libc/startup/gpu/nvptx/start.cpp

   1 //===-- Implementation of crt for nvptx -----------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "src/__support/GPU/utils.h"
  10 #include "src/__support/RPC/rpc_client.h"
  11 #include "src/stdlib/atexit.h"
  12 #include "src/stdlib/exit.h"
  13
  14 extern "C" int main(int argc, char **argv, char **envp);
  15
  16 namespace LIBC_NAMESPACE {
  17
  18 extern "C" {
  19 // Nvidia's 'nvlink' linker does not provide these symbols. We instead need
  20 // to manually create them and update the globals in the loader implememtation.
  21 uintptr_t *__init_array_start [[gnu::visibility("protected")]];
  22 uintptr_t *__init_array_end [[gnu::visibility("protected")]];
  23 uintptr_t *__fini_array_start [[gnu::visibility("protected")]];
  24 uintptr_t *__fini_array_end [[gnu::visibility("protected")]];
  25 }
  26
  27 using InitCallback = void(int, char **, char **);
  28 using FiniCallback = void(void);
  29
  30 static void call_init_array_callbacks(int argc, char **argv, char **env) {
  31   size_t init_array_size = __init_array_end - __init_array_start;
  32   for (size_t i = 0; i < init_array_size; ++i)
  33     reinterpret_cast<InitCallback *>(__init_array_start[i])(argc, argv, env);
  34 }
  35
  36 static void call_fini_array_callbacks() {
  37   size_t fini_array_size = __fini_array_end - __fini_array_start;
  38   for (size_t i = 0; i < fini_array_size; ++i)
  39     reinterpret_cast<FiniCallback *>(__fini_array_start[i])();
  40 }
  41
  42 } // namespace LIBC_NAMESPACE
  43
  44 extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
  45 _begin(int argc, char **argv, char **env) {
  46   // We want the fini array callbacks to be run after other atexit
  47   // callbacks are run. So, we register them before running the init
  48   // array callbacks as they can potentially register their own atexit
  49   // callbacks.
  50   LIBC_NAMESPACE::atexit(&LIBC_NAMESPACE::call_fini_array_callbacks);
  51   LIBC_NAMESPACE::call_init_array_callbacks(argc, argv, env);
  52 }
  53
  54 extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
  55 _start(int argc, char **argv, char **envp, int *ret) {
  56   // Invoke the 'main' function with every active thread that the user launched
  57   // the _start kernel with.
  58   __atomic_fetch_or(ret, main(argc, argv, envp), __ATOMIC_RELAXED);
  59 }
  60
  61 extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
  62 _end(int retval) {
  63   // To finis the execution we invoke all the callbacks registered via 'atexit'
  64   // and then exit with the appropriate return value.
  65   LIBC_NAMESPACE::exit(retval);
  66 }