[LLVM] Port 'llvm-gpu-loader' to use LLVMOffload

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -87,7 +87,6 @@ function(_get_hermetic_test_compile_options output_var)
          -mcode-object-version=${LIBC_GPU_CODE_OBJECT_VERSION})
   elseif(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
     list(APPEND compile_options
-         "SHELL:-mllvm -nvptx-emit-init-fini-kernel=false"
          -Wno-multi-gpu --cuda-path=${LIBC_CUDA_ROOT}
          -nogpulib -march=${LIBC_GPU_TARGET_ARCHITECTURE} -fno-use-cxa-atexit)
   endif()
@@ -637,6 +636,7 @@ function(add_integration_test test_name)
   # makes `add_custom_target` construct the correct command and execute it.
   set(test_cmd
       ${INTEGRATION_TEST_ENV}
+      $<$<BOOL:${LIBC_TARGET_ARCHITECTURE_IS_NVPTX}>:LIBOMPTARGET_STACK_SIZE=3072>
       $<$<BOOL:${LIBC_TARGET_OS_IS_GPU}>:${gpu_loader_exe}>
       ${CMAKE_CROSSCOMPILING_EMULATOR}
       ${INTEGRATION_TEST_LOADER_ARGS}
@@ -790,8 +790,7 @@ function(add_libc_hermetic test_name)
   if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
     target_link_options(${fq_build_target_name} PRIVATE
       ${LIBC_COMPILE_OPTIONS_DEFAULT} -Wno-multi-gpu
-      -mcpu=${LIBC_GPU_TARGET_ARCHITECTURE} -flto
-      "-Wl,-mllvm,-amdgpu-lower-global-ctor-dtor=0" -nostdlib -static
+      -mcpu=${LIBC_GPU_TARGET_ARCHITECTURE} -flto -nostdlib -static
       "-Wl,-mllvm,-amdhsa-code-object-version=${LIBC_GPU_CODE_OBJECT_VERSION}")
   elseif(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
     target_link_options(${fq_build_target_name} PRIVATE
@@ -859,6 +858,7 @@ function(add_libc_hermetic test_name)
       string(REPLACE " " ";" test_cmd "${test_cmd_parsed}")
     else()
       set(test_cmd ${HERMETIC_TEST_ENV}
+        $<$<BOOL:${LIBC_TARGET_ARCHITECTURE_IS_NVPTX}>:LIBOMPTARGET_STACK_SIZE=3072>
         $<$<BOOL:${LIBC_TARGET_OS_IS_GPU}>:${gpu_loader_exe}> ${CMAKE_CROSSCOMPILING_EMULATOR} ${HERMETIC_TEST_LOADER_ARGS}
         $<TARGET_FILE:${fq_build_target_name}> ${HERMETIC_TEST_ARGS})
     endif()

libc/startup/gpu/amdgpu/start.cpp

@@ -13,6 +13,9 @@
 #include "src/stdlib/atexit.h"
 #include "src/stdlib/exit.h"
 
+// TODO: Merge this and the NVPTX start files once the common `device_kernel`
+// attribute correctly implies `amdgpu_kernel`.
+
 extern "C" int main(int argc, char **argv, char **envp);
 extern "C" void __cxa_finalize(void *dso);
 
@@ -21,45 +24,18 @@ namespace LIBC_NAMESPACE_DECL {
 // FIXME: Factor this out into common logic so we don't need to stub it here.
 void teardown_main_tls() {}
 
-// FIXME: Touch this symbol to force this to be linked in statically.
-volatile void *dummy = &LIBC_NAMESPACE::rpc::client;
-
 DataEnvironment app;
 
-extern "C" uintptr_t __init_array_start[];
-extern "C" uintptr_t __init_array_end[];
-extern "C" uintptr_t __fini_array_start[];
-extern "C" uintptr_t __fini_array_end[];
-
-using InitCallback = void(int, char **, char **);
-using FiniCallback = void(void);
-
-static void call_init_array_callbacks(int argc, char **argv, char **env) {
-  size_t init_array_size = __init_array_end - __init_array_start;
-  for (size_t i = 0; i < init_array_size; ++i)
-    reinterpret_cast<InitCallback *>(__init_array_start[i])(argc, argv, env);
-}
-
-static void call_fini_array_callbacks() {
-  size_t fini_array_size = __fini_array_end - __fini_array_start;
-  for (size_t i = fini_array_size; i > 0; --i)
-    reinterpret_cast<FiniCallback *>(__fini_array_start[i - 1])();
-}
-
 } // namespace LIBC_NAMESPACE_DECL
 
 extern "C" [[gnu::visibility("protected"), clang::amdgpu_kernel,
              clang::amdgpu_flat_work_group_size(1, 1),
              clang::amdgpu_max_num_work_groups(1)]] void
-_begin(int argc, char **argv, char **env) {
+_begin(int, char **, char **env) {
+  // The LLVM offloading runtime will automatically call any present global
+  // constructors and destructors so we defer that handling.
   __atomic_store_n(&LIBC_NAMESPACE::app.env_ptr,
                    reinterpret_cast<uintptr_t *>(env), __ATOMIC_RELAXED);
-  // We want the fini array callbacks to be run after other atexit
-  // callbacks are run. So, we register them before running the init
-  // array callbacks as they can potentially register their own atexit
-  // callbacks.
-  LIBC_NAMESPACE::atexit(&LIBC_NAMESPACE::call_fini_array_callbacks);
-  LIBC_NAMESPACE::call_init_array_callbacks(argc, argv, env);
 }
 
 extern "C" [[gnu::visibility("protected"), clang::amdgpu_kernel]] void

libc/startup/gpu/nvptx/start.cpp

@@ -23,48 +23,14 @@ DataEnvironment app;
 // FIXME: Factor this out into common logic so we don't need to stub it here.
 void teardown_main_tls() {}
 
-// FIXME: Touch this symbol to force this to be linked in statically.
-volatile void *dummy = &LIBC_NAMESPACE::rpc::client;
-
-extern "C" {
-// Nvidia's 'nvlink' linker does not provide these symbols. We instead need
-// to manually create them and update the globals in the loader implememtation.
-uintptr_t *__init_array_start [[gnu::visibility("protected")]];
-uintptr_t *__init_array_end [[gnu::visibility("protected")]];
-uintptr_t *__fini_array_start [[gnu::visibility("protected")]];
-uintptr_t *__fini_array_end [[gnu::visibility("protected")]];
-}
-
-// Nvidia requires that the signature of the function pointers match. This means
-// we cannot support the extended constructor arguments.
-using InitCallback = void(void);
-using FiniCallback = void(void);
-
-static void call_init_array_callbacks(int, char **, char **) {
-  size_t init_array_size = __init_array_end - __init_array_start;
-  for (size_t i = 0; i < init_array_size; ++i)
-    reinterpret_cast<InitCallback *>(__init_array_start[i])();
-}
-
-static void call_fini_array_callbacks() {
-  size_t fini_array_size = __fini_array_end - __fini_array_start;
-  for (size_t i = fini_array_size; i > 0; --i)
-    reinterpret_cast<FiniCallback *>(__fini_array_start[i - 1])();
-}
-
 } // namespace LIBC_NAMESPACE_DECL
 
 extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
-_begin(int argc, char **argv, char **env) {
+_begin(int, char **, char **env) {
+  // The LLVM offloading runtime will automatically call any present global
+  // constructors and destructors so we defer that handling.
   __atomic_store_n(&LIBC_NAMESPACE::app.env_ptr,
                    reinterpret_cast<uintptr_t *>(env), __ATOMIC_RELAXED);
-
-  // We want the fini array callbacks to be run after other atexit
-  // callbacks are run. So, we register them before running the init
-  // array callbacks as they can potentially register their own atexit
-  // callbacks.
-  LIBC_NAMESPACE::atexit(&LIBC_NAMESPACE::call_fini_array_callbacks);
-  LIBC_NAMESPACE::call_init_array_callbacks(argc, argv, env);
 }
 
 extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void

llvm/tools/CMakeLists.txt

@@ -9,10 +9,6 @@
 # traversing each directory.
 create_llvm_tool_options()
 
-if(NOT LLVM_COMPILER_IS_GCC_COMPATIBLE OR NOT LLVM_LIBC_GPU_BUILD)
-  set(LLVM_TOOL_LLVM_GPU_LOADER_BUILD OFF)
-endif()
-
 if(NOT LLVM_BUILD_LLVM_DYLIB AND NOT LLVM_BUILD_LLVM_C_DYLIB)
   set(LLVM_TOOL_LLVM_SHLIB_BUILD Off)
 endif()

llvm/tools/llvm-gpu-loader/CMakeLists.txt

@@ -1,46 +1,12 @@
 set(LLVM_LINK_COMPONENTS
-  BinaryFormat
-  Object
   Option
   Support
-  FrontendOffloading
   TargetParser
 )
 
 add_llvm_tool(llvm-gpu-loader
   llvm-gpu-loader.cpp
 
-  # TODO: We intentionally split this currently due to statically linking the
-  #       GPU runtimes. Dynamically load the dependencies, possibly using the
-  #       LLVM offloading API when it is complete.
-  PARTIAL_SOURCES_INTENDED
-
   DEPENDS
   intrinsics_gen
 )
-
-# Locate the RPC server handling interface.
-include(FindLibcCommonUtils)
-target_link_libraries(llvm-gpu-loader PUBLIC llvm-libc-common-utilities)
-
-# Check for HSA support for targeting AMD GPUs.
-find_package(hsa-runtime64 QUIET 1.2.0 HINTS ${CMAKE_INSTALL_PREFIX} PATHS /opt/rocm)
-if(hsa-runtime64_FOUND)
-  target_sources(llvm-gpu-loader PRIVATE amdhsa.cpp)
-  target_compile_definitions(llvm-gpu-loader PRIVATE AMDHSA_SUPPORT)
-  target_link_libraries(llvm-gpu-loader PRIVATE hsa-runtime64::hsa-runtime64)
-
-  # Compatibility with the old amdhsa-loader name.
-  add_llvm_tool_symlink(amdhsa-loader llvm-gpu-loader)
-endif()
-
-# Check for CUDA support for targeting NVIDIA GPUs.
-find_package(CUDAToolkit 11.2 QUIET)
-if(CUDAToolkit_FOUND)
-  target_sources(llvm-gpu-loader PRIVATE nvptx.cpp)
-  target_compile_definitions(llvm-gpu-loader PRIVATE NVPTX_SUPPORT)
-  target_link_libraries(llvm-gpu-loader PRIVATE CUDA::cuda_driver)
-
-  # Compatibility with the old nvptx-loader name.
-  add_llvm_tool_symlink(nvptx-loader llvm-gpu-loader)
-endif()