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
14extern "C" int main(int argc, char **argv, char **envp);
15
16namespace LIBC_NAMESPACE {
17
18extern "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.
21uintptr_t *__init_array_start [[gnu::visibility("protected")]];
22uintptr_t *__init_array_end [[gnu::visibility("protected")]];
23uintptr_t *__fini_array_start [[gnu::visibility("protected")]];
24uintptr_t *__fini_array_end [[gnu::visibility("protected")]];
25}
26
27// Nvidia requires that the signature of the function pointers match. This means
28// we cannot support the extended constructor arguments.
29using InitCallback = void(void);
30using FiniCallback = void(void);
31
32static void call_init_array_callbacks(int, char **, char **) {
33 size_t init_array_size = __init_array_end - __init_array_start;
34 for (size_t i = 0; i < init_array_size; ++i)
35 reinterpret_cast<InitCallback *>(__init_array_start[i])();
36}
37
38static void call_fini_array_callbacks() {
39 size_t fini_array_size = __fini_array_end - __fini_array_start;
40 for (size_t i = fini_array_size; i > 0; --i)
41 reinterpret_cast<FiniCallback *>(__fini_array_start[i - 1])();
42}
43
44} // namespace LIBC_NAMESPACE
45
46extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
47_begin(int argc, char **argv, char **env) {
48 // We want the fini array callbacks to be run after other atexit
49 // callbacks are run. So, we register them before running the init
50 // array callbacks as they can potentially register their own atexit
51 // callbacks.
52 LIBC_NAMESPACE::atexit(&LIBC_NAMESPACE::call_fini_array_callbacks);
53 LIBC_NAMESPACE::call_init_array_callbacks(argc, argv, env);
54}
55
56extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
57_start(int argc, char **argv, char **envp, int *ret) {
58 // Invoke the 'main' function with every active thread that the user launched
59 // the _start kernel with.
60 __atomic_fetch_or(ret, main(argc, argv, envp), __ATOMIC_RELAXED);
61}
62
63extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
64_end(int retval) {
65 // To finis the execution we invoke all the callbacks registered via 'atexit'
66 // and then exit with the appropriate return value.
67 LIBC_NAMESPACE::exit(retval);
68}
69

source code of libc/startup/gpu/nvptx/start.cpp