm/llvm-project/pull/162739